Citation
Carbon Supply and Demand in an Annual Raspberry (Rubus idaeus L.) Cropping System

Material Information

Title:
Carbon Supply and Demand in an Annual Raspberry (Rubus idaeus L.) Cropping System
Creator:
RAYA, HORACIO ELISEO ALVARADO
Copyright Date:
2008

Subjects

Subjects / Keywords:
Canes ( jstor )
Cultural preservation ( jstor )
Floricanes ( jstor )
Fruiting ( jstor )
Fruits ( jstor )
Plant roots ( jstor )
Primocanes ( jstor )
Production technology ( jstor )
Raspberries ( jstor )
Root pruning ( jstor )
Miami metropolitan area ( local )

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright Horacio Eliseo Alvarado Raya. Permission granted to University of Florida to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Embargo Date:
8/31/2006
Resource Identifier:
496808833 ( OCLC )

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Full Text












CARBON SUPPLY AND DEMAND IN AN ANNUAL RASPBERRY (Rubus idaeus
L.) CROPPING SYSTEM















By

HORACIO ELISEO ALVARADO RAYA


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


2006

































Copyright 2005

by

Horacio Eliseo Alvarado Raya

































This dissertation is dedicated with love to my wife, Maria Eugenia, and my daughter and
son, Lorena and Erandi.















ACKNOWLEDGMENTS

I thank the members of my committee -Dr. Rebecca L. Damell, Dr. Jeffery G.

Williamson, Dr. Steven A. Sargent, Dr. Jonathan H. Crane and Dr. Jerry A. Bartz- for

their guidance and support during my studies. I especially thank Dr. Darnell for her

encouragement and endless willingness to teach and help. I thank Steven Hiss for his

limitless help during my studies. I also thank Paul Miller for his advises and help during

my research. I want to thank Nicacio Cruz-Huerta for his unselfish readiness to discuss

and help during my research. I also would like to thank all my friends in "Mexicans in

Gainesville" for their support during our first days in Gainesville and their company

during our spare time; I thank them for all those precious memories.

I want to especially thank the people of Mexico who economically supported my

studies through the Mexican Council for Science and Technology (CONACyT). I also

want to thank the staff in CONACyT and my colleagues in the Universidad Autonoma

Chapingo.

Finally, I want to thank my parents (Francisca Raya and Delfino Alvarado) for

being my guide and inspiration, and my brothers and sister (Angel, Erendira, Humberto

and Heraclio) for their endless love.
















TABLE OF CONTENTS

page

A C K N O W L E D G M E N T S ................................................................................................. iv

LIST OF TABLES ............... .... .................................... .. .............. viii

LIST OF FIGURES ............................... ... ...... ... ................. .x

ABSTRACT .............. .................. .......... .............. xi

CHAPTER

1 IN TRODU CTION ................................................. ...... .................

2 LITER A TU R E REV IEW ............................................................. ....................... 5

Bram ble Taxonom y ....................... .... ......................................... .... .5
R raspberry M orphology ............................................................. .............. ............. 6
R raspberry Phenology .................. ...................................... .. ........ ....
R aspb erry P rodu action .................................................... ....................................... 10
Plant D ensity in R aspberry ...................................................... ....................... 11
Alternative Cropping Systems in Raspberry ................................... ............... 14
Raspberry Cropping in Mild-winter Areas.....................................................16
Root Pruning Effect on Yield ............................................................................17

3 EFFECTS OF IN-ROW PLANTING DISTANCE ON YIELD IN A WINTER
RASPBERRY (Rubus idaeus L.) PRODUCTION SYSTEM............................... 21

M materials an d M eth od s .................................................................... .....................2 3
P lant M material ...............................................................2 3
Planting System ............................................................24
P lant G row th ........................... ................................................ .......... .25
Fruit Chemical Analysis. ............................................... ......... 26
E x p erim ental D esign ..................................................................................... 2 6
Results ............................ ................................. 26
Flowering .......................... .....................27
F ru itin g ...............................................................2 7
Yield Components ............. ......... ......... .........28
F ru it Q u ality ................................................................2 9
Discussion ..................................................29


v









C u ltiv ars ................................................................... 2 9
In -row Sp acin g .............................................................. 3 1
C onclu sion ...................................................................................................... 34

4 EFFECT OF INTENSITY AND TIMING OF GIRDLING ON WINTER
RASPBERRY (Rubus idaeus L.) PRODUCTION.........................................39

M materials an d M eth od s .................................................................... .....................42
P lant M material ......................................................................42
P la n t G ro w th .................................................................................................. 4 3
Girdling ................. .............................. 44
E x p erim ental D esign ........................................ ............................................44
Results ............ ....... ..................................45
Flowering ............... ......... .......................45
F ru itin g ...............................................................4 6
Yield Components ............. ......... ......... .........47
D ry W eight A location ............................................................. 47
F ru it Q u ality ................................................................4 8
D discussion .................................................................................. ........ .......... ..... .... 48
Bloom and Fruiting Period ............................................ ................48
Y field Com ponents ......... ................ .... ......... ....... ..... ... .... 49
D ry W eight A location ........................................ ................................. 51
F ru it Q u ality ............................................................................................ 5 2
C o n c lu sio n .............. ......... ................................................ .. ....5 3

5 EFFECT OF PRIMOCANE REMOVAL AND FLORICANE GIRDLING ON
'TULAMEEN' RED RASPBERRY (Rubus idaeus L.) YIELD IN A WINTER
PR O D U C TIO N SY STE M ............................................................... .....................60

M materials and M methods ....................................................................... ..................62
P lant M material ...............................................................62
G irdling and C ane R em oval ........................................ .......................... 63
R productive M easurem ents ........................................ .......... ............... 64
Photosynthesis ................................. .......................... .... ...... 64
E x p erim ental D esign ........................................ ............................................64
R e su lts ...........................................................................................6 5
D isc u ssio n ............................................................................................................. 6 6
C conclusion ...................................................................................................... ....... 68

6 ROOT PRUNING EFFECTS ON GROWTH AND YIELD OF RED
RA SPBERRY (Rubus idaeus L.) ....................................................... 73

M materials an d M eth od s ......................................................................................... 7 5
P lant M material ...............................................................7 5
P h o to sy n th e sis ............................................................................................... 7 7
Carbohydrate A analysis ................................................. ........ 77
E x p erim ental D esig n ..................................................................................... 7 8









R e su lts .................................................................................................................... 7 8
D isc u ssio n .............................................................................................................. 8 1
C conclusion ....................................................................................................... ........ 83

7 SUMMARY AND CONCLUSIONS.......................................................................88

APPENDIX

A YIELD PER AREA IN WINTER 2003 ............................................ ............... 91

B D AILY TEM PERA TURES............................................... ............................... 92

L IST O F R E FE R E N C E S ............................................................................. .............. 95

BIOGRAPHICAL SKETCH .............................................................. ...............104















LIST OF TABLES


Table p

3-1 Flowering of 'Heritage' and 'Tulameen' red raspberry as affected by in-row
spacings in a winter production system in North Florida......................................37

3-2 Fruit harvest period in 'Heritage' and 'Tulameen' red as affected by in-row
spacings in a winter production system in North Florida......................................37

3-3 Reproductive development in 'Heritage' and 'Tulameen' red raspberry as
affected by in-row spacing in a winter production system in North Florida............ 38

3-4 Fruit quality in 'Heritage' and 'Tulameen' red raspberry as affected by in-row
spacing in a winter production system in North Florida.......................................38

4-1 Flowering of 'Willamette' and 'Tulameen' red raspberry as affected by 75%
girdling in a winter production system in North Florida............... ...................54

4-2 Flowering of 'Tulameen' red raspberry as affected by girdling intensity in a
winter production system in North Florida. .................................. .................54

4-3 Flowering of 'Willamette' red raspberry as affected by girdling intensity in a
winter production system in North Florida. .................................. .................55

4-4 Fruit harvest of 'Willamette' and 'Tulameen' red raspberry as affected by
girdling in a winter production system in North Florida ....................................55

4-5 Fruit harvest of 'Tulameen' red raspberry as affected by girdling intensity in a
winter production system in North Florida. .................................. .................55

4-6 Fruit harvest of 'Willamette' red raspberry as affected by girdling intensity in a
winter production system in North Florida. .................................. .................56

4-7 Yield components of 'Willamette' and 'Tulameen' red raspberry as affected by
75% girdling time in a winter production system in North Florida .......................56

4-8 Yield components for 'Tulameen' red raspberry as affected by girdling time and
intensity in a winter production system in North. ............. ..................................... 57

4-9 Yield components of 'Willamette' red raspberry as affected by girdling time in a
winter production system in North Florida. .................................. .................57









4-10 Dry weight partitioning in 'Willamette' and 'Tulameen' red raspberry as
affected by girding time in a winter production system in North Florida...............58

4-11 Dry weight partitioning in 'Tulameen' red raspberry as affected by girdling time
and intensity in a winter production system in North Florida ..............................58

4-12 Dry weight allocation pattern in 'Willamette' red raspberry as affected by
girdling time in a winter production system in North Florida ..............................59

4-13 Fruit quality in 'Tulameen' red raspberry as affected by girdling time and
intensity in a winter production system in North-Florida ....................................59

5-1 Effect of girdling and primocane removal on bloom and fruiting in 'Tulameen'
red raspberry in a winter production system... ................... ......................... 71

5-2 Effect of girdling and primocane removal on yield components of 'Tulameen'
red raspberry in a winter production system... ................... ......................... 71

5-3 Effect of girdling and primocane removal on dry weight allocation in
'Tulameen' red raspberry in a winter production system .....................................71

5-4 Effect of girdling and primocane removal on leaf photosynthesis (itmol CO2'm
2sl-1) of 'Tulameen' red raspberry in a winter production system............................71

5-5 Effect of girdling and primocane removal in 'Tulameen' raspberry fruit quality
in a w inter production system ............................................................................ 72

6-1 Effect of dormant root pruning on dry weight allocation in 'Cascade Delight' red
raspberry in a winter production system in north Florida.....................................84

6-2 Effect of dormant root pruning on yield components of 'Cascade Delight' red
raspberry in a winter production system in North Florida....................................84

6-3 Effect of dormant root pruning on fruit quality of 'Cascade Delight' red
raspberry in a winter production system ...................................... ............... 84

6-4 Effect of dormant root pruning on leaf photosynthesis Pn of 'Cascade Delight'
red raspberry in a winter production system in North Florida. ..............................85

6-5 Effect of root pruning and harvest time on carbohydrate concentration of
'Cascade Delight' red raspberry in a winter production system in North Florida ..86

6-6 Effect of root pruning and harvest time on total carbohydrate concentration of
'Cascade D light' .....................................................................87

A-1 Maximum estimated yield per area obtained in an annual winter cropping
system in North Florida and its comparison with previously reported yield. .........91















LIST OF FIGURES


Figure p

3-1 Flowering in 'Heritage' and 'Tulameen' red raspberry planted at in-row
spacings of 25 (A) or 50 cm (B) in a winter production in North Florida (2002)....35

3-2 Fruiting in 'Heritage' and 'Tulameen' red raspberry planted at in-row spacings
of 25 (A) or 50 cm (B) in a winter production in North Florida (2002). ................36

5-1 Effect of girdling and primocane removal on bloom (A) and fruiting (B) in
'Tulameen' red raspberry in a winter production system. .......................................70

B-l Day, night and daily average temperatures in tunnel during 2002 raspberry crop
season in North Florida. Fruit harvest from 28 Feb to 16 May.............................92

B-2 Day, night and daily average temperatures in tunnel during 2003 raspberry crop
season in North Florida. Fruit harvest from 11 Feb to 14 May.............................93

B-3 Day, night and daily average temperatures in tunnel during 2004 raspberry crop
season in North Florida. Fruit harvest from 14 May to 12 July.............................94















Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

CARBON SUPPLY AND DEMAND IN AN ANNUAL RASPBERRY (Rubus idaeus
L.) CROPPING SYSTEM

By

Horacio E. Alvarado Raya

August 2006

Chair: Rebecca L. Darnell
Cochair: Jeffery G. Williamson
Major Department: Horticultural Science

As the interest in raspberry out-of-season production increases, lucrative cropping

systems need to be developed. This research studied the feasibility of an annual winter

cropping system for raspberry in northern Florida. Bare-root canes of the fall-bearing

'Heritage' and summer-bearing 'Tulameen' were shipped during fall 2001 from

northwestern nurseries in the U.S. Canes were planted in a polyethylene tunnel in

December at either 25 or 50 cm in-row spacing. Fruit harvest began in March 2002.

'Tulameen' had higher yields per cane due to larger fruit size, better fruit quality and a

shorter harvest period than 'Heritage'. Yield per cane decreased while yield per area

increased by reducing in-row spacings. However, yield in both cultivars appeared

reduced compared with previous work and below the national average of 10 ton/ha.

Because root pruning during plant removal from the nursery is necessary for annual

cropping systems, further experiments were conducted to determine the importance of

root carbohydrates on floricane yield.









Canes of summer-bearing cultivars 'Tulameen' and 'Willamette' were completely

girdled (100%), partially girdled (75%), or non-girdled. Partial girdling had no effect on

floricane yield components or growth. Complete girdling reduced cane flower number in

'Tulameen' and resulted in cane mortality in 'Willamette'. In 'Tulameen', girdling done

at the beginning of bloom decreased fruit number and yield per cane compared with the

non-girdled control but had no effect on 'Willamette' yield components. In a separate

experiment, girdling 'Tulameen' at the peak of bloom decreased flowering and yield by

-25% compared with the non-girdled control; however, the differences were not

statistically significant. Primocane removal did not affect floricane yield components, but

significantly decreased root dry weight.

In the summer-bearing 'Cascade Delight', dormant root pruning significantly

reduced flower and fruit number and cane yield. Root pruning did not affect root

carbohydrate concentration, but total plant carbohydrate concentration decreased

significantly at budbreak.

The annual raspberry cropping system studied in this research shows potential for

winter production; however, root pruning decreased cane yield. The decrease in the root

carbohydrate pool resulting from root pruning likely had a detrimental effect on late

flower differentiation during budbreak and consequently reduced yield.














CHAPTER 1
INTRODUCTION



The United States was the third largest raspberry producer in 2005, with yields

reaching more than 10 ton/ha (Food and Agriculture Organization Statistical Database

[FAOSTAT], 2005). However, only Washington, Oregon and Californian account for

most of the U.S. raspberry production (United States Department of Agriculture [USDA],

2005). During the last ten years, the total U.S. raspberry demand has exceeded its total

production. From 1994 to 2004, the U.S. annually imported more than 10% of the

raspberries sold in the market, with total values ranging from 9 to 41 million dollars per

year (FAOSTAT, 2005).

The increasing interest in growing raspberries in non-traditional areas results from

the promising profits while filling the void in demand. Additionally, proposed cropping

systems that allow raspberry harvest out of the traditional season (Pritts et al., 1999;

Schloemann, 2001; Dale et al., 2005) may help in overcoming the seasonal low fruit

availability in the market. In south Florida, Knight et al. (1996) proposed an annual

system based on obtaining naturally chilled long canes from nurseries in the Pacific

Northwest and field cropping them that same season under mild winter temperatures.

With this system, fruit harvest began in early March. In northern areas in Florida, where

freezing temperatures are common during winter, polyethylene tunnels (Oliveira et al.,

1996a) can provide plant protection and heat accumulation for early and uniform

flowering (Carew et al., 1999).









Although Knight's system demonstrated technical and biological suitability for

raspberry production in tropical climates; the yield of -1.4 ton/ha in this system was far

below the national average of-10 ton/ha as reported by FAOSTAT (2005).

Selection of the appropriate cultivar and plant density for mild winter climates is

important in order to optimize plant performance and profits. Optimum temperatures for

photosynthesis and growth in raspberry range between 20 and 250 C (Cameron et al.,

1993; Fernandez and Pritts, 1994; Percival et al., 1996; Carew et al., 1999; Stafne et al.,

2001), although there is cultivar variability (Stafne et al., 2001). Similarly, the

appropriate plant density is important for yield and fruit quality. Increasing raspberry

plant densities increase yield per area (Freeman et al., 1989; Vanden Heuvel et al., 2000)

up to an optimum; however, beyond this optimum yields per area decrease (Oliveira et

al., 2004). Additionally, excessively high plant densities can reduce fruit size (Vanden

Heuvel et al., 2000).

Raspberry roots are a reserve for assimilates during winter (Whitney, 1982). In the

annual system proposed for south Florida, roots are severely disturbed when removed

from the nursery for shipping, with a concomitant reduction in the root carbohydrate

pool. This is similar to root pruning, which has been shown to decrease growth and fruit

size in apple (Schupp and Ferree, 1987; 1989), grape (Ferree et al., 1999; Lee and Kang,

1997) and sweet cherry (Webster at al., 1997). The effect of root pruning on hormonal

balance (Schupp and Ferree, 1994), water supply (Geisler and Ferree, 1984; Schupp and

Ferree 1990) and nutrient uptake (Schupp and Ferree, 1990) in apple was temporary and

could not explain the reduction in growth of shoot and fruit in this crop. Geisler and









Ferree (1984) suggested that roots and shoots compete with each other for carbohydrates

after root pruning, causing shoot growth to slow.

Carbohydrates appear to be essential for flower induction and formation in Sinapsis

alba L. (Bodson and Outlaw, 1985), Vaccinium ashei Reade (Darnell, 1991) and

Diospyros kaki L (Ooshiro and Anma, 1998). In raspberry, flower differentiation in

temperate climates begins in the upper cane during the fall previous to production and

continues downwards. Flower formation slows during winter and increases again in the

lower cane in spring, right after budbreak (Williams, 1959; Qingwen and Jinjun, 1998).

Furthermore, the root acts as a source of carbohydrate for the floricane during these late

stages of flower differentiation during budbreak (Whitney, 1982; Fernandez and Pritts,

1993). Raspberry root carbohydrate pool may be reduced as a result of the severe pruning

during cane removal and shipping in an annual system like that proposed for south

Florida, resulting in decreased flower number and yield.

Information on the source-sink relations in raspberry annual systems can be

valuable for the appropriate primocane growing in the nursery during the summer and fall

previous to removal and shipping. Cultural activities in the nursery that increase

assimilates stored in the root can be implemented to guarantee sufficient carbohydrate is

available for production during the same season the canes are removed from the nursery.

Similarly, appropriate cultural/management techniques after canes are planted for

production that same season could help alleviate limitations in root carbohydrates that

otherwise might decrease yield. The objectives of the present study were to 1) determine

the effect of plant density on two raspberry genotypes grown under polyethylene tunnels

in an annual winter production system, 2) determine the importance of roots and






4


primocanes to floricane growth and yield, 3) assess the effects of root pruning on

floricane growth and yield, and 4) assess the effects of root pruning on plant carbohydrate

status during flowering and fruiting.














CHAPTER 2
LITERATURE REVIEW

Bramble Taxonomy

The genus Rubus belongs to the Rosaceae family and is a very diverse taxa. Plants

in this genus vary from herbs to woody plants (Bailey, 1941) and are distributed

worldwide, from tropical to subarctic regions (Thompson, 1995) and from sea level to

more than 4,000 m (Hummer, 1996).

Diversity in the genus Rubus is due to polyploidy, apomixis, and hybridization.

There are disagreements among taxonomists (Thompson, 1995), who classify this genus

into 12 to 15 subgenera (Hummer, 1996) and approximately 740 species, most of them

growing in North America (64%) and Asia (27%) (Gu et al., 1993). Three subgenera

contain most of the diversity in this genus; two of them, Idaeobatus (the raspberries) and

Rubus (the blackberries), are frequently cultivated (Hummer, 1996).

Although polyploidy is very common in Rubus, the species in the subgenus

Idaeobatus are primarily diploid, and their origin is south and southeast Asia and North

America (Thompson, 1995). Of the approximately 200 species registered for Idaeobatus

(Hummer, 1996), Rubusphoenicolasius, R. illecebrosus, R. idaeus (the red and yellow

raspberry), R. strigosus (the wild raspberry), and R. occidentalis (the black raspberry) are

cultivated species (Bailey, 1949).

The red raspberry possibly originated in the Magdalena Islands in the Gulf of St.

Laurence (Bailey, 1941). However, other authors speculate that its center of origin is

southwestern China (Gu et al., 1993) and southern Kazakhstan (Thompson, 1995). Most









of the current red raspberry cultivars originated from crosses between R. idaeus and R.

strigosus, the wild raspberry from North America (Crandall, 1995).

Raspberry Morphology

Most plants in the genus Rubus are shrubs, with perennial root systems and biennial

canes that vary from erect to trailing. The root system depth depends on the genotype and

the soil conditions, with black raspberry root systems averaging approximately 90 cm in

depth (Colby, 1936), and red raspberry root systems averaging 180 cm in depth.

However, 70% of the root dry weight is in the first 25 cm (Dana and Goulart, 1989).

Horizontally, roots can grow up to 3.0 m from the main cane (Andersen et al., 1996) and

are distributed symmetrically in all directions.

Vegetative buds in roots are uncommon in black raspberry but present in red

raspberry, where they are found randomly distributed on roots growing in the top 80 cm

of soil (Colby, 1936). Andersen et al. (1996) found vegetative buds on lateral roots

extending up to 3.0 m from the main cane.

Cane elongation rate may vary, but the rate of node formation is nearly constant;

thus, node number depends on cane length (Jennings and Dale, 1982). Leaves have 3 to 5

leaflets and leaf axils may have one, two or even three buds. Usually, only one bud per

axil breaks and forms a branch called the fruiting lateral. Fruiting laterals have leaves and

a group of flowers (inflorescence) in each leaf axil (Crandall, 1995). Flowers are usually

white, although pink colors exist (Bailey 1949). There are many stamens arranged in two

whorls around the receptacle and about 150 pistils arranged in a spiral on the receptacle

(Crandall, 1995). Approximately 75 to 85 pistils grow and coalesce to form the

commercial berry (Dana and Goulart, 1989). In yellow and red raspberry, the berry

separates from the receptacle when it is harvested and forms a hollow cone. The fruit may









vary in size depending on the genotype. Gu et al. (1993) reported fruit of 0.4 g/berry in

China. Commercial raspberries bear fruits with average weights ranging around 1.5

g/berry (Hanson and Morales, 1997) to 6.0 g/berry (Pritts, 1999).

Raspberry propagates by forming new shoots from adventitious buds on the roots,

as well as from axillary buds on the base of the main cane. Adventitious buds are formed

on the root during cool periods (from October to March in the Northern hemisphere) and

can break during the subsequent fall; however, shoot growth occurs only in spring (Dana

and Gulart, 1989). Axillary buds that form new shoots from the base of the main cane are

called leader buds (Moore and Caldwell, 1985). Leader buds usually bear new shoots

with faster growth rates and greater diameters than shoots from root buds (Dana and

Gulart, 1989).

Once shoot growth begins, the new cane (now called the primocane) continues

laying down nodes, leaves and axillary buds during spring and summer until temperatures

drop below 150 C and days become shorter than 9 hours in the fall (Crandall, 1995;

Williams, 1959). Except for the leader buds, which remain vegetative and will form

primocanes in the following spring, most of the axillary buds on the primocane undergo

floral initiation during summer and fall. Then, in spring, after a period of differentiation,

these buds break and form a fruiting lateral with leaves and axillary inflorescences

(Moore and Caldwell, 1985).

Raspberry Phenology

Raspberry cultivars exhibit two main phenological behaviors: summer bearing and

fall bearing behavior. In summer-bearing raspberries, the primocane grows vegetative

during the spring and summer. In fall, after the cessation of terminal growth of the main

cane, axillary buds undergo transition from vegetative to reproductive. Flower bud









initiation (FBI) and early stages of flower bud differentiation (FBD) occur basipetally

(Dana and Goulart, 1989). In winter, canes become dormant and in the following spring,

FBD is completed, followed by budbreak and flowering (Jennings and Dale, 1982). In

these types of raspberries, fruits ripen from early to mid summer (University of Idaho,

2002).

The beginning of FBI is characterized by a dome-shaped growing point inside the

axillary bud. Later, this dome-shape point begins to produce leaf primordia, each one

with an axillary inflorescence primordium. This process is the inflorescence

differentiation and will form the fruiting lateral. Flower differentiation then follows in

each axillary primordium, beginning with the differentiation of sepal primordial,

followed by the differentiation of petal, stamen and pistil primordia. Anthers and ovules

are formed 2 or 3 days before the inflorescence is noticeable (Huang and Lei, 1998).

Although the time for FBI and FBD is controversial, most authors agree that

summer-bearing raspberries initiate flowers in early autumn (Moore and Caldwell, 1985).

Moore and Caldwell (1985) observed that initiation in Scotland occurs in mid-September

and, two weeks later, the axis of the inflorescence is evident. By late October, flower

primordia were differentiated and anther initials and the perianth ring were evident.

Flower diferentiation ceased during winter dormancy and restarted the following spring

before bud break. Huang and Lei (1998) observed a similar time for flower initiation in

Northeast China; however, development of the terminal inflorescence primordia (future

fruiting lateral) and its axillary inflorescences was slow but continuous during winter

(October to mid-April). Floral primordia were evident after April, when the dormant buds

began to break and form fruiting laterals









In fall-bearing raspberries, FBI and FBD take place during the summer and fall on

the primocane (Moore and Caldwell, 1985). Fruits appear in late summer or autumn on

the tip of the primocane and some nodes below it during the same year of vegetative

growth. This upper-portion of the cane dies after cropping, while the basal portion can

over-winter and bear fruit the following summer as a floricane (Keep, 1988).

In 'Heritage', a fall-bearing red raspberry, the first buds undergoing FBI are located

in nodes 10, 11 and 12 below the cane tip. At this time, the cane may be approximately

50 cm tall. Within three weeks cane height reaches 75 cm and all 12 upper buds may

show floral development (Crandall and Garth, 1981).

The importance of temperature and photoperiod in raspberry FBI and FBD is

controversial. Williams (1960), studying the flowering behavior of the summer-bearing

raspberry 'Malling Promise' in a glasshouse, did not observe FBI when plants were

grown at 15.50 C regardless of the day length. Plants grown at 12.70 C and a 9 hour

photoperiod for six weeks underwent FBI, however plants under the same temperature at

16 hour photoperiod did not. Plants grown at 10 C underwent FBI regardless of the

photoperiod, although plants grown under a 9 hour photoperiod initiated flowers one

week earlier than those under 16 hour photoperiods. Williams concluded that photoperiod

and temperature control the flowering habit of 'Malling Promise' raspberries. However,

Vasilakakis et al. (1980) and Takeda (1993) found that low temperatures are not a

requirement for raspberry FBI. They obtained flowering in 'Heritage' plants exposed to

temperatures above 22 C throughout their development, although lower temperatures

hastened the onset of flowering (Takeda, 1993). Although there is no information

comparing the effects of temperature and photoperiod on FBI and FBD in summer









bearing and fall bearing raspberry cultivars, the data suggest that summer bearing

cultivars are sensitive to temperature and photoperiod, while fall bearing cultivars may be

less sensitive.

Like FBI and FBD, primocane growth is under temperature control. Williams

(1959) found that cane growth of 'Malling Promise' under two daylengths (9 and 16

hours) was temperature sensitive. Canes grown at 210 C grew continuously during a two

month period regardless of the daylength. In contrast, canes maintained at 100 C grew

less than two centimeters the first 20 days, and then cane growth stopped regardless of

the daylength. This behavior was also observed by Vasilakakis et al. (1980) who obtained

a longer vegetative growth phase in fall-bearing 'Heritage' canes grown at 220 C

compared with canes grown at 70 C. Canes maintained at 220 C flowered at 80 nodes of

growth, while canes grown at 70 C flowered at 28 to 32 nodes of growth. Carew et al.

(1999) observed an optimum node production rate occurring in fall-bearing 'Autumn

Bliss' growing at 220 C; above and below this temperature, node production slowed.

Similarly, plants of fall-bearing 'Autumn Bliss', 'Heritage' and 'Redwing' grew more

and produced more nodes, flowers and fruits as soil temperature increased (Prive et al.,

1993).

Raspberry Production

Since 1997, the United States has been among the six countries with the greatest

cultivation of raspberry and the highest yields per hectare. In 2005, the US had 6,100

hectares of cultivated raspberry, surpassed only by the Russian Federation, Serbia and

Montenegro, and Poland. The yield per area in the U.S. ranked third in 2005, with 10.2

ton/ha (FAOSTAT, 2005). Three states, Washington, Oregon and California, account for









most of the US raspberry production from June to October (USDA, 2005) and the

demand for the product exceeds the domestic production.

Although the United States is the third largest raspberry producer in the world, as

much as 12% of its domestic demand for raspberry fruit in 2004 was met by imports

(FAOSTAT, 2005). Imported raspberry fruits averaged 8,925 tons in 2004 (FAOSTAT,

2005). Most of the imports are arriving from Canada and Chile year-round and from

Mexico from October through May (USDA, 2006).

Increasing the cultivated area and/or the yield of raspberry in U.S. may be options

for increasing the fruit supply by domestic production. Yield increases are obtained by

selecting high yield cultivars or by increasing plant density of the crop.

Plant Density in Raspberry

Row and plant spacing as well as the number of primocanes per plant determine the

cane density in raspberry plantations. Between-row distances vary according to the plant

vigor, trellising system and harvesting method. Though plant vigor depends on varietal

characteristics, variations on climate may influence the plant growth rate. Red raspberry

grows more vigorously in the Pacific Northwest US than in the Northeast US and

Canada, requiring between-row spacings of 2.4 to 3.0 m, while between-row spacings in

the Northeastern U.S. vary from 1.8 to 2.4 m (Crandall, 1995). Plants trained in V and T-

trellis require wider between-row distances than plants trained in upright trellises.

Plantations planted for machine harvest must have between row spacings wide enough to

permit the machine move along the alleys without damaging plants.

In-row planting distances are determined not only by cultivar vigor, but by the

training method. In-row spacing is closer when plants are trained in hedgerows than when









plants are maintained in hills (Crandall, 1995). In either case, the aim is to achieve the

highest yield per area with acceptable fruit quality.

Raspberry yield results from the interaction among several vegetative and

reproductive components, including number of canes per plant (hill), number of plants

per area, number of nodes per cane, percent of fruitful nodes, number of fruits per node,

fruit weight (Hoover et al., 1988) and lateral length (Freeman et al., 1989) From these,

the yield components that most strongly affect marketable yield are number of canes per

hill (Hoover et al., 1988; Freeman et al., 1989; Gundersheim and Pritts, 1989), number of

buds per cane (Gundersheim and Pritts, 1989), lateral length (Freeman et al., 1989) and

number of fruits per node (Hoover et al., 1988). Yield increased significantly in 'Royalty'

purple raspberry by increasing cane density from 4 to 12 canes per hill (Gundersheim and

Pritts, 1991). Vanden Heuvel et al. (2000) found a significant linear increase in yield per

area of 'Titan' red raspberry as cane density increased from 9 to 30 canes per square

meter. Similarly, Freeman et al. (1989) reported that cane number per hill contributed up

to 24% of the total marketable yield in six raspberry culitvars. Increasing cane number

per hill will result in more fruits per area and consequently more yield per meter of row

up to an optimum cane density. Beyond this optimum; however, yield per area will

decrease (Oliveira et al., 2004).

The impact of plant density on total yield usually interacts with other yield

components and compensation among them is common. In 'Heritage' raspberry, yield of

plants at 25 cm in-row spacing was 99% higher than yield in plots with plants spaced at

100 cm (Myers, 1993). In this case, plant density affected yield per area by increasing the

number of fruiting primocanes at the shorter in-row spacings rather than increasing the









yield per cane. Similarly, Vanden Heuvel et al. (2000) found that cane density has a

negative linear effect on fruit size, but increasing the cane density will result in more

fruits per area. Therefore, the selection of the proper number of plants per area should

consider the effect of plant density on related yield components in order to achieve good

yields and acceptable fruit quality.

The increases in raspberry yield obtained by higher cane densities at the expense of

decreases in other yield components make the raspberry plant an interesting system for

studies on carbon mobilization and interplant competition. In "Washington' red

raspberry, hills with either nine or 12 canes yielded more grams fruit per hectare than

hills with six canes; however, there were more fruiting laterals per cane, more fruits per

lateral and consequently more fruits per cane in hills with six canes (Crandall et al.,

1974). Hoover et al. (1988) reported a significant negative correlation (r=-0.491; p=0.05)

between cane density and number of fruits per node in 'Heritage' red raspberry.

However, Myers (1993) reported that in-row spacings of 25, 50 or 100 cm had no effect

on total number of fruiting nodes per primocane in 'Heritage'. Sullivan and Evans (1992)

found a significant negative correlation (r = -0.61 to -0.77) between cane density and

yield per cane in a three-year experiment with four red raspberry cultivars. Similarly,

Myers (1993) and Vanden Heuvel at al. (2000) documented the negative effect of high

plant and cane densities on fruit size of red raspberry. Goulart and Demchak (1993)

found a negative effect of high densities on fruit size of black raspberry. However, even

though high cane densities decrease fruit size and fruit number, increased density often

results in higher yields per area (Myers, 1993; Gundersheim and Pritts, 1991; Vanden

Heuvel et al. 2000).









The harvest season of raspberry is well defined from June to October in the U.S.

Additionally, the perishability of the fruit limits its postharvest storage life. Considering

this situation, despite the increases in yield per area obtained by increasing plant

densities, the availability of raspberry fruit year-round has to be achieved by extending

the harvest season.

Alternative Cropping Systems in Raspberry

Most of the cropping systems that focus on extending the harvest period are based

on the use of chemical products, cultural practices and/or climate simulation to force the

plant to flower in a season different from the normal one, and advance or delay harvest.

Raspberry has been grown in mild-winter conditions, where endodormancy is overcome

by spraying with oil + dinitro-o-cresol (5%), KNO3 (5%), thiourea (1%) or hydrogen

cyanamid (4%) in late winter or early spring. These treatments also advance the

flowering time compared with untreated controls (Snir, 1983). Summer pruning by

cutting the primocanes at different heights and dates during summer and permitting the

remaining buds to sprout and form new primocanes, has been used to advance flowering

and obtain winter fruits in fall-bearing raspberries like 'Heritage', 'Autumn Bliss', and

'Autumn cascade'; however, the date and intensity of pruning are critical for determining

the harvest period and yield (Oliveira et al., 1996a, Oliveira et al., 1996b). 'Autumn

Bliss' canes pruned in early summer and grown in an unheated greenhouse yielded 26.5

to 63.5 g/cane throughout the fall, while those pruned in late summer yielded only 2.1 to

4.8 g/plant during the winter (Oliveira et al., 1996b).

Although growing raspberries in greenhouses allows manipulation of the harvest

season by advancing or delaying flowering, the harvest period must occur when fruit

prices are high in order to recover the investment in energy and infrastructure.









Additionally, the cropping system must produce high yields. Dale et al. (2001) suggest

that earlier fruiting cultivars are more appropriate for winter greenhouse production than

late fruiting cultivars because early cultivars increase the harvest season by merging the

fall harvest period on the primocane with the summer harvest period on the floricane.

Another alternative for raspberry cropping is the use of plants that have been

naturally or artificially chilled, and then grown inside a heated greenhouse during the

winter. Fall-bearing 'Heritage' plants naturally chilled for more than 1000 chilling units

(CU) before moving them into a heated greenhouse in winter flowered in less than three

months; however, the author does not mention the effect of the treatment on fruiting and

yield (Takeda, 1993). Pritts et al. (1999) proposed a technique to grow winter raspberries

in the Northeast United States. Tissue-cultured raspberry plugs were planted in containers

in May, grown outside until mid-December to receive sufficient natural chilling, and then

moved into a heated greenhouse at 13-180 C. Harvest began 10 weeks later in February

and March. After harvest, the plants were transplanted to larger containers and grown

outside again to begin another crop cycle. It was proposed that growers using this

technique could harvest $2000 to $4000 (660 half pints) worth of high quality fresh

winter fruits in a 6.0 x 9.0 m house. This system has already been utilized commercially

and some problems remain to be solved. Pollination was poor because of the low activity

of bees and the investment is not returned until the second year of cropping when yields

increase up to 400% over the first cropping year (Schloemann, 2001).

Although the profitability in Pritts' proposed system makes this technique

attractive, using heated greenhouses through the winter and supplying additional light









elevates cropping costs. This can be overcome if plants are grown in subtropical areas

with mild winters

Raspberry Cropping in Mild-winter Areas

Mild winters in subtropical regions allow earlier harvest of raspberries compared

with traditional cropping systems by using pre-chilled plants in an annual production

system. Knight et al. (1996) purchased pre-chilled 'Heritage' plants from commercial

nurseries in Washington and field planted them in late January in Florida. In floricanes,

harvest occurred from late March through early September and yield averaged 2,112

kg/ha. Primocanes arising from roots in spring fruited from late May through early

September and accounted for 1,460 kg of fruit per hectare. The key point in this system is

to provide plants with suitable temperatures in the nursery in order to break dormancy, as

well as in the field in order to obtain uniform bud break after planting.

Since photoperiod is not a requirement for dormancy release in raspberry (Heide,

1993), temperature becomes the key factor for successful bud break after the chilling

requirement has been met.

Heat units (HU) appear to have an important role in the timing of flowering after

planting. 'Heritage' plants grown at 29/240 C (day/night) flowered two weeks earlier than

those grown at 25/200 C (Lockshin and Elfving, 1981). However, Hoover et al. (1989)

were not able to explain the difference in harvest date between 'Heritage' and 'Redwing'

growing in different locations and different years on a HU accumulation basis, although

they found a high correlation between cane growth and HU. It is likely that an interaction

between genotype and environment affects flowering onset (Jennings, 1979).

Growers producing raspberries in subtropical conditions are faced with potential

problems of high light intensities, temperatures, and humidity effects on plant









development and fruit quality. Raspberry net photosynthesis is optimum at plant

temperatures of 200 C compared with 25 or 180 C (Percival et al., 1996). Average

temperatures in the subtropics exceeds this optimum and high temperature in

combination with high light intensity and low relative humidity reduces raspberry fruit

size and increases the incidence of sunburn, a disorder that results in discolored dry

drupelets in the fruit (Crandall, 1995). Therefore, a balance in light intensity must be

achieved in order to develop fruit color and soluble solids while avoiding detrimental

effects.

Another potential problem that arises in subtropical winter production systems for

raspberry is the disturbance of the root system during digging and transport that may

result in problems with fruit size and quality. Since plants are grown as annuals in this

system, there is little time for the root system to recover before flowering and fruiting

begin. Thus raspberries canes grown in this system may respond as if they were root

pruned.

Root Pruning Effect on Yield

Root pruning may reduce yield by decreasing fruit size or decreasing fruit number

per cane. The effect of root pruning on fruit size will depend on fruit load, the time and

intensity of pruning, cultivar, and water and nutrient supply (Bradlwarter and Knoll,

1996).

Dormant root pruning is commercially used in high density plantations and strongly

reduces vegetative growth, but also fruit size in apple (Schupp and Ferree, 1987; 1989),

grape (Ferree et al., 1999; Lee and Kang, 1997) and sweet cherry (Webster at al., 1997),

but root pruning at the beginning of flowering had no significant effect on apricot fruit

size (Arzani et al., 1999). Similarly, Elfving et al. (1991) found no effect of root pruning









at full bloom on fruit size of 'Macspur McIntosh'/M7 apple. However, Schupp and

Ferree (1989) found a reduction in fruit size, shoot length, leaf size and trunk cross

sectional area in 'Melrose'/M7A apple trees root pruned either during dormancy or at full

bloom, with the strongest reductions found with dormant root pruning.

The root pruning effect on fruit size could be mediated by alterations in hormone

synthesis and transport, water relations, nutrient uptake and/or assimilation and/or

source-sink relationships (Ferree, 1992). However, previous studies have shown the

temporary effect of root pruning on hormonal balance (Schupp and Ferree, 1994), water

supply (Geisler and Ferree, 1984; Schupp and Ferree 1990) and nutrient uptake (Schupp

and Ferree, 1990). Geisler and Ferree (1984) suggested that competition for assimilates

between roots and shoot may cause the reduction in shoot and fruit size in root pruned

apple

Carbohydrate translocation from shoot to root after root pruning was observed in

grape by Ferree et al. (1999). A decrease in cane dry weight and an increase in root dry

weight was observed in root-pruned compared with non root-pruned vines. Root pruning

decreased the starch content in leaf chloroplasts of deblossomed apple trees (Schupp et

al., 1992), possibly due to mobilization of assimilates from shoot to root during the

intense root growth season. In raspberry, roots compete with shoots and fruits for

carbohydrates and can constitute a strong sink during active growth; in this way, they can

limit shoot and fruit growth (Fernandez and Pritts, 1994). Furthermore, raspberry root

regeneration is concomitant with floricane and primocane growth (Atkinson, 1973) and

may be intensive in the region near the cut (Schupp et al. 1992). The potential









carbohydrate translocation from shoot to root after root pruning in raspberry may

negatively impact the fruiting.

Besides the possible root sink activity during active growth, roots may also play a

source role during budbreak. Fernandez and Pritts (1993) found reductions in root dry

matter concomitant with floricane dry matter increases at budbreak. Additionally,

Whitney (1982) observed carbohydrate mobilization in the floricane from the cane to the

newly growing laterals during budbreak. The importance of adequate carbohydrate

supply to floral buds has been demonstrated in Sinapsis alba (Bodson and Outlaw, 1985),

blueberry (Vaccinium ashei) (Darnell, 1991) and persimmon (Diospyros kaki L) (Ooshiro

and Anma, 1998). In raspberry, a decreased carbohydrate pool in the root at budbreak

could decrease flower formation in the lower parts of the floricane, which are initiating

and differentiating during this time (Williams, 1959; Qingwen and Jinjun, 1998).

The effect of root pruning on cane yield and on the source-sink relationship in

raspberry has not been studied. The annual life of the canes and the continuous

generation of primocanes, which increase the competition between shoot and roots for

assimilates, makes raspberries an interesting model for studying source-sink

relationships. In raspberry plants with intact root systems, the leaves nearest the fruiting

lateral are the main source of assimilates for fruits of that same lateral, however, some of

the fixed carbon in primocanes and floricanes is translocated to the roots (Fernandez and

Pritts, 1993; Prive et al., 1994). Roots translocate carbohydrates to the floricane during

budbreak and peak of harvest but they import current year photosynthates from

primocanes and floricanes during the beginning of fruiting (Fernandez and Pritts, 1993).









The annual cropping system of winter raspberry is based upon the use of naturally

or artificially chilled bare root canes that are removed from the nursery and cropped that

same year. The perturbation of the root system during removal from the nursery and

shipping may have similar effects on yield to those observed in other root pruned fruits

(Schupp and Ferree, 1987, 1989; Ferree et al., 1999; Lee and Kang, 1997; Webster at al.,

1997). Information on the effect of root pruning on yield of raspberry plants grown under

this system is necessary in order to develop the best plant management that will result in

maximal fiscal returns for the crop.














CHAPTER 3
EFFECTS OF IN-ROW PLANTING DISTANCE ON YIELD IN A WINTER
RASPBERRY (Rubus idaeus L.) PRODUCTION SYSTEM

In 2005, the United States was the third largest producer of raspberry. Only the

Russian Federation and Serbia and Montenegro surpassed the US in total raspberry

production. The U.S. reported 6,100 hectares of cultivated raspberry in 2005, with yields

up to 10,164 ton/ha. However, these yields are below those reported for Romania (21,000

ton/Ha) and Mexico (12,035 ton/Ha) (FAOSTAT, 2005).

The relatively low yields per area attained in U.S. indicate an unfulfilled yield

potential for raspberry production in this country. Additionally, only Washington, Oregon

and California account for most of the U.S. raspberry production from June to October

(USDA, 2005). This situation makes the total production in this country insufficient to

meet the high domestic demand for this fruit. In order to fulfill the demand, the U.S.

imported 12% of the raspberries sold in 2004, with a total value above $41.4 million

(FAOSTAT, 2005). The U.S. imports raspberries year-round from Chile and Canada,

while Mexico supplies fruits from October through May (USDA, 2006). The high

perishability of raspberry fruits further limits domestic supply of this berry. Fruits cannot

be stored for more than one week and transport requires meticulous technology to avoid

quality losses, resulting in a stationary and localized domestic raspberry production.

Raspberry production out of season and/or in non-traditional growing regions

results in a higher value product that could mitigate the short supply across the country

during the year. The increasing interest in off-season raspberry production, as well as









production in non-traditional regions, is driving the proposal of several new production

systems. In New York, naturally chilled canes are moved to heated greenhouses in the

fall, resulting in fruit harvest during February, when prices can be $6.00 USD/half pint

(Pritts et al., 1999). However, the costs for constructing, maintaining, heating and

ventilating the greenhouses still may make this system prohibitive for small growers.

Raspberry production in subtropical regions may alleviate the high investments for

winter production. Knight at al. (1996) obtained raspberry fruits in South Florida from

late March through early September by purchasing naturally chilled canes from nurseries

in Washington and field planting them in late January. The chilling temperatures in the

nursery followed by the mild winter conditions in south Florida overcame dormancy and

avoided the expense of building and heating a greenhouse, as proposed by Pritts for

Northeast U.S. However, new problems come with these new systems, and they must be

solved in order to maximize revenues for the grower. Selection of the proper cultivar,

planting density, irrigation and fertilization regimes, and pest and disease control

practices are some of the new topics that must be addressed in these production systems.

Planting density will depend to some extent on the cultivar vigor, as the goal is to

achieve the highest yield without negatively affecting fruit quality. In raspberry, yield is

the result of the interaction of several vegetative and reproductive components, such as

cane density, nodes per cane and fruits per node (Hoover et al., 1988; Freeman et al.,

1989; Gundersheim and Pritts, 1989). Increasing cane density from 9 to 30 canes/m2

significantly increased yield per area of 'Titan' red raspberry (Vanden Heuvel et al.,

2000). Yield component analysis revealed that cane number per hill accounted for 25%

of the total marketable yield in several summer bearing red raspberry cultivars (Freeman









et al., 1989). In a three year experiment with 'Heritage' red raspberry, yield the first year

at 25 cm in-row spacings was 99% higher than yields at 100 cm in-row spacings, with no

differences in yield the following two years (Myers, 1993). However, the yield increase

resulted from an increase in fruit number per area rather than an increase in cane yield,

which typically decreases by increasing cane densities (Sullivan and Evans, 1992;

Vanden Heuvel et al., 2000). Decrease in cane yield with increasing planting density is

apparently due to a decrease in fruit size (Myers, 1993; Goulart and Demchak, 1993;

Vanden Heuvel et al., 2000).

Planting density may also affect fruit chemical composition by altering the amount

of light reaching the fruiting laterals and developing fruits. Fruit soluble solids decreased

and fruit pH increased on partially shaded laterals of hedgerow planted canes compared

with better light exposed laterals of V-trellised canes (Vanden Heuvel et al., 2000).

In an annual winter raspberry production system in subtropical climates, the proper

cultivar and planting density is important in order to maximize revenues for the grower

and make the system profitable. The selected plant in-row spacing should be dense

enough to ensure high yields without decreasing fruit quality and nutritional value. This

experiment was performed to determine the effect of cultivar and plant in-row spacing on

raspberry yield components and fruit quality in an annual winter production system under

plastic tunnels in a subtropical climate.

Materials and Methods

Plant Material

Dormant bare-root canes (120 to 150 cm long) of 'Tulameen' and 'Heritage' were

purchased in Nov. 2001 from a commercial nursery in the Northwest United States.

Canes were grouped in sets of 50 and their roots were covered with wet cypress sawdust









and wrapped with clear plastic. Each group of canes was placed in a darkened walk-in

cooler at 40 C for 1200 hours. Canes were not watered during chilling.

'Tulameen' is a summer-bearing genotype released in the late 1980's by the

Agriculture Canada Research Station in British Columbia. It is a large fruited, high

yielding cultivar with a late ripening season in the Northern US and South Canada

(Daubeny and Anderson, 1991). 'Heritage' is a fall bearing genotype released in the late

1960's from Cornell University and is the most widely planted red raspberry cultivar in

the world (Daubeny et al., 1992). The success of 'Heritage' may rely on its fruit firmness

and shelf-life, as well as its relatively low chilling requirement and heat tolerance

(Daubeny et al., 1992).

Planting System.

On December 28th 2004, canes were moved out of the cooler and planted in the

beds inside a polyethylene tunnel at the University of Florida at Gainesville, FL (29.69N

and 82.35W). The tunnel was a Quonset style (26.8 m long x 3.6 m wide x 3.3 m high)

covered with 0.15 mm thick ultraviolet resistant polyethylene film. Minimum

temperature inside the tunnel was maintained above 10 C by placing electrical heaters

(Dayton; 6.1 to 17.1 BtuH; model 3UG73) in the central aisle. Ventilation was provided

by raising the polyethylene film to a height of 2.0 m on both sides of the tunnel. There

were two beds inside the tunnel; each bed (26 m long, 60 cm wide and 20 cm depth) was

filled with a mixture of perlite:vermiculite:peat (1:1:1). Temperature was registered daily

every five minutes with a HOBO ProSeries (H08-030-08. Bourne, MA. USA). The

HOBO was placed 1.5 m above the soil and directly underneath a rain shield (11 cm

diameter).









Canes were centered in their respective beds, resulting in 180 cm distance between

rows. Two in-row distances, 25 and 50 cm, were tested. The trellis system consisted of

two wires along the bed at 60 and 170 cm above soil level. Wires were tied to a wooden

post at each end and canes were tied to the wires with flagging tape. A drip irrigation

system consisting of polyethylene lines and microtubes was installed along the center of

each bed. There was one microtube per cane connected to the line with a spot spitter

(Roberts irrigation, San Marcos, CA. USA) delivering 340 mL water per minute.

Plant Growth.

Canes were irrigated daily with 3.4 L of water from 9:00 to 9:10 EST (13:00 to

13:10 GMT) and fertilized every week with 20-8.8-16.6 water soluble fertilizer (J.R.

Peters, Inc. Allentown, Penn.) at a rate of 0.6 g of nitrogen (N) per plant.

Throughout the fruiting season (mid-February to mid-May 2002), all primocanes

were pruned to the soil level once they reached 20 to 25 cm long. Fungicide sprays

started one month after planting, before vegetative budbreak was evident. Captan 50WP

(5.6 Kg/Ha) was sprayed for control of Botrytis every 7 to 10 days throughout winter and

spring.

Flowering began -40 (Heritage) or -50 (Tulameen) days after planting (DAP) and

flowers were counted on all plants. Fruit harvest began -75 (Heritage) and -87

(Tulameen) DAP, and fruit were weighed at each harvest. Fruits were considered ripe and

ready for harvest when they were fully red. At this time, a soft pull was sufficient for

separating the fruit from the core. The peak of fruiting was estimated as one month after

the peak of flowering and fruits harvested during this time were used for chemical

analysis after weighing.









Fruit Chemical Analysis.

Fruits were hand squashed and filtered through three layers of cheesecloth. Juice

was centrifuged for 20 minutes at 2000X g. The supernatant was decanted and used for

soluble solids content (SSC) and total titratable acidity (TTA) measurements. Fruit

soluble solid were determined with a refractometer (Atago PR-101. Tokyo, Japan). Total

titratable acidity was determined as percent of citric acid by diluting six mL of the

supernatant with 50 mL distilled water and titrating with 0.1 N NaOH to a final pH of

8.2. Milliliters of NaOH were recorded and titratable acidity (as citric acid equivalents)

was calculated by the formula given by Garner et al. (2003):

% citric acid = [(mL NaOH) x (0.1) x (0.064) x (100)]/ 6.

The millequivalent factor of 0.064 was used for citric acid.

Experimental Design

A 2x2 factorial was used in this experiment, with two cultivars ('Heritage' and

'Tulameen') and two in-row spacings (25 and 50 cm) as the factors. The resulting four

treatments were arranged in a randomized complete block design with seven replications.

Each replication was comprised of five plants and data were taken only from the three

middle plants. These three plants together were considered an experimental unit. Data

were analyzed using SAS (SAS institute Inc., Cary, NC USA. 2002).

Results

There were no interactions between cultivar and in-row spacing on variables other

than bloom period length; therefore, only main effects will be presented and discussed.

The cool winter temperatures inside the tunnel (Fig. B-1) were favorable for

incidence of diseases like cane Botrytis (Botrytis cinerea Pers.:Fr.) and Phytophthora

root rot (Phytophthora spp.). The application of fungicides on a regular basis after the









observation of symptoms was essential to avoid disease progression and visible fruit

infections. There were fourteen frosts (temperatures below 0 C) in this area during the

2001-02 winter and the electric heaters were able to maintain the tunnel temperature

above 5 C during these freezing events.

Flowering

Flowering began significantly earlier in 'Heritage' than in 'Tulameen' (Fig. 3-1A

and Table 3-1). When flower counts began 43 DAP, 'Heritage' already had an average of

10 flowers per cane; however, 'Tulameen' did not begin to flower until 50 DAP. The

difference in the beginning of flowering resulted in a longer flowering period for

'Heritage' compared with 'Tulameen' (Table 3-1). There was no difference in the time to

50% flowering in either cultivar, which occurred in mid-March (-78 DAP) (Fig. 3-1A).

In-row spacing did not affect the beginning of flowering, but plants spaced at 25

cm in-row reached 50% flowering significantly earlier than plants spaced at 50 cm (Table

3-1), and plants spaced 25 cm in-row had a shorter flowering period than plants spaced at

50 cm in-row. The pattern of flowering at both distances was similar and a peak of

flowering was evident at -78 DAP (Fig. 3-1B).

Fruiting

Fruiting followed a similar pattern as flowering, and fruit harvest began 12 days

earlier in 'Heritage' than in "Tulameen' (Fig. 3-2A and Table 3-2). Additionally, fruit

harvest ended 3 days later in 'Heritage' than in 'Tulameen' (Table 3-2), resulting in a 15-

day longer fruit harvest period for 'Heritage'. The fruit development period, estimated as

the time from 50% flowering to 50% fruit harvest was significantly shorter in 'Tulameen'

compared with 'Heritage' (30 and 35 days respectively) (Table 3-2).









In-row distances did not affect the beginning of fruit harvest, and canes of both

cultivars began fruiting about 80 DAP (i.e. 34 days after the beginning of bloom) (Figure

3-2B and Table 3-2). In-row spacing did not affect the fruit development period;

however, 50% fruit harvest occurred later on canes spaced at 50 cm compared with canes

spaced at 25 cm (Table 3-2). This resulted in a longer fruit harvest period for canes at the

50 compared to the 25 cm in-row spacing. Fruit harvest was concentrated between 102

and 129 DAP for canes at both in-row spacings (Figure 3-2B).

Yield Components

There was no statistical difference between cultivars in flower number per cane,

which averaged 106 and 115 in 'Heritage' and 'Tulameen', respectively (Table 3-3).

Both cultivars had similar fruit set percentages, thus there was no significant difference in

fruit number per cane between cultivars. However, 'Tulameen' fruits were 78% larger

than 'Heritage' fruits (3.1 and 1.7 g per fruit, respectively) and this resulted in

'Tulameen' canes yielding about 80% more than 'Heritage' canes (Table 3-3). On a per

hectare basis, yields would average 2600 kg for 'Heritage' and 4900 kg for 'Tulameen'

(Table 3-3).

Canes spaced at 25 cm in-row had significantly fewer flowers than canes spaced at

50 cm (Table 3-3). However, fruit set was not affected by in-row distances, and averaged

-90%. The difference in flowers per cane resulted in more fruits per cane at 50 cm than at

25 cm in-row spacing (118 vs 80 fruits per cane, respectively). Fruit size was not affected

by in-row distances, thus, the difference in fruit number per cane was responsible for the

increased yields in canes spaced at 50 cm (287 g/cane) compared with canes spaced at 25

cm (192 g/cane) (Table 3-3). When the yield per cane is extrapolated to a per hectare

basis, canes spaced at 25 cm yielded more than canes spaced at 50 cm (4300 vs 3200 kg,









respectively) (Table 3-3). The maximum estimated yield per area obtained in the present

experiment is compared with previously reported yields for the cultivars studied in Table

A-1.

Fruit Quality

Two sampling times were chosen for fruit quality analysis; the first at peak fruiting

and the second 7 days later (April 9 and 16,2004). 'Heritage' fruit titratable acidity was

significantly greater than 'Tulameen' fruits at both sampling times, averaging 1.1% for

'Heritage' and 0.8% for 'Tulameen' (Table 3-4). There were no consistent differences in

fruit SSC between the two cultivars. However, SSC were significantly lower in fruits

from 25 cm than in fruits from 50 cm at both sampling times (13.64 vs 14.21 %,

respectively, on April 9 and 12.60 vsl3.17 %, respectively, on April 16). 'Tulameen' had

higher SSC/TTA ratios than 'Heritage' but in-row spacings had no consistent effect on

this ratio.

Discussion

Cultivars

The earlier bloom and fruiting periods observed in 'Heritage' compared with

'Tulameen' may reflect genotypic differences between fall bearing and summer bearing

raspberry. In general, fall bearing cultivars require less chilling and exhibit earlier

flowering than summer bearing cultivars (Dale et al., 2005) The earlier bloom in

'Heritage' resulted in an earlier fruit harvest period compared with 'Tulameen'.

The longer fruit harvest season in 'Heritage' compared to 'Tulameen' was also

observed in previous work (Daubeny and Anderson, 1991; Keep, 1988) and likely

reflects genotypic differences. Thus, even though the present experiment relied on









floricane production in both 'Heritage' and 'Tulameen', the cultivar difference in fruit

harvest period were still evident.

Although fruit weight in 'Tulameen' was almost twice that in 'Heritage', fruit fresh

weight of both cultivars appears to be lower in our experiment compared with other

work. Fruit fresh weight for 'Tulameen' ranged from 2.9 g/fruit in North Italy (Giongo et

al., 2004) to 5.4 g/fruit in Canada (Daubeny and Anderson, 1991). Fruit weight in

'Heritage' averaged 1.9 g/fruit in the Northeastern U.S. (Hoover at al., 1988) and 1.9 to

2.8 g/fruit in the Southeastern U.S. (Myers, 1993); i.e. at least 1.0 g greater than fruits in

the present experiment (1.7 g/fruit).

The higher yield on 'Tulameen' compared with 'Heritage' canes was the result of

differences in fruit size rather than fruit number per cane. However, even though

'Tulameen' yielded better than 'Heritage' in this experiment, both cultivars remained

below the yield reported for them in other experiments. In previous work, 'Tulameen'

averaged about 185 fruits and 1.0 kg per cane (Daubeny and Anderson, 1991), which is

almost twice the number of fruits and more than three times the yield per cane obtained in

our experiment. Containerized 'Heritage' canes averaged -110 fruit per cane and 2.5 g

per fruit, for a total yield of 280 g per cane (Dale et al. 2001). In this experiment,

'Heritage' yielded 106 fruits per cane for a total yield of 170 g per cane. This decreased

yield per cane compared with previously reported data for these cultivars may be the

result of carbohydrate depletion in the canes after the severe root pruning they received

prior to being shipped from the nursery. Previous experiments in apple (Schupp and

Ferree, 1987; 1989), grape (Ferree et al., 1999; Lee and Kang, 1997) and sweet cherry

(Webster et al., 1997) found a negative impact of root pruning on fruit size. Furthermore,









root carbohydrates in raspberry support early floricane growth (Whitney, 1982;

Fernandez and Pritts, 1994). In raspberry, flower differentiation is still occurring in basal

buds on the cane during budbreak (Williams, 1960: Huang and Lei, 1998) and

carbohydrates are crucial for flower formation in Sinapsis alba (Bodson and Outlaw,

1985), blueberry (Darnell, 1991) and persimmon (Ooshiro and Anma 1998). The

elimination of part of the root for shipping dormant long canes might decrease the root

carbohydrate pool and therefore decrease yield in raspberry.

In general, fruit quality in 'Heritage' was lower than fruit quality in 'Tulameen',

although both cultivars yielded fruits with similar or higher quality (as measured by TA

and SSC) than fruits obtained by previous researchers (Daubeny and Anderson, 1991;

Perkins-Veazie and Nonnecke, 1992). The greater acidity and lower SSC in 'Heritage'

fruits compared with 'Tulameen' is supported by Daubeny et al. (1992), who concluded

that 'Heritage' fruit quality was lower than in many summer-bearing cultivars. Both

cultivars however, had SSC values above 8.0, the minimum proposed for raspberry by

Kader (2001). 'Tulameen' fruits approached the 0.8% maximum TA proposed by the

same author; but 'Heritage' fruits surpassed this maximum. Perkins-Veazie and

Nonnecke, (1992) reported that 'Heritage' fruits can reach 10.5% SSC and 1.2 % TA at

the dark-red stage of maturity.

In-row Spacing

The increased bloom period at 50 cm in-row compared with 25 cm in-row spacing

may be due to decreased light competition and therefore increased carbohydrate synthesis

and availability for flowering. This is more likely than competition for water and

nutrients, since watering and fertilization were made on a plant basis instead of an area

basis. Similarly, the decrease in flower number per cane at 25 cm compared to 50 cm in-









row spacing may also be explained by light competition. Jansen (1997) found an increase

in strawberry flower number when plants were spaced at lower densities (33 to 43

plants/m2) compared to higher densities (66 to 87 plants/m2). Similarly, Menzel and

Simpson (1989) found that continuous or intermittent shade in passion fruit during vine

growth reduced flower number. The shading effect may be even more important in plants

like raspberry, where cane yield depends on the amount of available assimilates per node

(Crandall et al., 1974) and the main source of carbohydrates for the developing fruit are

the nearest leaves in the same lateral (Prive et al., 1994; Fernandez and Pritts, 1993). In

the present experiment, the lower flower number in canes spaced at 25 compared with 50

cm in-row may be the result of more intense shading and a resultant decrease in

assimilate availability.

The fruit development period was not affected by in-row spacing, suggesting that

light was not limiting fruit development in our experiment. Temperature was found to be

the environmental factor with the strongest effect on fruit ripening of blackberry

(Jennings 1979) and cloudberry (Kortesharju, 1993), and this may be true in raspberry

also. If so, there would have been no in-row spacing effect on the fruit development

period, since temperatures inside the tunnel were the same for both in-row spacing.

The negative relationship between yield per cane and plant density has been

reported previously. Oliveira et al. (2004) obtained lower yields as cane density increased

from 8 to 32 canes per meter row in the fall-bearing 'Autumn Bliss' red raspberry.

Similarly, yield per cane and cane density were negatively correlated in four summer-

bearing red raspberry cultivars (Sullivan and Evans, 1992).









The decreased cane yield observed at the denser spacing in the present experiment

was due to a decrease in flower number per cane and consequently a decrease in fruit

number per cane, as neither fruit set nor fruit size were affected by in-row spacing. This

differs from previous work in which fruit set decreased as cane density of red raspberry

increased from 6 to 12 canes per hill (Crandall et al., 1974); however, the authors did not

report the effect of cane density on flower number per cane. In our experiment, the

decreased flower number per cane at the 25 vs the 50 cm in-row spacing would have

resulted in less competition for carbohydrates during fruit set and development, resulting

in similar fruit set percentages at the two spacings even though fruit number per cane was

greater at the 50 cm spacing. Despite the lower yields per cane obtained at 25 vs 50 cm

in-row spacing, the closer spacing would increase the number of canes per area and

potentially increase yields per hectare. These results coincide with Myers (1993) who

found an increase in yield per area by decreasing in-row spacing from 100 to 25 cm in

'Heritage' raspberry.

In general, in-row spacing did not negatively affect fruit quality in our experiment,

as fruit soluble solids were above the minimum of 8% and fruit acidities were near the

maximum of 0.8% proposed by Kader (2001) for raspberry. Fruit quality is related to

light interception by the canopy of red raspberry (Palmer et al., 1987). Vanden Heuvel et

al. (2000) found a decrease in fruit soluble solids when red raspberry canes were trellised

in a horizontal system compared to those fruits from canes in a v-trellis system, the latter

allowing more light to reach the fruiting laterals. Even though the authors did not

measure the light penetration into the canopy, they suggested that the effect of the trellis

system on fruit quality might be mediated by the amount of light reaching the fruit. In our









experiment, a decrease in light interception by fruiting laterals and a concomitant

decrease in the availability of assimilates for fruit development may explain the lower

fruit soluble solids in canes spaced at 25 cm compared with canes spaced at 50 cm.

Fruit titratable acidity remained unaffected by cane density in our experiment.

Similarly, Vanden Heuvel et al. (2000) found no effect of trellising on titratable acidity,

suggesting no effect of light interception on fruit acidity.

Conclusion

This experiment demonstrated that an annual winter raspberry production system in

subtropical climates is feasible; however, the economics of this system need to be

analyzed. 'Tulameen' had higher yields and better overall fruit quality than 'Heritage'.

These characteristics in 'Tulameen', added to its shorter fruit harvest period, makes this

cultivar more suited for this cropping system. Additionally, higher yields can be achieved

by increasing the plant density in the tunnel without affecting fruit quality.

The yield obtained in this experiment was lower than those reported previously for

these cultivars (Daubeny and Anderson, 1991; Myers, 1993; Dale et al. 2001).

Optimizing plant performance in this system will be crucial for if it is economically

viable. Bumble bees should be used in order to improve pollination (Schloemann, 2001)

as 90-95% of pollination in raspberry results from bee activity (Galletta and Violette,

1989). Additionally, more research is needed on irrigation and fertilization, as well as

pest and disease control in this new system.

The relative yield decrease in both cultivars observed in this experiment may be

due to root loss and consequently loss of root stored carbohydrates when canes were

removed from the nursery. This type of root pruning is inevitable in an annual system












such as this one, and further research is needed to determine its possible effects in source-


sink relations and plant yield.


A





-*-Heritage -- Tulameen


2/9 2/16 2/23 3/2 3/9 3/16 3/23 3/30 4/6
43 50 57 64 71 78 85 92 99
Date
Days After Planting


--25 cm --50 cm


2/9 2/16 2/23 3/2 3/9 3/16 3/23 3/30 4/6
43 50 57 64 71 78 85 92 99
Date
Days After Planting

Figure 3-1. Flowering in 'Heritage' and 'Tulameen' red raspberry planted at in-row
spacings of 25 (A) or 50 cm (B) in a winter production in North Florida
(2002). Arrows show 50% of cumulative flowering. (n=7).












14.00


12.00


10.00


*- Heritage -0- Tulameen


8.00


S 6.00


2/28 3/7 3/14 3/21 3/28 4/4 4/11 4/18 4/25 5/2 5/9 5/16
62 69 76 83 90 97 104 111 118 125 132 139

Date
Days After Planting


14.00


12.00


10.00


8.00


- 25 cm 50 cm


2/28 3/7 3/14 3/21 3/28 4/4 4/11 4/18 4/25 5/2 5/9 5/16
62 69 76 83 90 97 104 111 118 125 132 139


Date
Days After Planting


Figure 3-2. Fruiting in 'Heritage' and 'Tulameen' red raspberry planted at in-row
spacings of 25 (A) or 50 cm (B) in a winter production in North Florida
(2002). Arrows show 50% of cumulative flowering. (n=7)









Table 3-1. Flowering of 'Heritage' and 'Tulameen' red raspberry as affected by in-row
spacings in a winter production system in North Florida. (n=7)

Beginning of 50% bloom End of bloom Bloom period
Factor bloom (DAPz) (DAP) (DAP) (days)
Cultivar
Heritage 43.0' 81.6 100.4 57.4
Tulameen 50.6 81.1 99.9 49.2
P-value <0.0001 0.52 0.31 <0.0001
In-row spacing
25 cm 47.8 80.4 99.3 51.5
50 cm 45.9 82.3 101.0 55.1
P-value 0.12 0.01 0.006 0.007
z DAP= Days after planting
y Means in the same factor are different by t-test at the indicated P-value


Table 3-2. Fruit harvest period in 'Heritage' and 'Tulameen' red as affected by in-row
spacings in a winter production system in North Florida. (n=7)
Beginning 50% End of Fruit Fruiting
of fruiting fruiting fruiting Development Period
Factor (DAPz) (DAP) (DAP) Periody (days) (days)
Cultivar
Heritage 74.9x 116.1 139.4 34.6 64.4
Tulameen 87.1 111.3 135.9 30.1 48.8
P-value <0.0001 0.001 0.0003 0.0006 <0.0001
In-row spacing
25 cm 82.4 112.4 136.4 32.0 54.1
50 cm 79.6 115.0 138.8 32.7 59.1
P-value 0.073 0.06 0.007 0.51 0.01
z Fruit development period was estimated as the time between peak bloom and peak fruit
harvest
y DAP= Days after planting
x Means in the same factor are different by t-test at the indicated P-value










Table 3-3. Reproductive development in 'Heritage' and 'Tulameen' red raspberry as
affected by in-row spacing in a winter production system in North Florida.
(n=7)


Flowers


Fruits


Fruit set


Yield per


Fruit size


Yield per area


Factor per cane per cane (%) cane (g) (g) (kg/ha)
Cultivar
Heritage 105.9z 97.7 91.1 169.5 1.74 2583.62
Tulameen 114.6 100.41 91.4 309.8 3.10 4875.96
P-value 0.46 0.81 0.91 0.0001 <0.0001 <0.0001
In-row spacing
25 cm 91.2 79.63 89.7 192.0 2.39 4267.46
50 cm 129.4 118.5 92.7 287.3 2.45 3192.12
P-value 0.004 0.004 0.23 0.004 0.50 0.01
y Means in the same factor are different by t-test at the indicated P-value

Table 3-4 Fruit quality in 'Heritage' and 'Tulameen' red raspberry as affected by in-row
spacing in a winter production system in North Florida. (n=7)
April 9 April 16
Soluble Citric Soluble Citric
Factor solids acid SSC/TTA solids acid SSC/TTA
(%) (%) (%) (%)


Cultivar
Heritage
Tulameen
P-value


13.78z
14.10
0.20


1.20
0.85
<0.000


11.4
11.6
<0.0001


12.37
13.41
<0.0001


1.08
0.82
<0.0001


In-row spacing
25 cm 13.64 1.05 13.6 12.60 0.99
50 cm 14.21 1.01 14.5 13.17 0.91
P-value 0.06 0.16 0.04 0.007 0.16
Y Means in the same factor are different by t-test at the indicated P-value


11.5
17.8
0.008


13.1
16.2
0.16














CHAPTER 4
EFFECT OF INTENSITY AND TIMING OF GIRDLING ON WINTER RASPBERRY
(Rubus idaeus L.) PRODUCTION

Yield in horticultural crops is a function of number of plants per area, fruit number

per plant and fruit size. Fruit number per plant is a function of flower bud number and

fruit set.

Carbohydrate content influences flower bud initiation and fruit set in many plants.

In Sinapsis alba, sucrose accumulation in the meristem appears essential for floral

induction (Bodson and Outlaw, 1985). A similar effect was found in some cultivars of

rabbiteye blueberry (Vaccinium ashei), where the mobilization of 14C-labeled

carbohydrates from leaves to nodes increased under short day compared with long day

conditions (Darnell, 1991). Short days also increased flower bud initiation compared with

long days. The increase in carbon mobilization to nodes occurred early in the short day

cycle, and may be a requirement for enhanced flower bud initiation in blueberry. Ooshiro

and Anma (1998) found similar results for persimmon, where they reported a high

correlation between leaf soluble sugars and the beginning of flower bud initiation (FBI).

They also found a high correlation between flower number and N content in young wood.

They concluded that carbohydrate content during FBI and leafN content during flower

bud differentiation (FBD) are important factors for the number and quality of flowers in

persimmon. However, even though these experiments, which are intended to explain the

relationship between carbohydrate status in the plant and flower initiation, have found a

correlation between these two factors, the question remains as to whether carbohydrates









are playing a key role in FBI or whether the observed increases are also a response to

some other factor inducing flowering. Spann et al. (2004), working with V. corymbosum

interspecific hybrid (southern highbush blueberry) growing under both inductive (short

day) and non inductive (long day) conditions, found greater FBI under inductive short

day conditions, but there was no correlation between carbohydrate concentration and

FBI. This suggests that carbohydrates do not play a primary role in FBI in blueberry.

Havelange et al. (2000) found a relationship between FBI in S. alba and concurrent shoot

to root movement of carbohydrate and root to shoot movement of cytokinin They

concluded that both carbohydrate and cytokinin movement were essential for FBI in that

species.

The effect of carbohydrate status on fruit set has been documented in Citrus, where

fruit set is strongly decreased by reductions in carbohydrate availability (Iglesias et al.,

2003). In citrus, girdling has been used commercially in order to increase carbohydrate

availability for fruit development and avoid early fruitlet drop (Goren et al., 2004).

Crandall et al. (1974) also found a relationship between increased fruit set and

carbohydrate accumulation in nodes of red raspberry. On the other hand, carbohydrate

concentration was not correlated with fruit set and initial fruit growth in strawberry

(Darnell and Martin, 1988) or with fruit set and yield in cranberry (Roper et al., 1995).

Fruit size is also influenced by carbohydrate availability. In rabbiteye blueberry, the

availability of both stored and current carbohydrates were important for fruit size

(Darnell and Birkhold, 1996). Larger fruits were harvested in the cultivar Bonita than in

the cultivar Climax. Apparently the relative reduction in fruit size in 'Climax', where

flower budbreak precedes vegetative budbreak, was the result of depletion in stored









carbohydrates early in the fruit development period and late current carbohydrate

availability. This was not the case for 'Bonita', where flower budbreak and vegetative

budbreak were concomitant. Similarly, Maust et al. (2000) found an increase in fruit size

when 'Sharpblue' blueberries (V corymbosum hybrid) were grown under CO2

enrichment during the previous fall, relative to plants grown in ambient CO2

concentrations. However, the authors did not observe the same tendency in similarly

grown plants of the cultivar Misty. Either the synthesis of assimilates in plants under CO2

enrichment during the previous fall was not sufficient to increase fruit size in 'Misty' or

the fruit size in this cultivar relies more on current than on stored carbohydrate.

Carbohydrate dynamics in raspberry follow a similar pattern as in other perennial

crops. In raspberry, roots and primocanes are responsible for assimilate storage during

winter (Crandall, 1995); At the beginning of the season, when laterals, new primocanes,

and roots start growing simultaneously, the demand for stored carbohydrates increases

(Femandez and Pritts, 1994). During this stage, there is a continuous decrease in root dry

weight, which stops only when floricane net photosynthetic rate increases and the

floricane lateral leaves become sources. At that point, root dry weight begins to increase

(Femandez and Pritts, 1993;1994). The new primocane dry weight also increases

continuously until mid fruiting, at which point dry weight in primocanes remains stable,

before increasing at the end of the season (Fernandez and Pritts, 1993). During the

winter, root dry weight decrease slightly, probably due to respiration, then decrease more

dramatically at the beginning of the following season (Whitney, 1982; Femandez and

Pritts, 1994).









The importance of root carbohydrates for plant yield in raspberry has not been fully

investigated. In perennial fruit crops, carbon stored in roots during the fall is essential for

yield the following season (Teng et al., 1999). In red raspberry, fruit development and

consequently cane yield rely on current carbohydrates from the nearest photosynthetic

leaves (Fernandez and Pritts, 1993; Prive et. al., 1994); however, root stored

carbohydrates are important for yield the following year when current assimilate

availability is inadequate (Fernandez and Pritts, 1996). The question remains whether

root carbohydrates during budbreak are important for raspberry cane yield. On the other

hand, if we consider that raspberry shoot growth coincides with root growth (Atkinson,

1973), then we also have to consider the question whether cane carbohydrates are

important for root growth.

The present experiment tested the hypothesis that root carbohydrates are mobilized

to the cane during budbreak and are important for current cane fruit yield. The objective

was to assess the effect of time and intensity of floricane girdling on cane fruit yield

components and dry weight distribution.

Materials and Methods

This experiment was conducted in a polyethylene tunnel at the University of

Florida in Gainesville, FL (29.69N and 82.35W). The tunnel, bed system, trellising

system, heating and ventilation were previously described in chapter 3. Substrate in this

experiment was a mixture of perlite: peat: coir: pinebark (48: 12:15:25).

Plant Material

Dormant bare-root long cane raspberry cultivars 'Tulameen' and 'Willamette' were

purchased in fall 2002 from nurseries in the Northwest US. Canes arrived in Gainesville

on 25 Oct. 2002 and were grouped, roots wrapped in wet cypress sawdust as described









previously (Chapter 3), and canes were placed in a darkened walk-in cooler at 70 C.

Canes were planted in the tunnel on 18 Dec. 2002, after 1320 hours of chilling.

Both 'Tulameen' and 'Willamette' are summer bearing cultivars. 'Willamette' has

lower yields than 'Tulameen' due to smaller fruit size, but it has an earlier harvest season

(Pacific Agri-food Research Center [PARC], 2003).

Plant Growth

Canes were planted in the beds at 50 cm in-row distance, with between-row

distance of 180 cm. The trellis system was established as previously described in Chapter

3. In order to attain better control of root media moisture and avoid root rot

(Phytophthora spp.), the drip irrigation system was not used during this experiment;

instead, canes were hand-watered as needed at a rate of 2 L per cane. Plants were

fertilized with 20-8.8-16.6 N:P:K (J.R. Peters, Inc. Allentown, Penn.) in the irrigation

water at a rate of 0.6 g of nitrogen (N) per plant. All but three primocanes were removed

once they reached 20 to 30 cm length. The remaining three primocanes were allowed to

grow during the whole season; thus, all plants contained three primocanes. Pruned

primocanes were dried and dry weights obtained. As in the previous experiment (Chapter

3), Captan 50WP (5.6 kg-ha-1) was sprayed for control of Botrytis every 7 to 10 days

through winter and spring. Flowers and fruits per cane were recorded every other day

from the beginning of bloom and fruit harvest, respectively. Fruits were harvested at pink

color (Perkins-Veazie and Nonnecke, 1992) to avoid drupelets loss by crumbling. Fruits

were weighed and dried at 800 C until constant weight and dry weights were recorded.

Fruits harvested at the peak of harvest, estimated as 30 days after the peak of bloom, were

kept frozen at -21o C until fruit quality analysis. After fruit harvest, plants were divided

into roots, canes, laterals and primocanes and fresh and dry weights were obtained. Fruit









quality analysis was conducted as in the previous experiment (Chapter 3). Daily

temperatures were recorded as explained in Chapter 3.

Girdling

Three intensities of floricane girdling (none, 75%, and 100%) at two dates were

tested on each of the two varieties in this experiment. Complete (100%) girdling was

done at 10 cm above the media level by removing a strip of 3 mm of cortex (epidermis,

cortex and phloem) around the entire circumference of the cane with a sharp knife.

Incomplete (75%) girdling was done in a similar way except that the strip of cortex

removed encircled -75% of the cane circumference. Non-girdled canes were used as the

control. Early girdling was done before bloom (6 Feb. 2003 for both cultivars) and late

girdling was done at the peak of fruit harvest (24 Mar. 2003 for 'Willamette' and 2 Apr.

2003 for 'Tulameen'). Captan 50WP (0.5 g/L) was sprayed on the girdling zone the same

day of girdling.

Experimental Design

Three factors were used in this experiment: variety with two levels ('Willamette'

and 'Tulameen'), girdling intensity with three levels (no girdling, complete [100%]

girdling and incomplete [75%] girdling) and girdling time with two levels (early and

late). The resulting ten treatments were arranged in the tunnel in a completely

randomized design (CRD). There were six replications per treatment and one plant was

considered as the experimental unit.

For statistical analysis, two treatments were discarded (early and late 100% girdling

of 'Willamette'), as these plants died as a result of the treatment. When analyzing data

combining cultivars, the two 100% girdling treatments in 'Tulameen' were also

discarded. Late girdling plants were not analyzed in flowering and fruiting time, as these









treatments were applied after flowering and fruiting began. Analyzing cultivars together

for flowering and fruiting time became a two-way 2x2 factorial with two varieties and

two girdling levels (non-girdled control and early, 75% girdled). Analyzing these same

variables by cultivar became a one-way complete randomized design (CRD) with three

treatments (control, 100% girdling and 75% girdling). Yield components, dry weight

allocation and fruit quality data for 'Tulameen' were analyzed as a two-way 2x2

incomplete factorial (2x2 factorial with a control) with two levels of girdling intensity

and two levels of girdling time plus the non-girdled control. Yield components and dry

weight allocation for 'Willamette' were analyzed as a one-way CRD with three

treatments (non-girdled control, early and late 75% girdling). Finally, analyzing these

same variables for both cultivars together became a two-way 2x3 factorial with two

cultivars and three girdling treatments (non-girdled control, early and late 75% girdling).

Data were analyzed using the General Linear Model Procedure in SAS (SAS institute

Inc., Cary, NC, USA. 2002).

Results

Girdling intensity had a dramatic effect on 'Willamette', where both early and late

100% girdled canes wilted and died during the fruit harvest season. 'Willamette' canes

subjected to 75% girdling and all 'Tulameen' canes grew and fruited without problem

during the season. In order to avoid bias in the inferences, both 100% girdled treatments

in 'Willamette' were removed from data analysis.

Flowering

The effect of girdling time on bloom could not be assessed in this experiment as

late girdling was done 96 days after planting (DAP) in 'Willamette' and 115 DAP in

'Tulameen', 11 and 25 days after peak of bloom respectively (Table 4-1). At the time of









late girdling, more than 50% ('Willamette') and 80% ("Tulameen") of the flower buds

had opened in the non-girdled canes.

No difference in bloom period was observed between 'Willamette' and

'Tulameen'; however, 'Willamette' started blooming about 10 days earlier than

'Tulameen' (Table 4-1). Girdled canes reached 50% bloom earlier than non-girdled

canes, but there was no effect of girdling on the length of the bloom period.

In general, girdling had little affect on bloom period in 'Tulameen' or in

'Willamette' when analyzed separately (Tables 4-2, 4-3). Bloom period was similar for

both cultivars, except for a delay of 3 to 4 days in end of bloom in 'Tulameen' girdled

plants compared with the control (p=0.02), which resulted in a slightly longer bloom

period for 100% girdled canes (p=0.09).

Fruiting

Fruit harvest began -5 days earlier in 'Willamette' compared with 'Tulameen', but

the fruit harvest period was significantly shorter in 'Tulameen' than in 'Willamette'

(Table 4-4)

Fruit harvest time was not affected by 75% girdling (Table 4-4). When 'Tulameen'

was analyzed separately, fruit harvest of 100% girdled canes was completed about 17

days later than non-girdled canes (p=0.09) (Table 4-5); however, there was no difference

between treatments in the length of the fruit harvest period. Similarly, 'Willamette' was

not affected by girdling except for a decrease in the time to reach 50% of fruit harvest

and a slight decrease in the length of the fruit harvest period (p=0.08) in 100% girdled

canes compared with the non-girdled controls (Table 4-6).









Yield Components

'Tulameen' had more flowers per cane than 'Willamette' (115 vs 89 respectively);

however, 'Willamette' had significantly higher fruit set, resulting in a slightly greater,

although not statistically different, fruit number per cane (Table 4-7). Fruit size was

significantly larger in 'Willamette' compared with 'Tulameen'; this, combined with the

small difference in fruit number in 'Willamette', resulted in higher yields for

'Willamette' compared with 'Tulameen'.

In general, girdling did not affect 'Tulameen' yield components. Girdling intensity

reduced flower number per cane in 100% girdled treatments compared with the non-

girdled controls (Table 4-8). Early girdling decreased fruit number per cane (p=0.08),

resulting in lower yields in early-girdled canes compared with the control (p=0.09).

Girdling had no effect on yield components of 'Willamette' except for a slight

(p=0.07) reduction in flower number in early-girdled canes compared with the control

(Table 4-9).

Dry Weight Allocation

At the end of the season, there was no difference in dry weight partitioning between

cultivars, except for the dry weight accumulated in fruit (Table 4-10). 'Willamette'

allocated more dry weight to fruits than 'Tulameen' (26.1 vs 13.7 g respectively) during

the growing season; however, this difference did not affect the final total plant dry

weight. Similarly, girdling time had no effect on dry weight allocation compared to the

control (Table 4-10).

When yield components in 'Tulameen' were analyzed separately from

'Willamette', girdling intensity affected dry weight allocation to roots. Dry weight

accumulation in roots of 100% girdled 'Tulameen' was significantly decreased compared









with non-girdled canes (Table 4-11). Dry weight allocation in 'Tulameen' was not

affected by girdling time. Similarly, girdling did not affect dry weight allocation in

'Willamette', except for a slight reduction in dry weight allocated to laterals in early-

girdled canes compared with late-girdled and non girdled control canes (p=0.09) (Table

4-12).

Fruit Quality

Fruit quality was analyzed only for 'Tulameen' fruits. Incomplete (75%) girdling

increased fruit soluble solids (P=0.07) compared with the non-girdled control and 100%

girdled canes (Table 4-13). Similarly, fruits from late girdled canes had significantly

greater soluble solids compared with fruits from non girdled control canes (13.2 vs 12.2

%, respectively). Girdling before bud break had no effect on fruit soluble solids.

Discussion

Bloom and Fruiting Period

In general, girdling did not affect bloom or fruit harvest period in either cultivar.

The timing of bloom and fruiting in temperate crops like raspberry are governed by

genotype and environmental factors, particularly chilling and heat unit accumulation

(Dale et al., 2001; 2003). Some authors have implied the importance of carbohydrates

and/or hormones for flower induction/initiation (Damell, 1991; Havelange et al., 2000;

Spann et al., 2004). In raspberry, after flower induction conditions have been met in late

summer, FBI begins as a continuous process first observed in apical buds of the cane

(Williams, 1959). This process continues down the cane until budbreak in spring. Early

girdling in the present experiment was done at the beginning of budbreak, in early

February, when inflorescences in at least the upper four-fifths of the cane were already

initiated (Williams, 1959). Thus, girdling at this time would be ineffective in altering









bloom time and consequently the fruit harvest period, which are the endpoints of the

inflorescence formation in raspberry.

Yield Components

Both 'Tulameen' and 'Willamette' fruits were smaller than those reported in

previous papers. 'Tulameen' is a large fruited cultivar with fruits up to 5.4 g (Daubeny

and Anderson, 1991), while 'Willamette' fruit is generally smaller, but larger than was

observed in the present experiment (Washington Red Raspberry Commission [WRRC],

2005). The last winter freeze in the present experiment occurred 12 Feb. 2003 and there

was no wild bee activity until late March when wildflowers appeared. Thus, pollination

efficiency was low and resulted in low fruit set and small crumbly fruits in both cultivars.

In general, neither girdling intensity nor girdling time had dramatic effects on yield

components in either cultivar. Although 100% girdled canes of 'Tulameen' had fewer

flowers per cane than the non-girdled controls, the lack of effect of the incomplete (75%)

girdling indicates that this intensity was insufficient to interrupt root to shoot phloem

communication. These results are similar to previous experiments in sour cherry, where

removal of a strip up to 50% of the trunk circumference had no effect on growth or

productivity (Layne and Flore, 1991).

Early girdling slightly decreased flower number per cane in 'Willamette', but had

no effect in 'Tulameen'. This difference may be due to earlier flowering in 'Willamette'

that made this cultivar more responsive than 'Tulameen' to early girdling. However, even

though the difference in flower number per cane in 'Tulameen' was not statistically

significant, early girdling treatments decreased flowers per cane by 18% compared with

the control. Similarly, when both cultivars were considered together, early girdling

resulted in 23% less flowers than the control. Although most flower bud initiation and









differentiation in raspberry occurs in late-winter, individual flowers in the inflorescence

continue differentiation until the following spring (Williams, 1959). Similarly, Qingwen

and Jinjun (1998) observed continuous inflorescence differentiation in raspberry, with

individual flowers continuing differentiation through late April, right before anthesis.

Although early girdling in the present experiment did not appear to affect the timing of

inflorescence differentiation, it may have affected individual flower differentiation in

inflorescences in the lower portion of the cane, resulting in fewer flowers in the early

girdled canes.

Carbohydrates have been implicated as important factors for FBI in some crops

(Darnell, 1991; Ooshiro and Anma, 1998). Roots appear to be the main source of carbon

for the floricanes and primocanes during budbreak in raspberry (Fernandez and Pritts,

1994), which also coincided with the last flush of FBI in the lower cane (Williams, 1959).

This suggests that the prevention of carbon movement from the root to the floricane

during budbreak could result in a reduction in flower number per cane and ultimately

yield per cane. However, the role of root-borne hormones like cytokinin in FBI must not

be ignored (Havelange et al., 2000). The lack of effect of late girdling on flower number

indicates that either the individual flower formation was completed by early spring or that

once the lateral leaves became sources of assimilates, the root was no longer important

for floricane growth and development.

Both fruit set and fruit size are affected by carbohydrate availability (Crandall et

al., 1974; Darnell and Birkhold, 1996; Maust et al.; 2000) and, in this experiment, fruit

set and size remained unaffected by girdling. This suggests that once the lateral leaves

become sources, the assimilates required for the developing fruit are provided by the









leaves nearest to the fruit in the fruiting lateral (Fernandez and Pritts, 1993; Prive et al.,

1994) and fruit growth apparently does not rely on root carbohydrates (Fernandez and

Pritts, 1996).

Dry Weight Allocation

The effect of girdling on dry weight partitioning in raspberry was minimal, with

only a decrease in root dry weight accumulation in 100% girdled 'Tulameen' canes

observed. Dry weight allocation in this experiment was measured only at the end of the

fruiting season. Previous research indicates that root carbohydrates are mobilized to

floricanes and growing primocanes primarily during budbreak until these structures

become photosynthetically active (Fernandez and Pritts, 1993). Subsequently, roots

become a sink for carbohydrates from floricanes and primocanes during the rest of the

season (Whitney, 1982; Fernandez and Pritts, 1993). In the present experiment, roots of

girdled canes were the only plant organ deprived of current carbohydrates during the

season, and this may explain the decrease in root dry weight. Alternatively, girdling also

affects the balance of growth regulators like IAA above and below the girdle (Dan et al.,

1985). The reduction of translocation of shoot-synthesized auxins to the root may also

play a role in the decrease in root dry weight of girdled canes.

Although girdling intensity decreased only root dry weight accumulation in

'Tulameen', there was a general tendency towards decreased dry weight accumulation in

other plant organs due the girdling. This response, added to the significant reduction in

root dry weight in 100% girdled canes, resulted in less total dry weight gain in girdled

plants compared with control plants at the end of the experiment. This reduction in total

plant growth as a result of girdling might be related to alterations in movement of growth

factors other than carbohydrates, as shoot growth does not rely on root carbohydrates









once budbreak has occurred (Fernandez and Pritts, 1994). Cutting and Lyne (1993) found

that girdled peach trees exhibited reduced shoot growth, and this was correlated with

decreases in cytokinin and gibberellin concentrations in the xylem sap.

Fruit Quality

Increases in fruit soluble solids have been reported in girdled peach (El-Sherbini,

1992; Taylor, 2004), grape (Dhillon and Bindra, 1999; Nikolaou et al., 2003), Clementine

mandarin (Yesiloglu et al., 2000) and apple (Arakawa et al., 1998) compared with non-

girdled controls. In the present experiment, increases in soluble solids were observed in

the 75% girdling but not in the 100% girdling treatments. High fruit-to-leaf ratios can

decrease fruit soluble solids and reduce fruit size (Prange and DeEll, 1997). In the present

experiment, 100% girdled canes had a significantly higher fruit:leaf FW ratio compared

with both the 75% girdled and control canes. Thus, there would be greater competition

for assimilates among fruits in the 100% girdled canes, resulting in a decrease in fruit

soluble solids. Similarly, Onguso et al. (2004) found an increase in peach fruit soluble

solids in partially girdled trees compared with non-girdled controls.

In this experiment, the timing of girdling had a significant effect on fruit soluble

solids, with the highest soluble solids observed in late girdled canes. El-Sherbini (1992)

and Chanana and Beri (2004) found increases in fruit soluble solids by girdling peach

branches from bloom through stages I and II of fruit development; however, they found

no effect if girdling was done during stage III. In our experiment, late girdling was done

when fruits harvested for quality analysis were in stage III of fruit development. This is

the stage when 85% of fruit sugar accumulation and fruit growth occur in raspberry

(Crandall, 1995). Thus, raspberry fruit sugar accumulation may be more sensitive to

girdling during stage III of development than has been found in other fruits.









The effect of girdling can be temporary (Goren et al., 2004) unless the girdled zone

is maintained and blockage of phloem translocation continues, in which case a permanent

effect during the growing season can be achieved (Prive et al., 1994). In the present

experiment, the girdled zone was allowed to grow back, thus allowing phloem

translocation to resume later in the growing season. The lower fruit soluble solids

observed in the early girdling compared with the late girdling might result from the

healing of the ring during early fruit growth and the resumption of assimilate

translocation from the floricane to the root during this time. Girdling at the peak of fruit

harvest, when the most rapid accumulation of carbohydrates into the fruit is occurring

(Fernandez and Pritts, 1993; Darnell and Birkhold, 1996), would prevent carbohydrate

translocation from floricanes to roots and therefore increasing assimilate availability for

fruits.

Fruit soluble solids in this experiment were above the minimum recommended for

raspberry; however, fruit citric acid was about three times higher than the maximum

proposed for this crop (Kader, 2001). In this experiment, the drip irrigation system was

not used as explained in Chapter 3 and plants were hand-watered every other day.

Apparently as a result from the daily change in soil moisture, crumbly fruit were frequent

in this experiment and harvest had to be done at pink or red fruit color and not at dark red

color as explained in Chapter 3. Harvesting fruits at unripe stages in this experiment was

probably the cause for higher citric acid levels found in these fruits compared to those

from Chapter 3.

Conclusion

Girdling alters physiological processes that are influenced by carbohydrate and

hormonal status. The effect of girdling before bloom on flower number per cane suggests









the importance of the root in the late FBI process in the raspberry floricanes. On the other

hand, the lack of a girdling effect on fruit development suggests roots may have only a

minor role in this process. However, it is not clear whether carbohydrates, hormones or

their combination are playing the main role in this girdling effect.

The reduction of final root dry weight and the ineffectiveness of girdling in altering

floricane dry weight accumulation indicates that floricanes are an important source of

carbon for root growth, rather than the other way around.

Primocane growth does not appear to rely on floricanes, but the importance of

primocanes in root and floricane growth needs to be determined.

Table 4-1. Flowering of 'Willamette' and 'Tulameen' red raspberry as affected by 75%
girdling in a winter production system in North Florida (n=6).
Beginning of 50% bloom End of bloom Bloom period
Factor bloom (DAP)z (DAP) (DAP) length (days)
Cultivar
Willamette 55.5y 82.0 140.8 85.3
Tulameen 66.3 90.2 144.8 78.5
P-value <0.0001 0.15 0.29 0.13
Girdlingx
Control 61.5 92.0 142.5 81.0
Girdled 60.3 80.2 143.2 82.8
P-value 0.55 0.04 0.86 0.68
zDAP= Days after planting
YMeans of the same factor within the same column are different by t-test at the indicated
P-value.
x Girdling was done on 6 Feb. 2003 by removing a strip of bark encircling 75% of the
cane circumference at 10cm above the media level.

Table 4-2. Flowering of 'Tulameen' red raspberry as affected by girdling intensity in a
winter production system in North Florida (n=6).
Beginning of 50% bloom End of bloom Bloom period
Girdling intensity bloom (DAP)y (DAP) (DAP) length (days)
Control 67.0x 89.7 143.0b 76.0b
75% girdling 65.7 90.7 146.7a 81.0ab
100% girdling 60.3 91.7 146.3a 86.0a
P-value 0.14 0.96 0.02 0.09
zGirdling was done on 6 Feb. 2003 at 10 cm above media level.
YDAP= Days after planting
xLSMean separation by Tukey at the indicated P-value









Table 4-3. Flowering of 'Willamette' red raspberry as affected by girdling intensity in a
winter production system in North Florida (n=6).
Beginning of 50% bloom End of Bloom period


Girdling intensity bloom (DAP)y (DAP) bloom(Di
Control 56.0x 94.3 142.0
75% girdling 55.0 69.7 139.7
100% girdling 58.7 91.3 120.3
P-value 0.47 0.22 0.16
zGirdling was done on 6 Feb. 2003 at 10 cm above media level.
YDAP= Days after planting
xLSMean separation by Tukey at the indicated P-value


\P) length (days)
86.0
84.7
61.7
0.13


Table 4-4. Fruit harvest of 'Willamette' and 'Tulameen' red raspberry as affected by
girdling in a winter production system in North Florida (n=6).
Beginning of 50% fruit End of fruit Fruit harvest
fruit harvest harvest harvest period
Factor (DAP)z (DAP) (DAP) (days)
Cultivar
Willamette 89.5y 115.8 164.0 74.5
Tulameen 94.4 122.4 155.5 56.1
P-value <0.0001 0.31 0.26 0.02
Girdlingx
Control 94.4 127.2 158.0 83.5
Girdled 94.5 111.1 161.6 67.1
P-value 0.81 0.02 0.62 0.64
ZDAP= Days after planting
YMeans of the same factor within the same column are different by t-test at the indicated
P-value.
xGirdling was done on 6 Feb. 2003 by removing a strip of bark encircling 75% of the
cane circumference at 10cm above the media level.

Table 4-5. Fruit harvest of 'Tulameen' red raspberry as affected by girdling intensity in a
winter production system in North Florida (n=6).
Beginning of 50% of fruit End of fruit Fruit harvest
fruit harvest harvest harvest period length
Girdling intensity (DAP)y (DAP) (DAP) (days)
Control 98.8x 126.4 151.4bx 52.6
75% girdling 100.0 118.5 159.7b 59.7
100% girdling 97.6 117.7 167.7a 70.0
P-value 0.36 0.49 0.09 0.11
zGirdling was done on 6 Feb. 2003 at 10 cm above media level.
YDAP= Days after planting
xLSMean separation by Tukey at the indicated P-value









Table 4-6. Fruit harvest of 'Willamette' red raspberry as affected by girdling intensity in
a winter production system in North Florida (n=6_).
Fruit harvest
Girdling Beginning of fruit 50% of fruit End of fruit period length
intensity harvest (DAP)y harvest (DAP) harvest (DAP) (days)
Control 90.0x 128.0a 164.5a 74.5a
75% girdling 89.0 103.7b 163.5a 74.5a
100% girdling 91.2 104.0b 136.7b 45.5bw
P-value 0.38 0.03 0.10 0.08
ZGirdling was done on 6 Feb. 2003 at 10 cm above media level.
YDAP= Days after planting
xLSMean separation by Tukey at the indicated P-value
w Fruit harvest period at 100% girdling was significantly reduced as a result of cane
mortality in the treatment during the experiment.

Table 4-7. Yield components of 'Willamette' and 'Tulameen' red raspberry as affected
by 75% girdling time in a winter production system in North Florida (n=6).
Flowers Fruits Fruit set Yield/cane Fruit size
Factor per cane per cane (%) (g) (g)
Cultivar
Willamette 88.6z 64.8 72.9 149.2 2.24
Tulameen 115.1 50.2 40.8 92.6 1.81
P-value 0.07 0.18 0.0001 0.03 0.004
Girdling timey
Control 112.9x 65.4 53.2 141.6 2.18
Early 86.7 46.4 60.4 91.2 1.88
Late 106.0 60.6 56.9 129.8 2.02
P-value 0.20 0.23 0.64 0.15 0.13
zMeans of the same factor within the same column are different by t-test at the indicated
P-value.
Y Early girdling done on 6 Feb 2003 at the beginning of bloom; late girdling done at peak
of harvest (22 Mar. 2003 for 'Willamette' and 12 Apr. 2003 for 'Tulameen').
xLSMean separation by Tukey at the indicated P-value









Table 4-8. Yield components for 'Tulameen' red raspberry as affected by girdling time
and intensity in a winter production system in North (n=6).
Flowers Fruits Fruit set Yield/cane Fruit size
Factor per cane per cane (%) (g) (g)
Girdling intensity
Control 106.5ay 39.0 36.6 78.1 2.10
75% girdling 99.2ab 37.1 37.7 67.1 1.75
100% girdling 80.2b 30.5 39.8 55.4 1.80
P-value 0.04 0.15 0.73 0.23 0.71
Girdling timex
Control 106.5 39.0a 36.6 78.1a 2.10
Early 87.3 30.7b 37.2 54.2b 1.74
Late 92.0 36.8ab 40.3 68.3ab 1.80
P-value 0.15 0.08 0.62 0.09 0.62
zGirdling was done on 6 Feb. 2003 at 10 cm above media level.
YLSMean separation by Tukey at the indicated P-value
xEarly girdling done on 6 Feb 2003 at beginning of bloom; late girdling done on 12 Apr
2003 at peak of harvest.

Table 4-9. Yield components of 'Willamette' red raspberry as affected by girdling time in
a winter production system in North Florida (n=6).
Flowers Fruits Fruit set Yield/cane Fruit size
Girdling time per cane per cane (%) (g) (g)
Control 122.8ay 95.2 70.8 210.9 2.25
Early 74.3b 63.5 89.4 132.0 2.10
Late 109.0ab 73.0 68.9 170.0 2.22
P-value 0.07 0.31 0.21 0.26 0.76
zEarly girdling done on 6 Feb 2003 at beginning of bloom; late girdling done on 22
March 2003 at peak of harvest.
YLSMean separation by Tukey at the indicated P-value









Table 4-10. Dry weight partitioning in 'Willamette' and 'Tulameen' red raspberry as
affected by girding time in a winter production system in North Florida (n=6)


Factor Roots Primocane
Cultivar
Willamette 79.3z 191.1
Tulameen 85.0 172.5
P-value 0.48 0.23
Girdling timey
Control 87.6x 188.7
Early 81.9 186.3
Late 76.9 170.4
P-value 0.56 0.57
zMeans of the same factor within the


Dry weight (g)
Floricanes Lateral Fruits


s


21.3
19.6
0.33


12.6
14.6
0.38


26.1
13.7
0.004


Total

330.0
300.2
0.16


19.7 15.9 22.7 330.5
20.2 10.2 16.7 320.6
21.5 14.7 20.3 294.3
0.62 0.11 0.47 0.36
same column are different by t-test at the indicated


P-value.
YEarly girdling done on 6 Feb 2003 at beginning of bloom; late girdling done at peak of
harvest (22 Mar. 2003 for 'Willamette' and 12 Apr. 2003 for 'Tulameen')
xLSMean separation by Tukey at the indicated P-value

Table 4-11. Dry weight partitioning in 'Tulameen' red raspberry as affected by girdling
time and intensity in a winter production system in North Florida (n=6).


Factor
Girdling intensity
Control
75% girdling
100% girdling
P-value
Girdling time
Control
Early
Late


Primocane Roots


181.3y
168.2
139.7
0.11

181.3
141.7
166.2


91.3a
82.4ab
67.0b
0.04

91.3
75.2
73.5


Dry weight (g)
Floricane Laterals


18.3
17.6
21.4
0.75

18.3
20.6
18.3


15.0
14.4
11.1
0.30

15.0
12.3
13.5


Fruits Total


14.4a
13.3a
8.9b
0.06

14.4a
9.1b
13.lab


307.6a
296.5ab
250.1b
0.05

307.6
267.7
280.7


P-value 0.17 0.84 0.90 0.77 0.04 0.45
zGirdling was done on 6 Feb. 2003 at 10 cm above media level.
YLSMean separation by Tukey at the indicated P-value
xEarly girdling done on 6 Feb 2003 at beginning of bloom; late girdling made on 12 Apr
2003 at peak of harvest.









Table 4-12. Dry weight allocation pattern in 'Willamette' red raspberry as affected by
girdling time in a winter production system in North Florida (n=6).
Dry weight (g)
Girdling time Primocane Roots Floricane Laterals Fruits Total
Control 196.1 83.9 25.5 16.8aY 30.9 353.3
Early 208.0 75.8 20.2 7.6b 23.8 335.4
Late 169.1 78.3 23.6 13.3a 23.4 301.1
P-value 0.29 0.86 0.63 0.09 0.61 0.40
zEarly girdling done on 6 Feb. 2003 at beginning of bloom; late girdling done on 22 Mar.
2003 at peak of harvest.
YLSMean separation by Tukey at the indicated P-value

Table 4-13. Fruit quality in 'Tulameen' red raspberry as affected by girdling time and
intensity in a winter production system in North-Florida (n=6).
Soluble solids Citric acid
Factor level pH (%) (%) SSC/TTA
Girdling intensity
Control 3.5 12.2by 2.5 4.8
75% girdling 3.6 12.9a 2.6 4.9
100% girdling 3.6 12.2b 2.4 5.1
P-value 0.72 0.10 0.14 0.67
Girdling timex
Control 3.5 12.2b 2.5ab 4.8
Early 3.6 11.9b 2.4b 4.9
Late 3.6 13.2a 2.6a 5.1
P-value 0.89 0.006 0.10 0.58
zGirdling was done on 6 Feb. 2003 at 10 cm above media level.
YLSMean separation by Tukey at the indicated P-value
xEarly girdling done on 6 Feb 2003 at beginning of bloom; late girdling done at peak of
harvest (22 Mar. 2003 for 'Willamette' and 12 Apr. 2003 for 'Tulameen').














CHAPTER 5
EFFECT OF PRIMOCANE REMOVAL AND FLORICANE GIRDLING ON
'TULAMEEN' RED RASPBERRY (Rubus idaeus L.) YIELD IN A WINTER
PRODUCTION SYSTEM

The continuous generation of vegetative canes (primocanes) during the fruiting

season in raspberry generates a sink for root carbohydrates (Whitney, 1982). For a given

primocane, once the new leaves become photosynthetically competent, this current

photosynthate is mobilized to the apices to support further vegetative growth, and to roots

for storage (Fernandez and Pritts, 1993). It is primarily through carbon mobilization from

the primocanes that the root carbohydrate pool is replenished (Whitney, 1982). Root

carbohydrates play an important role in cane yield the following year, as they will

support fruit growth (Rangelov et al., 1998) especially when current carbohydrate

availability is limited (Fernandez and Pritts, 1996).

Since the root carbohydrate storage pool arises primarily by carbon translocation

from primocanes, photosynthetic biomass of primocanes also impacts future cane yield.

Red raspberry primocane defoliation between 25%, and 75% in early August decreased

cane yield the following year by 26% compared with the non defoliated controls, while

total defoliation resulted in a 55% yield decrease (Raworth and Clements, 1996).

As with early primocane development, floricane development during budbreak and

leaf expansion also depends on root carbohydrates, as inferred by the reduction in root

dry weight during this stage (Whitney, 1982; Fernandez and Pritts, 1994). Once the

floricane leaves reach maturity, they replenish the cane carbohydrate pool and support

growth of apices and developing fruits until the end of the harvest season, at which time









the floricane carbohydrates are depleted and the cane dies (Whitney, 1982; Fernandez

and Pritts, 1993; Prive, 1994).

There appears to be substantial competition for root carbohydrates between

primocanes and floricanes during certain phenological stages. Primocane removal at the

beginning of bloom resulted in yield increases compared with plants where primocanes

were maintained during the fruiting season (Dalman, 1989), suggesting competition for

carbohydrates between primocanes and floricanes. Similar, primocane removal during

the growing season of raspberry cv. Glen Clova increased floricane dry weight and fruit

yield compared with plants in which primocanes were not removed (Wright and Waister,

1982b). Conversely, the number of primocanes in plants with floricanes removed was

significantly greater than in plants with fruiting floricanes (Wright and Waister, 1982a).

In the fall-bearing 'Heritage', plants with all inflorescences removed produced

significantly more primocanes compared with plants in which no inflorescences were

removed (Vasilakakis and Dana, 1978).

Although growth enhancement of primocanes by eliminating floricane

carbohydrate sinks and vice versa could be explained by a competition for light; the plant

carbohydrate status should not be ignored since roots can act as a source for both

floricanes and primocanes during early growth, and as a sink for carbohydrates from

floricanes or primocanes later in the growing season. This is supported by previous work

that found a decrease in both root carbohydrate content (Whitney, 1982) and root dry

weight (Fernandez and Pritts, 1993) during raspberry budbreak. Later in the season;

however, roots become active sinks for carbohydrates from both floricanes and

primocanes (Fernandez and Pritts, 1993).









As the root stored carbohydrates play an important role in flower formation

(Bodson and Outlaw, 1985; Darnell, 1991; Ooshiro and Anma 1998) and yield

(Fernandez and Pritts, 1994), understanding carbohydrate partitioning patterns among

primocanes, floricanes, and roots is crucial for the successful implementation of an

annual winter production system that relies on bare root long-canes, where the root

system has been reduced during removal from the nursery rows. The reduction in root

biomass would be expected to decrease the carbohydrate pool in the root and alter

carbohydrate dynamics of the plant.

The hypothesis of the current experiment is that in an annual winter production

system, primocanes contribute to current floricane fruit yield by providing assimilates to

the root and therefore decreasing root demand for assimilates from the floricane. The

objective was to determine the effect of girdling and primocane removal on floricane

growth and yield components.

Materials and Methods

This experiment was conducted in a polyethylene tunnel at the University of

Florida in Gainesville, FL (29.69N and 82.35W). The tunnel was described in chapter 3.

Both the heating and ventilation systems remained as described in chapter 3.

Plant Material

Bare-root long canes of the red raspberry cultivar Tulameen were purchased from a

commercial nursery in the Northwest U.S. Canes arrived in mid-January 2004, and roots

were wrapped in wet cypress sawdust as described in chapter 3. Canes were placed in a

dark walk-in cooler at 70 C for 1290 hours.

After chilling, canes were individually planted in black polyethylene containers

(OlympianTM C4000. Nursery supplies, Inc. Fairless Hills, PA., U.S.A.) filled with a









mixture of coir, perlite and Canadian peat (1:3:1). Containers were 38 cm high, 40 cm in

diameter and 36.7L capacity. Containerized canes were placed in the tunnel the same day

of planting. Canes were hand-watered as needed with 2L water per pot and fertilized

weekly with 20-8.8-16.6 N:P:K water soluble fertilizer (J.R. Peters, Inc. Allentown,

Penn.) at a rate of 0.6 g of nitrogen (N) per plant.

Leaf diseases were controlled by spraying Captan 50WP every 7 to 10 days at a

rate of 5.6 kg-ha-1. Subdue Maxx was diluted in the irrigation water at a rate of 60 L.L-L1

and applied to the potting media once at the beginning of the growing season to control

Phytophthora root rot. Plants were scouted for two-spotted spider mites and eventually

controlled with a commercial mixture of mite predators (Phytoseiulupersimilis,

Neoseiulus californicus and Mesoseiulus longipes). Bumblebees (Bombus impatients)

were released in the tunnel at the beginning of bloom to improve pollination. Daily

temperatures were recorded as described in Chapter 3.

Girdling and Cane Removal

On 10 May 2004 (62 days after planting), 24 floricanes were selected for

uniformity in height and vigor. Half of the floricanes were girdled by removing a 3-mm

strip of cortex with a sharp knife around the cane at 10 cm above the media level. At the

same time, primocanes were removed in half of each of the girdled and non-girdled

treatment plants. New primocanes in these plants were removed continuously throughout

the experiment. The remaining plants were allowed to grow three primocanes each.

Captan 50WP was sprayed to the girdled zone at a rate of 0.5 g-L-1 the same day of

girdling.









Reproductive Measurements

Flowers and fruits per cane were recorded every other day beginning on 11 May

2004. Fruit were harvested at pink or red color stage (Perkins-Veazie and Nonnecke,

1992). Fruits were weighed and kept frozen at -200 C. After fruit harvest, plants were

divided into roots, canes, laterals and primocanes, fresh weight obtained and plant

segments dried at 800 C until constant weight. Fruits from peak of harvest were analyzed

for quality as explained in Chapter 3. The remaining fruits were dried at 800 C and dry

weight obtained.

Photosynthesis

Net photosynthesis (Pn) was determined by measuring the CO2 assimilation rate in

floricane and primocane leaves with a portable gas exchange analyzer (LiCor LI-6400;

Lincoln NE, USA.) operated as an open system. The uppermost fruiting laterals in the

top, middle, and lower sections of each floricane were selected and Pn was measured on

the fully open distal leaf of each lateral. Data from the three sections in each floricane

were pooled to determine the floricane Pn. In primocanes, the uppermost fully open leaf

was selected and Pn was determined on the distal leaflet. Plants were watered (2 L/pot)

the day before CO2 measurements. Photosynthesis was measured between 9:00 and 11:00

a.m. (2.5 to 4.5 hours after sunrise) every week from the peak of fruiting (2 June, 2004;

85 DAP) through 24 June, 2004 (107 DAP) when 80% of fruits had been harvested.

Experimental Design

A 2x2 factorial was used to study the effect of girdling (girdling vs. no girdling)

and primocane removal (3 vs. 0 primocanes per pot). Treatments were arranged in the

tunnel in a randomized complete block design with cane vigor and diameter used as block

determinants. There were six replications per treatment and one plant (pot) was









considered an experimental unit. All girdled canes without primocanes died 20 days after

girdling and they were not considered for further analysis. Remaining treatments were (1)

non-girdled canes with primocanes (Control), (2) non-girdled canes without primocanes

and (3) girdled canes with primocanes. Data from these three treatments were analyzed as

a complete randomized block design by using the GLM procedure in SAS (SAS institute

Inc., Cary, NC USA. 2002).

Results

Girdled canes without primocanes began dying 20 days after girdling and all plants

in this treatment died during fruit harvest. In order to avoid bias in the inferences, this

treatment was not included in the statistical analysis.

Flower counting began at 63 DAP. At this point, more than 40% of the total

flowers were already opened. Bloom ended -18 day earlier in girdled canes compared

with the non-girdled control canes, but primocane removal in non-girdled canes had no

effect on the end of bloom (Table 5-1). Non-girdled canes had a second flush of flowers

around 90 DAP (Fig 5-1A).

The pattern of fruiting was similar in all treatments (Fig 5-1B). Treatments had no

significant effect on the beginning or the end of fruiting, but fruiting period length was

reduced by 9 days in girdled canes compared with non-girdled canes. Primocane removal

in the non-girdled canes had no effect on fruiting period length (Table 5-1).

There was little effect of treatment on yield components, although yield/cane was

reduced in the girdled + primocane treatment (P< 0.11) compared with the two non-

girdled treatments (Table 5-2). There was also little treatment effect on dry weight

allocation within the plants, except for a reduction in root dry weight in the non-girdled +









no primocane treatment compared with the treatments in which 3 primocanes were

present, regardless of girdling treatment (Table 5-3).

In general, photosynthesis was greater in non-girdled compared with girdled canes,

regardless of the presence of primocanes. However, differences were significant only at

85 and 100 DAP (Table 5-4).

Fruit soluble solids in the non-girdled + primocane removal treatment were

increased slightly compared with the non-girdled + primocane treatment (p=0.09), but

there were no treatment effects on titratable acidity or the soluble solids to titratable

acidity ratio (Table 5-5).

Discussion

The effect of girdling on end of bloom and shortening of the fruit harvest period

may result from a decrease in carbohydrate availability in the girdled floricanes late in the

flowering period. In red raspberry, flower bud initiation occurs basipetally from late

summer through winter and some flowers differentiate in the lower cane after bloom

onset in the spring (Williams, 1959; Qingwen and Jinjun, 1998). Carbohydrates play a

role in flower bud initiation and development in Sinapsis alba L. (Bodson and Outlaw,

1985), Vaccinium ashei Reade (Darnell, 1991) and Diospyros kaki L (Ooshiro and Anma

1998). In red raspberry, the increasing demand for carbohydrates in floricanes during leaf

and flower development is fulfilled first with cane, then with root carbohydrates

(Whitney, 1982; Fernandez and Pritts, 1993). In the present experiment, girdling was

done around peak of bloom (62 DAP), preventing further movement of carbohydrate

from roots to floricanes. This may have resulted in a carbohydrate limitation that

decreased initiation and development of flowers in the lower parts of the floricane and

shortened the bloom and fruiting periods. Although not statistically significant, there was









a 22% decrease in flower number and a 15% decrease in fruit number (p=0.14) in girdled

compared with non girdled canes. Earlier girdling may have had a much more serious

effect on decreasing flower initiation and fruit number, especially in the lower part of the

floricane

Although the decrease in flower and fruit number in girdled floricanes was not

statistically significant compared with the non-girdled floricanes, leaf Pn of girdled

floricanes was reduced compared to Pn of non-girdled canes. This may be a consequence

of reduced sink demand in the girdled canes. Previous studies have shown that low fruit

loads can decrease photosynthesis in girdled branches of citrus (Iglesias et al., 2002),

apple (Zhou and Quebedeaux, 2003) and mango (Urban et al., 2004) compared with

either non-girdled or girdled branches with high fruit loads. Floricanes are also a source

of carbohydrates to roots during the fruiting period (Fernandez and Pritts, 1993). The

decreased sink demand due to the reduction of flowers and fruits in girdled floricanes,

added to the isolation of the root system and therefore elimination of the roots as a sink,

might result in a decrease in floricane photosynthesis. Regardless of the differences in Pn

among treatments in this experiment, Pn for all treatments were similar to previous work

on raspberry in traditional cropping systems (Oliveira et al., 2004)

Although girdling often increases yield and fruit quality in some crops, due

presumably to increased carbohydrate accumulation above the girdle (Allan et al., 1993),

girdling slightly decreased yield in the present experiment. This may be due to a cascade

of effects that girdling exerted on the floricane. First, an initial reduction of root

carbohydrates moving to the floricane, followed by a reduction in flower and fruit

number, which, in turn, decreased net photosynthesis and ultimately assimilates for fruit









development. Others have also reported that girdling had no effect on fruit yield (Iglesias

et al., 2002).

Fruit citric acid in this experiment was about three times the maximum proposed

for raspberry (Kader, 2001). Plants were watered as explained in Chapter 4 and crumbly

fruits were also frequent. In order to avoid fruit loss, harvest was done at pink and red

color stages resulting in higher citric acid content in fruits from this experiment. Fruit

soluble solids, however, remained above the minimum proposed by Kader (2001).

Primocane removal decreased root dry weight but had no effect on floricane dry

weight. Both primocanes and floricanes are sources of assimilates for roots, but there

appears to be no reciprocal translocation of assimilates between primocanes and

floricanes (Fernandez and Pritts, 1993).

Floricanes appear to act as carbohydrate sources for roots in red raspberry under

some conditions, as observed by Fernandez and Pritts (1993). This is supported by the

normal flowering and fruiting that occurred in non-girdled canes without primocanes,

where the only source of carbohydrates to roots would be the floricane. Additionally,

girdled canes without primocanes died within 20 days of girdling, which may have been

due to elimination of floricanes as a carbohydrate source for roots resulting in a severe

carbohydrate limitation in the roots.

Conclusion

Girdling resulted in a significant reduction in the fruiting period and tended to

decrease flower and fruit number per cane. Girdling prevented root carbohydrate

translocation to the floricane during the latter part of the blooming season, and apparently

decreased flower bud initiation/differentiation in the lower portion of the cane. Primocane

removal had little effect on growth and development, other than decreasing root dry






69


weight. Primocanes appear to be the main source of carbon for roots; however, the

carbohydrates allocated to roots from primocanes have no effect on floricane growth,

since primocane removal did not affect dry weight accumulation in floricanes. Floricanes

appear to be a carbohydrate source to roots as well, but in limited amounts, which do not

affect their own growth.









70




400
A

350
--- Non girdled + 3 Primocanes
-1- Non girdled + No Primocanes
300
-- Girdled + 3 Primocanes


250



S200



150 / \
'I '

100 i \' \




0


60 70 80 90 100 110 120 130
Days after planting


50
B
45
I'
I'
40 I
S-e-- Non girdled + 3 primocanes
35 -9 ---I Non Girdled + No Primocanes
S- Girdled + 3 Primocanes
30









I /


/ I
5 /
20 -











0 -
60 70 80 90 100 110 120 130
Days after planting



Figure 5-1. Effect of girdling and primocane removal on bloom (A) and fruiting (B) in

'Tulameen' red raspberry in a winter production system. Arrows indicate the

girdling time (62 days after planting) (n=6).









Table 5-1. Effect of girdling and primocane removal on bloom and fruiting in 'Tulameen'
red raspberry in a winter production system (n=6).
End of Beginning End of Fruiting
bloom of fruiting fruiting period length
Treatment (DAP)z (DAP) (DAP) (days)
Non-girdled + 3 primocanes 109.5ay 71.7 114.7 43.0a
Non-girdled + no primocanes 109.5a 74.7 118.0 43.3a
Girdled + 3 primocanes 91.0b 74.1 108.5 34.3b
P-value 0.002 0.76 0.17 0.08
z DAP= Days after planting
YLSMean separation by Tukey at the indicated P-value


Table 5-2. Effect of girdling and primocane removal on yield components of 'Tulameen'
red raspberry in a winter production system (n=6).
Flowers Fruits Fruit set Yield per Fruit
Treatment per cane per cane (%) cane (g) size (g)
Non girdled + 3 primocanes 180.0 60.0 36.8 160.4 2.65
Non girdled + no primocanes 164.8 64.5 43.1 145.6 2.27
Girdled + 3 primocanes 139.8 50.8 38.3 116.9 2.31
P-value 0.58 0.14 0.77 0.11 0.16


Table 5-3. Effect of girdling and primocane removal on dry weight allocation in
'Tulameen' red raspberry in a winter production system (n=6)


Treatment
Non -girdled + 3 primocanes
Non-girdled + no primocanes
Girdled + 3 primocanes


Dry weight (g)
Roots Floricane Primocanes Laterals


32.9ay
26.4b
35.2a


29.8
30.7
32.1


35.4
ND
39.1


P-value 0.005 0.35 0.1
z Primocanes are not included
YLSMean separation by Tukey at the indicated P-value


32.5
29.2
27.5
0.54


Fruits
24.1a
24.6a
17.8b
0.10


Totalz
119.4
111.0
112.5
0.57


Table 5-4. Effect of girdling and primocane removal on leaf photosynthesis (imol
C02'm-2.S-1) of 'Tulameen' red raspberry in a winter production system (n=6)
Day after planting
Treatment 85 92 100 107
Non-girdled + 3 primocanes 11.03az 8.45 8.78ab 5.62
Non-girdled, no primocanes 11.75a 7.47 9.35a 4.87
Girdled + 3 primocanes 8.77b 6.93 7.05b 3.75
P-value 0.011 0.125 0.054 0.336
zLSMean separation by Tukey at the indicated P-value


15






72



Table 5-5. Effect of girdling and primocane removal in 'Tulameen' raspberry fruit quality
in a winter production system (n=6).
Soluble Solids TA SSC/TTA
Treatment (%) (% of Citric acid) ratio
Non Girded + 3 primocanes 11.15b 2.33 4.87
Non girdled + 0 primocanes 12.08a 2.34 5.24
Girdled + 3 primocanes 11.85ab 2.52 4.77
P-value 0.091 0.348 0.331














CHAPTER 6
ROOT PRUNING EFFECTS ON GROWTH AND YIELD OF RED RASPBERRY
(Rubus idaeus L.)

There is increasing interest in off-season production of raspberry, necessitating the

need for new cropping systems. In south Florida, an annual production system has been

examined, in which pre-chilled long cane raspberry cultivars are purchased from northern

nurseries and field-planted in late January. Fruit harvest occurs as early as March (Knight

et al., 1996). In this annual system, raspberry plants are removed after harvest and

replaced with new pre-chilled long canes for the next season. The disturbance of the root

system during digging and shipment from the nursery leads to significant root loss and

may alter the root-shoot balance in such a way that results in yield decreases.

Many studies have shown that root pruning in temperate crops affects shoot growth

and yield. Dormant root pruning reduced vegetative growth and fruit size in apple

(Schupp and Ferree, 1987; 1989), grape (Ferree et al., 1999; Lee and Kang, 1997) and

sweet cherry (Webster at al., 1997). However, root pruning during bloom had no effect in

apple (Elfving et al., 1991) or apricot (Arzani et al., 1999). The different effects of root

pruning may be due to differences in root carbohydrate mobilization to the shoot.

Dormant pruning would remove a large source of reserve carbohydrate that would

normally be used to support vegetative and/or floral budbreak. However, delaying root

pruning until bloom would allow translocation of root carbohydrates prior to the root

pruning treatment, thus the carbohydrate supply to support budbreak would not be

limited.









In raspberry, spring vegetative and reproductive growth are concomitant (Atkinson,

1973) and both need carbohydrate for production of new biomass. Primocanes also begin

growth at this time and are an additional sink for root carbohydrates (Whitney, 1982).

Root pruning could further exacerbate carbohydrate competition since root growth also

increases after root pruning (Schupp et al., 1992), resulting in additional sink activity.

Given this scenario and the low photosynthetic activity in floricane leaves before bloom

(Fernandez and Pritts, 1994), there is a high probability that roots of raspberry plants,

especially in an annual production system, may be carbohydrate depleted by the

beginning of bloom.

Root carbohydrate depletion would affect not only spring shoot growth and early

flower/fruit set, but could also affect flower bud initiation/differentiation in raspberry.

Flower bud initiation/differentiation in the lower portion of raspberry floricanes continues

during early bloom (Williams, 1959; Qingwen and Jinjun, 1998) and adequate

carbohydrate supply is critical for this process (Bodson and Outlaw, 1985; Darnell, 1991;

Ooshiro and Anma, 1998). Therefore, the elimination of part of the root system during

dormancy could decrease the carbohydrate reserves required for early floricane lateral

growth, including flower bud initiation. Consequently, fruit number and yield would

decrease.

Additionally, root pruning may also affect cane yield by decreasing fruit size.

Fernandez and Pritts (1996) found that the maximum demand for assimilates in red

raspberry is at the onset of fruiting while primocanes, roots, and fruits are all growing. In

an annual cropping system, the elimination of part of the root system and the consequent









intensive root regeneration (Schupp et al., 1992) during the high sink activity of the

raspberry plant could decrease carbohydrate availability for the developing fruit.

The hypothesis in the present experiment was that root pruning decreases cane

carbohydrates in red raspberry during budbreak and early bloom, resulting in a decrease

in yield. The objectives were to assess the effect of root pruning on yield and plant

carbohydrate allocation.

Materials and Methods

The experiment was conducted at the University of Florida in Gainesville, Florida.

(29.69N and 82.35W). The tunnel, trellising system, heating and ventilation were

described in Chapter 3. The substrate and potting system were as described in Chapter 5.

Plant Material

Bare-root long canes of the summer bearing red raspberry cultivar Cascade Delight

were purchased from a commercial nursery in the Northwest U.S. Canes arrived in mid-

January 2004, and roots were wrapped in wet cypress sawdust as in previous years. Canes

were placed in a dark walk-in cooler at 70 C for 1320 hours

On 11 Mar. 2004, canes were potted in 36.7 L black polyethylene containers as

described in Chapter 5 and placed outdoors. Plants were hand-watered with 2L water per

pot three times a week and fertilized with a water soluble fertilizer (20N-8.8P-16.6K; J.R.

Peters, Inc. Allentown, Penn.) at a rate of 0.6 g of nitrogen per plant. Phytophthora root

rot, leaf fungal diseases and two-spotted spider mite control were achieved by using

Captan 50 WP, Subdue maxx, and a commercial mixture of mite predators, respectively,

as indicated in Chapter 5.









Canes were allowed to fruit during the season, and fruits were harvested when ripe.

All primocanes in the container were allowed to grow throughout the season and only

floricanes were pruned at the media level after fruit harvest.

In Dec. 2004, 24 plants were selected for the experiment. Two primocanes per plant

were selected based on uniform height and vigor and the rest were pruned at the media

level. Half of the plants were root pruned in early December. Root pruning was

performed with a sharp machete and roots were pruned to a 12x12x12 cm3 volume,

removing approximately 45% of the root dry weight. After root pruning, four root-

pruned and four non root-pruned plants were separated into roots, canes, and leaves and

fresh weights measured. Plant tissues were dried at 800 C until constant weight and dry

weights were recorded. The remaining plants were placed in a dark walk-in cooler on 13

Dec. The cooler temperature was 100 C for 240 hours, then decreased to 70 C for an

additional 980 hours. On 31 Jan. 2005, chilled canes were moved to the tunnel and

auxiliary heating and ventilation was done as described in Chapter 3. Plant watering,

fertilizing, and pest control in the tunnel was performed as explained above.

At budbreak in early March, four root-pruned and four non root-pruned plants were

harvested and processed as described above. The remaining plants were allowed to grow

and fruit. Three new primocanes were allowed to grow per plant. Bumble bees (Bombus

impatients) were released at the beginning of bloom in early April to improve pollination.

Flowers and fruits were counted and fruits were hand-harvested at pink and red color

stages, weighed and either dried at 800 C until constant weight or kept frozen at -210 C

for fruit quality analysis as explained in Chapter 3. Each plant was harvested individually

at the end of fruit harvest. Plants were divided and processed as described above.









Photosynthesis

Net photosynthesis (Pn) was determined by measuring the CO2 assimilation rate in

floricane and primocane leaves with a portable gas exchange analyzer (LiCor LI-6200;

Lincoln NE, USA.) operated as an open system. Photosynthesis was measured between

10:00 and 12:00 a.m. (3 to 5 hours after sunrise) at beginning of bloom (5 Apr. 2005; 64

days after planting (DAP)) and at the peak of fruit harvest (13 May; 102 DAP). The

uppermost fruiting laterals in the top section of each floricane were selected.

Photosynthesis was measured on the distal leaflet of the most distal fully open leaf of

each lateral. In primocanes, the uppermost fully open leaf was selected and Pn was

determined on the distal leaflet. Plants were watered (2 L/pot) the day before CO2

measurements were taken.

Carbohydrate Analysis

Soluble sugars and starch in roots, floricanes lateralss, cane, and fruits), and

primocanes (when present) were measured. Dried tissue was ground and passed through a

20 mesh screen (1.27 mm mesh). Soluble sugars were determined by extracting 50 mg of

ground tissue in 2 mL 80% ethanol (1:100 w/v). Tissue was shaken for 20 minutes at 150

rpm on an orbital shaker (Fisher Scientific Model 361; U.S.A.). Extracts were centrifuged

at 2,270 x g for 10 minutes. After decanting the supernatant, the remaining pellet was re-

extracted twice in 1 mL 80% ethanol (1:100 w/v). Supernatants were combined, final

volume measured and aliquots used for total sugar analysis. Pigment was removed by

mixing 35 mg activated charcoal and centrifuging at 14,900 x g for 4 minutes. Percentage

recovery was estimated by using 14C-sucrose as an external standard. Soluble sugars

were determined by the phenol-sulfuric acid colorimetric procedure (Chaplin and

Kennedy, 1994) using glucose as a standard and correcting for percent recovery.









Tissue starch content was determined by suspending the insoluble pellet in 2.0 mL

0.2N KOH and boiling for 30 min. The pellet was cooled and adjusted to a pH of 4.5 with

1.0 mL 1M acetic acid. Rhizopus amyloglucosidase (50 units) and a-amylase (10 units)

(Sigma Chemical Co., St. Louis Mo., U.S.A.) in 0.2M calcium acetate buffer (pH 4.5)

were added to each sample. After enzyme addition, samples were incubated at 370 C for

24 hours while shaking at 78 rpm in a constant temperature bath (Magni Whirl. Blue M.

Blue Island, IL. U.S.). After incubation, samples were centrifuged at 2, 270 x g for 10

minutes and the supernatant decanted, measured, and aliquots used for sugar analysis.

Supernatant pigment was removed by mixing 35 mg activated charcoal and centrifuging

at 14,900 x g for 4 minutes. Percentage recovery was estimated by using 14C-sucrose as

an external standard. Glucose obtained from starch hydrolysis was quantified by the

phenol-sulfuric acid method (Chaplin and Kennedy, 1994) using glucose as standard and

correcting for percent recovery.

Experimental Design

The two root treatments and three plant harvest dates were analyzed as a 2x3

factorial for carbohydrate content and dry weight allocation. Treatments were distributed

in the tunnel as a randomized complete block design. There were four replications per

treatment with single-plant experimental units. Yield components, photosynthesis, and

fruit quality were analyzed as one-way randomized complete block design. Data were

analyzed with the GLM procedure of SAS (SAS Inst. Inc., Cary, N.C.).

Results

There were no significant interactions between root pruning and time of plant

harvest on any variable; thus, only main effects are presented. Root pruning significantly

decreased dry weight partitioning to fruit compared with no root pruning (Table 6-1).









Root dry weight also decreased as a result of root pruning; however, there were no effects

of root pruning on floricane, lateral shoot, or primocane dry weight.

Dry weight of all organs except floricanes increased as the season progressed

(Table 6-1), resulting in a significant increase in total plant dry weight at the end of the

growing season.

Root pruning decreased the number of flowers per cane compared with the non

root-pruned canes (Table 6-2). This decrease resulted in significantly less fruits per cane

and consequently lower yields per cane in the root-pruned canes. Fruit size was not

affected by root pruning (Table 6-2).

Fruit quality was generally unaffected by root pruning except for a slight decrease

in soluble solids in root-pruned compared with non root-pruned plants (p=0.06),

However, the decrease in fruit soluble solids resulted in a significant decrease in the

soluble solids to acidity ratio (Table 6-3). Regardless of the treatments, fruit soluble solid

remained above the minimum proposed for raspberry (Kader, 2001). Fruit citric acid,

however, was three times the maximum proposed for this crop, resulting from the non

fully ripe stages of harvest as explained in Chapters 4 and 5.

Net photosynthesis in this experiment was similar to previous work on raspberry in

traditional cropping systems (Oliveira et al, 2004). However, in this experiment, Pn was

significantly lower in floricane leaves of root-pruned canes compared with floricane

leaves of non root-pruned canes at the beginning of bloom (64 DAP). There were no

differences in leaf Pn at the peak of fruit harvest (102 DAP)(Table 6-4). Primocane leaf

Pn was measured only at peak of harvest and was not affected by root pruning.









Root pruning did not affect soluble sugar or starch concentration in any organ or in

the whole plant (Tables 6-5 and 6-6). However, total carbohydrate concentration (soluble

sugars + starch) was significantly lower in roots of root-pruned plants compared with non

root-pruned plants (Table 6-5). On the other hand, total carbohydrate concentration in

primocanes of root-pruned plants was significantly higher than primocanes of non root-

pruned plants (Table 6-5).

Soluble sugar concentration decreased in roots and laterals between the time of root

pruning (mid-Dec.) and budbreak (mid-March) (Table 6-5). Root soluble sugar

concentrations then increased between budbreak and fruit harvest, at which time they

were similar to concentrations at the time of root pruning. Soluble sugar concentrations in

laterals continued to decrease through the end of fruiting. On a whole plant basis, soluble

sugar concentration was significantly lower at budbreak compared with the other harvest

times (Table 6-6).

Root starch concentration was lowest at budbreak and increased significantly by the

end of fruit harvest (Table 6-5). Similarly, starch concentration in both laterals and

primocanes was lower at budbreak than at the end of fruit harvest (Table 6-5). On a

whole plant basis, starch concentration was significantly lower at budbreak compared to

the other harvest times (Table 6-6).

Total carbohydrate concentration (soluble sugars + starch) in all organs decreased

at budbreak, but this was significant only in roots (Table 6-5). However, on a whole plant

basis, total carbohydrate concentration was significantly lower at budbreak than at the

other harvests (Table 6-6).









Discussion

The decrease in root dry weight after root pruning was expected, since

approximately 45% of the total root dry weight was removed at pruning. However, the

lack of interaction between root pruning and harvest time on root dry weight indicates

that root growth occurred at the same rate in both root and non root-pruned plants. The

lack of significant effect of root pruning on dry weight allocation to plant structures other

than roots and fruits suggests that raspberry shoot growth may be relatively independent

from the root carbohydrate supply in this production system. In the present experiment;

however, root pruning decreased floricane lateral dry weight by -50% compared with

lateral dry weight of non root-pruned plants. Even though the decrease in lateral dry

weight of root-pruned plants was not significant, it might indicate the relative importance

of root carbohydrates for initial lateral growth. In raspberry, the main source of

assimilates for growth of fruits and lateral apices is the nearest photosynthetic leaf

(Fernandez and Pritts, 1993; Prive et al.,1994), but root carbohydrates become important

for shoot growth when current carbohydrates availability is reduced (Fernandez and

Pritts, 1994).

The negative impact of root pruning on yield per cane was the result of the

reduction in flowers per cane and consequently the reduction in fruits per cane. Flower

bud formation occurs in the lower part of red raspberry canes as late as spring, right

before budbreak (Williams (1959). Additionally, pistils and anthers are still

differentiating in late April under cool temperatures (100 C average) (Qingwen and

Jinjun, 1998). Initiation and differentiation of flowers in raspberry require carbohydrate,

as found in other crops (Bodson and Outlaw, 1985; Darnell, 1991; Ooshiro and Anma

1998) and, because of the lack of photosynthetic leaves during flower differentiation,









carbohydrate requirements must be supplied by reserves from the previous year. Whitney

(1982) reported that red raspberry root dry weight decreased at budbreak and suggested

that assimilates from the root were mobilized to the floricanes and primocanes during this

time. In our experiment, there was also a decrease in root dry weight at budbreak,

although it was not significant compared with root dry weight at the time of root pruning.

However, root and whole plant carbohydrate concentration decreased significantly

between the time of root pruning and budbreak. The lower root carbohydrate

concentration in root-pruned plants compared to non root-pruned plants during budbreak

may have limited flower bud formation during budbreak, resulting in decreased yield

At the beginning of bloom (64 DAP), Pn was significantly higher in non root-

pruned plants than in root- pruned plants. This difference might result from the lower

fruit number in root-pruned plants, as lower fruit loads decrease sink activity and

consequently photosynthesis in some crops (Iglesias et al., 2002; Zhou and Quebedeaux,

2003; Urban et al., 2004). The difference in photosynthesis, however, disappeared at the

peak of harvest (102 DAP), possibly as a result of a decrease in the sink/source ratio as

bloom ended and more leaves attained photosynthetic competence. The higher Pn in non

root-pruned plants during bloom might explain the higher fruit soluble solids

concentration compared with fruits from root-pruned plants.

The higher soluble sugar and starch concentration in roots of non root-pruned

compared with root-pruned plants may be due to the higher photosynthetic rate in non

root-pruned plants. Floricane leaves serve as a source of assimilates for roots (Fernandez

and Pritts, 1993) and the movement of carbohydrate from floricanes to roots is common

once the floricane leaves are actively photosynthetic (Whitney, 1982).









During the growing season, roots need carbohydrates for growth as well as for

storage, and primocanes are the primary source of carbohydrates for the root (Whitney,

1982; Fernandez and Pritts, 1993). In the present experiment, primocane growth was

similar between the two root pruning treatments. Root growth rates were also similar, as

inferred from the absence of an interaction between root pruning and time of plant

harvest. However, the reduction of about 45% of the root system in the root-pruned plants

might decrease total root sink activity, resulting in increased carbohydrate concentration

in primocanes from root-pruned compared with non root-pruned plants. The higher

carbohydrate concentration in primocanes from root-pruned plants; however, was

apparently not sufficient to significantly decrease primocane photosynthesis.

Conclusion

Cane yield in red raspberry is decreased by dormant root pruning via the reduction

of flowers per cane; however, fruit size is not affected. The reduction of flowers per cane

in root-pruned raspberry plants appeared to be mediated by the reduction in root

carbohydrate availability at budbreak, when some flowers are still differentiating. This

decrease in carbohydrate availability was due to the loss of almost half the original

carbohydrate reserves after root pruning, even though the carbohydrate concentration in

roots was not affected by pruning. Carbohydrate concentration in other floricane

structures was not affected by root pruning, indicating that these organs are less

dependent than flowers on root carbohydrates for growth. Fruit set and fruit size

remained unaltered by root pruning, suggesting they may rely more on current than stored

photosynthates.









Table 6-1. Effect of dormant root pruning on dry weight allocation in 'Cascade Delight'
red raspberry in a winter production system in north Florida (n=4).


Factor
Treatment


Root


Root-pruned 75.2z 21.9
Non root-pruned 135.7 45.4
P-value 0.001 0.12
Harvest timey
Pruning 76.2bx ND"
Budbreak 61.6b 6.1b
End of fruiting 178.4a 61.2a
P-value 0.0003 0.01
zMeans of the same factor within the


Dry weight (g)
Laterals Floricane Primocane Fruits


27.0
37.9
0.12


155.9
130.9
0.67


36.5
67.8
0.003


Total

194.9
248.0
0.59


36.9 ND 137.6b
29.1 3.6b 58.2b
31.3 290.4a 468.6a
0.61 0.01 0.007
same column are different by t-test at the indicated


P-value.
YPlants were harvested at root pruning (11-16 Dec. 2004), budbreak (11 Mar. 2005) and
after fruit harvest (9 June to 16 July 2005)
xLSMean separation by Tukey at the indicated P-value
w No data available


Table 6-2. Effect of dormant root pruning on yield components of 'Cascade Delight' red
raspberry in a winter production system in North Florida (n=4)
Fruit set Yield/cane Fruit size


Treatment Flowers/cane Fruit/cane (%) (g)
Root-pruned 146.0 85.3 60.3 380.4
Non root- pruned 284.8 148.8 51.4 658.9
P-valuez 0.04 0.0006 0.7 0.01
zMeans within the same column are different by t-test at the indicated P-value.


(g)
4.32
4.46
0.64


Table 6-3. Effect of dormant root pruning on fruit quality of 'Cascade Delight' red
raspberry in a winter production system (n=4).
Soluble solids TA SSC/TTA


Treatment pH (%) (% Citric acid)
Root-pruned 2.99 9.3 2.6 3.5
Non root-pruned 3.09 10.3 2.5 4.2
P-valuez 0.283 0.06 0.18 0.002
ZMeans within the same column are different by t-test at the indicated P-value.


\






85


Table 6-4. Effect of dormant root pruning on leaf photosynthesis Pn of 'Cascade Delight'
red raspberry in a winter production system in North Florida (n=4).
Pn (imolm-2.s-1)
Treatment 64 DAPz 102 DAP
Floricanes
Root-pruned 3.80y 5.65
Non root-pruned 8.34 4.80
P-value 0.03 0.73
Primocanes
Root-pruned NDx 6.86
Non root-pruned ND 7.04
P-value 0.94
ZDAP=Days after planting
YMeans within the same column are different by t-test at the indicated P-value.
XNo data available















Table 6-5. Effect of root pruning and harvest time on carbohydrate concentration of 'Cascade Delight' red raspberry in a winter
production system in North Florida (n=6)

Glucose concentration (gg/mg dry weight)
Root Floricane Laterals Fruit Primocanes
Treatment Sol.Sug. Starch Total Sol.Sug. Starch Total Sol.Sug. Starch Total Sol.Sug. Starch Total Sol.Sug. Starch Total
Root-pruned 14.4' 45.9 60.3 22.3 34.6 57.0 65.0 29.1 94.1 113.5 11.5 125.0 40.0 31.8 71.9
Non root-pruned 17.6 53.4 71.0 19.3 34.4 53.7 61.4 33.4 94.7 107.9 2.4 110.3 26.7 26.2 53.0
P-value 0.47 0.10 0.06 0.41 0.98 0.76 0.51 0.37 0.93 0.21 0.23 0.13 0.09 0.36 0.04
Harvest timey
Pruning 23.8ax 49.6ab 73.4 21.0 44.7 65.7 83.9a 26.6ab 110.5a -
Budbreak 7.6b 35.8b 43.4 26.2 21.0 47.2 63.7b 24.9b 88.6ab 36.1 21.1 54.1
End of harvest 16.6ab 63.6a 80.2 15.2 37.8 53.0 41.9c 42.2a 84.2b 110.7 7.0 117.7 30.6 37.0 67.6
P-value 0.05 0.004 0.001 0.14 0.12 0.39 0.001 0.04 0.04 0.46 0.06 0.22
ZMeans of the same factor within the same column are different by t-test at the indicated P-value.
YPlants were harvested at root pruning (11-16 Dec. 2004), budbreak (11 Mar. 2005) and after fruit harvest (9 June to 16 July 2005)
XLSMean separation by Tukey at the indicated P-value



00
c>









Table 6-6. Effect of root pruning and harvest time on total carbohydrate concentration of
'Cascade Delight' red raspberry plants in a winter production system in North
Florida (n=4)
Glucose concentration (pg/mg dry weight)
Treatment Sol.Sugars Starch Total
Root-pruned 28.9z 35.6 64.4
Non root-pruned 26.2 41.1 67.3
P-value 0.37 0.10 0.49
Harvest timey
Pruning 29.8ax 44. a 73.9a
Budbreak 18.3b 27.5b 45.7b
End of harvest 34.5a 43.4a 77.9a
P-value 0.008 0.004 0.0005
zMeans of the same factor within the same column are different by t-test at the indicated
P-value.
YPlants were harvested at root pruning (11-16 Dec. 2004), budbreak (11 Mar. 2005) and
after fruit harvest (9 June to 16 July 2005)
xLSMean separation by Tukey at the indicated P-value














CHAPTER 7
SUMMARY AND CONCLUSIONS

The increasing interest in raspberry production in nontraditional growing regions in

the U.S. has resulted in the implementation and testing of new cropping systems. An

annual winter production system has been proposed for subtropical Florida (Knight et al,

1996). This system relies on naturally chilled bare-root long cane raspberry cultivars

obtained from northwestern nurseries and field-planted in south Florida during winter.

With this system, fruit harvest begins in early March, i.e. three months earlier than the

earliest ripening summer cultivars, which usually begin to produce ripe fruits in mid-June

in the western U.S. (WRRC., 2005).

Implementation of night's system in northern Florida, where severe freezes may

occur during winter, would require some adaptations. Polyethylene tunnels (Oliveira et

al., 1996) can provide protection during freezes and artificial heat will ensure sufficient

heat accumulation for uniform cane budbreak inside the tunnel (Carew et al., 1999).

Thus, tunnel production offers the possibility of advancing planting time, resulting in

fruit harvest earlier than March.

In this research, the feasibility of a winter raspberry production system under

polyethylene tunnels was determined. Two red raspberry cultivars, the summer bearing

'Tulameen' and the fall bearing 'Heritage', were compared each at two in-row spacings

(25 and 50 cm) with rows spaced at 1.8 m. Canes were planted on 28 Dec. 2001

following a chilling period of 1200 h at 40 C. Fruit harvest began in early March, 2002.

Yield per cane decreased at 25 cm compared with the 50 cm in-row spacing, but the




Full Text

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CARBON SUPPLY AND DEMAND IN AN ANNUAL RASPBERRY ( Rubus idaeus L.) CROPPING SYSTEM By HORACIO ELISEO ALVARADO RAYA A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2006

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Copyright 2005 by Horacio Eliseo Alvarado Raya

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This dissertation is dedicated with love to my wife, Maria Eugenia, and my daughter and son, Lorena and Erandi.

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iv ACKNOWLEDGMENTS I thank the members of my committee –Dr. Rebecca L. Darnell, Dr. Jeffery G. Williamson, Dr. Steven A. Sargent, Dr. Jonath an H. Crane and Dr. Jerry A. Bartz– for their guidance and support during my studies I especially thank Dr. Darnell for her encouragement and endless willingness to t each and help. I thank Steven Hiss for his limitless help during my studies. I also thank Paul Miller for his advises and help during my research. I want to thank Nicacio Cruz-Hue rta for his unselfish readiness to discuss and help during my research. I also would lik e to thank all my friends in “Mexicans in Gainesville” for their support during our firs t days in Gainesville and their company during our spare time; I thank them for all those precious memories. I want to especially tha nk the people of Mexico who economically supported my studies through the Mexican Council for Sc ience and Technology (CONACyT). I also want to thank the staff in CONACyT and my colleagues in the Universidad Autonoma Chapingo. Finally, I want to thank my parents (Fra ncisca Raya and Delfino Alvarado) for being my guide and inspirati on, and my brothers and sister (Angel, Erendira, Humberto and Heraclio) for their endless love.

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v TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES...........................................................................................................viii LIST OF FIGURES.............................................................................................................x ABSTRACT....................................................................................................................... xi CHAPTER 1 INTRODUCTION........................................................................................................1 2 LITERATURE REVIEW.............................................................................................5 Bramble Taxonomy......................................................................................................5 Raspberry Morphology.................................................................................................6 Raspberry Phenology....................................................................................................7 Raspberry Production.................................................................................................10 Plant Density in Raspberry.........................................................................................11 Alternative Cropping Systems in Raspberry..............................................................14 Raspberry Cropping in Mild-winter Areas.................................................................16 Root Pruning Effect on Yield.....................................................................................17 3 EFFECTS OF IN-ROW PLANTING DISTANCE ON YIELD IN A WINTER RASPBERRY ( Rubus idaeus L.) PRODUCTION SYSTEM....................................21 Materials and Methods...............................................................................................23 Plant Material......................................................................................................23 Planting System...................................................................................................24 Plant Growth........................................................................................................25 Fruit Chemical Analysis......................................................................................26 Experimental Design...........................................................................................26 Results........................................................................................................................ .26 Flowering.............................................................................................................27 Fruiting................................................................................................................27 Yield Components...............................................................................................28 Fruit Quality........................................................................................................29 Discussion...................................................................................................................29

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vi Cultivars..............................................................................................................29 In-row Spacing....................................................................................................31 Conclusion..................................................................................................................34 4 EFFECT OF INTENSITY AND TIMING OF GIRDLING ON WINTER RASPBERRY ( Rubus idaeus L.) PRODUCTION.....................................................39 Materials and Methods...............................................................................................42 Plant Material......................................................................................................42 Plant Growth........................................................................................................43 Girdling................................................................................................................44 Experimental Design...........................................................................................44 Results........................................................................................................................ .45 Flowering.............................................................................................................45 Fruiting................................................................................................................46 Yield Components...............................................................................................47 Dry Weight Allocation........................................................................................47 Fruit Quality........................................................................................................48 Discussion...................................................................................................................48 Bloom and Fruiting Period..................................................................................48 Yield Components...............................................................................................49 Dry Weight Allocation........................................................................................51 Fruit Quality........................................................................................................52 Conclusion..................................................................................................................53 5 EFFECT OF PRIMOCANE REMOVAL AND FLORICANE GIRDLING ON ‘TULAMEEN’ RED RASPBERRY ( Rubus idaeus L.) YIELD IN A WINTER PRODUCTION SYSTEM..........................................................................................60 Materials and Methods...............................................................................................62 Plant Material......................................................................................................62 Girdling and Cane Removal................................................................................63 Reproductive Measurements...............................................................................64 Photosynthesis.....................................................................................................64 Experimental Design...........................................................................................64 Results........................................................................................................................ .65 Discussion...................................................................................................................66 Conclusion..................................................................................................................68 6 ROOT PRUNING EFFECTS ON GROWTH AND YIELD OF RED RASPBERRY ( Rubus idaeus L.)...............................................................................73 Materials and Methods...............................................................................................75 Plant Material......................................................................................................75 Photosynthesis.....................................................................................................77 Carbohydrate Analysis........................................................................................77 Experimental Design...........................................................................................78

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vii Results........................................................................................................................ .78 Discussion...................................................................................................................81 Conclusion..................................................................................................................83 7 SUMMARY AND CONCLUSIONS.........................................................................88 APPENDIX A YIELD PER AREA IN WINTER 2003.....................................................................91 B DAILY TEMPERATURES........................................................................................92 LIST OF REFERENCES...................................................................................................95 BIOGRAPHICAL SKETCH...........................................................................................104

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viii LIST OF TABLES Table page 3-1 Flowering of ‘Heritage’ and ‘Tulameen ’ red raspberry as affected by in-row spacings in a winter producti on system in North Florida.........................................37 3-2 Fruit harvest period in ‘Heritage’ an d ‘Tulameen’ red as affected by in-row spacings in a winter producti on system in North Florida.........................................37 3-3 Reproductive development in ‘Heritag e’ and ‘Tulameen’ red raspberry as affected by in-row spacing in a winter production system in North Florida............38 3-4 Fruit quality in ‘Heritage’ and ‘Tulam een’ red raspberry as affected by in-row spacing in a winter production system in North Florida..........................................38 4-1 Flowering of ‘Willamette’ and ‘Tulameen’ red raspberry as affected by 75% girdling in a winter producti on system in North Florida..........................................54 4-2 Flowering of ‘Tulameen’ red raspberry as affected by girdling intensity in a winter production system in North Florida..............................................................54 4-3 Flowering of ‘Willamette’ red raspberry as affected by girdling intensity in a winter production system in North Florida..............................................................55 4-4 Fruit harvest of ‘Willamette’ and ‘Tulameen’ red raspberry as affected by girdling in a winter producti on system in North Florida..........................................55 4-5 Fruit harvest of ‘Tulamee n’ red raspberry as affected by girdling intensity in a winter production system in North Florida..............................................................55 4-6 Fruit harvest of ‘Willamette’ red raspberry as affected by girdling intensity in a winter production system in North Florida..............................................................56 4-7 Yield components of ‘Willamette’ and ‘T ulameen’ red raspberry as affected by 75% girdling time in a winter prod uction system in North Florida.........................56 4-8 Yield components for ‘Tulameen’ red raspberry as affected by girdling time and intensity in a winter pro duction system in North.....................................................57 4-9 Yield components of ‘Willamette’ red rasp berry as affected by girdling time in a winter production system in North Florida..............................................................57

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ix 4-10 Dry weight partitioning in ‘Willame tte’ and ‘Tulameen’ red raspberry as affected by girding time in a winter production system in North Florida................58 4-11 Dry weight partitioning in ‘Tulameen’ re d raspberry as affected by girdling time and intensity in a winter produc tion system in North Florida..................................58 4-12 Dry weight allocation pattern in ‘Willamette’ red raspberry as affected by girdling time in a winter produc tion system in North Florida..................................59 4-13 Fruit quality in ‘Tulameen’ red rasp berry as affected by girdling time and intensity in a winter producti on system in North-Florida .......................................59 5-1 Effect of girdling and primocane rem oval on bloom and fruiting in ‘Tulameen’ red raspberry in a winter production system............................................................71 5-2 Effect of girdling and primocane re moval on yield components of ‘Tulameen’ red raspberry in a winter production system............................................................71 5-3 Effect of girdling and primocane removal on dry weight allocation in ‘Tulameen’ red raspberry in a winter production system........................................71 5-4 Effect of girdling and primocane removal on leaf photosynthesis (mol CO2m2s-1) of ‘Tulameen’ red raspberry in a winter production system............................71 5-5 Effect of girdling and primocane remova l in ‘Tulameen’ raspberry fruit quality in a winter production system..................................................................................72 6-1 Effect of dormant root pruning on dry we ight allocation in ‘Cascade Delight’ red raspberry in a winter producti on system in north Florida........................................84 6-2 Effect of dormant root pruning on yi eld components of ‘Cascade Delight’ red raspberry in a winter producti on system in North Florida.......................................84 6-3 Effect of dormant root pruning on fruit quality of ‘Cascade Delight’ red raspberry in a winter production system.................................................................84 6-4 Effect of dormant root pruning on le af photosynthesis Pn of ‘Cascade Delight’ red raspberry in a winter produc tion system in North Florida.................................85 6-5 Effect of root pruning and harves t time on carbohydrate concentration of ‘Cascade Delight’ red raspberry in a winter production sy stem in North Florida ..86 6-6 Effect of root pruning and harvest time on total carbohydrate concentration of ‘Cascade Delight’.....................................................................................................87 A-1 Maximum estimated yield per area ob tained in an annual winter cropping system in North Florida and its compar ison with previously reported yield...........91

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x LIST OF FIGURES Figure page 3-1 Flowering in ‘Heritage’ and ‘Tul ameen’ red raspberry planted at in-row spacings of 25 (A) or 50 cm (B) in a wi nter production in North Florida (2002)....35 3-2 Fruiting in ‘Heritage’ and ‘Tulameen’ re d raspberry planted at in-row spacings of 25 (A) or 50 cm (B) in a winter production in North Florida (2002)..................36 5-1 Effect of girdling and primocane re moval on bloom (A) a nd fruiting (B) in ‘Tulameen’ red raspberry in a winter production system........................................70 B-1 Day, night and daily average temperatur es in tunnel during 2002 raspberry crop season in North Florida. Fruit harvest from 28 Feb to 16 May................................92 B-2 Day, night and daily average temperatur es in tunnel during 2003 raspberry crop season in North Florida. Fruit harvest from 11 Feb to 14 May................................93 B-3 Day, night and daily average temperatur es in tunnel during 2004 raspberry crop season in North Florida. Fruit harvest from 14 May to 12 July...............................94

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xi Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CARBON SUPPLY AND DEMAND IN AN ANNUAL RASPBERRY ( Rubus idaeus L.) CROPPING SYSTEM By Horacio E. Alvarado Raya August 2006 Chair: Rebecca L. Darnell Cochair: Jeffery G. Williamson Major Department: Horticultural Science As the interest in raspberry out-of-se ason production increase s, lucrative cropping systems need to be developed. This research studied the feasibility of an annual winter cropping system for raspberry in northern Fl orida. Bare-root canes of the fall-bearing ‘Heritage’ and summer-bearing ‘Tulameen ’ were shipped during fall 2001 from northwestern nurseries in the U.S. Canes we re planted in a polyethylene tunnel in December at either 25 or 50 cm in-row spacing. Fruit harvest began in March 2002. ‘Tulameen’ had higher yields per cane due to la rger fruit size, better fruit quality and a shorter harvest period than ‘Heritage’. Yi eld per cane decreased while yield per area increased by reducing in-row spacings. Ho wever, yield in both cultivars appeared reduced compared with previous work a nd below the national average of 10 ton/ha. Because root pruning during plant removal fr om the nursery is necessary for annual cropping systems, further experiments were conducted to determin e the importance of root carbohydrates on floricane yield.

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xii Canes of summer-bearing cultivars ‘Tulameen’ and ‘Willamette’ were completely girdled (100%), partially girdled (75%), or non-girdled. Partial girdling had no effect on floricane yield components or growth. Comple te girdling reduced cane flower number in ‘Tulameen’ and resulted in cane mortality in ‘Willamette’. In ‘Tulameen’, girdling done at the beginning of bloom decreased fruit number and yield per cane compared with the non-girdled control but had no effect on ‘Willa mette’ yield components. In a separate experiment, girdling ‘Tulameen’ at the peak of bloom decreased flowering and yield by ~25% compared with the nongirdled control; however, the differences were not statistically significant. Primocane removal di d not affect floricane yield components, but significantly decrease d root dry weight. In the summer-bearing ‘Cascade Delight’, dormant root pruning significantly reduced flower and fruit number and cane yi eld. Root pruning did not affect root carbohydrate concentration, but total plant carbohydrate concentration decreased significantly at budbreak. The annual raspberry cropping system studied in this research shows potential for winter production; however, root pruning decr eased cane yield. The decrease in the root carbohydrate pool resulting from root pruning likely had a detrimental effect on late flower differentiation during budbreak and consequently reduced yield.

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1 CHAPTER 1 INTRODUCTION The United States was the third largest raspberry producer in 2005, with yields reaching more than 10 ton/ha (Food and Agri culture Organization Statistical Database [FAOSTAT], 2005). However, only Washington, Oregon a nd Californian account for most of the U.S. raspberry production (Unite d States Department of Agriculture [USDA], 2005). During the last ten years, the total U. S. raspberry demand has exceeded its total production. From 1994 to 2004, the U.S. annually imported more than 10% of the raspberries sold in the market, with total values ranging from 9 to 41 million dollars per year (FAOSTAT, 2005). The increasing interest in growing raspberr ies in non-traditional areas results from the promising profits while filling the void in demand. Additionally, proposed cropping systems that allow raspberry harvest out of the traditional season (Pritts et al. 1999; Schloemann, 2001; Dale et al. 2005) may help in overcomi ng the seasonal low fruit availability in the market. In south Florida, Knight et al. (1996) proposed an annual system based on obtaining naturally chilled long canes from nurseries in the Pacific Northwest and field cropping them that sa me season under mild winter temperatures. With this system, fruit harvest began in early March. In northern areas in Florida, where freezing temperatures are common during wi nter, polyethylene tunnels (Oliveira et al. 1996a) can provide plant protection and h eat accumulation for early and uniform flowering (Carew et al. 1999).

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2 Although KnightÂ’s system demonstrated t echnical and biological suitability for raspberry production in tropical cl imates; the yield of ~1.4 ton/ ha in this system was far below the national average of ~10 ton/ ha as reported by FAOSTAT (2005). Selection of the appropriate cultivar and plant density for mild winter climates is important in order to optimi ze plant performance and profits Optimum temperatures for photosynthesis and growth in raspberry range between 20 and 25o C (Cameron et al. 1993; Fernandez and Pritts, 1994; Percival et al. 1996; Carew et al. 1999; Stafne et al. 2001), although there is cult ivar variability (Stafne et al. 2001). Similarly, the appropriate plant density is important for yield and fruit quality. Increasing raspberry plant densities increase yield per area (Freeman et al. 1989; Vanden Heuvel et al. 2000) up to an optimum; however, beyond this optim um yields per area decrease (Oliveira et al. 2004). Additionally, excessively high plant densities can reduce fruit size (Vanden Heuvel et al. 2000). Raspberry roots are a reserve for assimila tes during winter (Whitney, 1982). In the annual system proposed for south Florida, ro ots are severely dist urbed when removed from the nursery for shipping, with a c oncomitant reduction in the root carbohydrate pool. This is similar to root pruning, which ha s been shown to decrease growth and fruit size in apple (Schupp and Ferr ee, 1987; 1989), grape (Ferree et al. 1999; Lee and Kang, 1997) and sweet cherry (Webster at al ., 1997). The effect of root pruning on hormonal balance (Schupp and Ferree, 1994), water s upply (Geisler and Ferree, 1984; Schupp and Ferree 1990) and nutrient uptak e (Schupp and Ferree, 1990) in apple was temporary and could not explain the reducti on in growth of shoot and fr uit in this crop. Geisler and

PAGE 15

3 Ferree (1984) suggested that roots and shoot s compete with each other for carbohydrates after root pruning, causing shoot growth to slow. Carbohydrates appear to be essential for flower induction and formation in Sinapsis alba L. (Bodson and Outlaw, 1985), Vaccinium ashei Reade (Darnell, 1991) and Diospyros kaki L (Ooshiro and Anma, 1998). In ra spberry, flower differentiation in temperate climates begins in the upper cane during the fall previous to production and continues downwards. Flower formation slow s during winter and increases again in the lower cane in spring, right after budbreak (Williams, 1959; Qingwen and Jinjun, 1998). Furthermore, the root acts as a source of carbohydrate for the flori cane during these late stages of flower differentiation during budbr eak (Whitney, 1982; Fernandez and Pritts, 1993). Raspberry root carbohydrate pool may be reduced as a result of the severe pruning during cane removal and shipping in an a nnual system like that proposed for south Florida, resulting in decreased flower number and yield. Information on the source-sink relations in raspberry annual systems can be valuable for the appropriate primocane grow ing in the nursery during the summer and fall previous to removal and shipping. Cultural activities in the nursery that increase assimilates stored in the root can be imple mented to guarantee sufficient carbohydrate is available for production during th e same season the canes are removed from the nursery. Similarly, appropriate cultural/management techniques after canes are planted for production that same season could help alleviat e limitations in root carbohydrates that otherwise might decrease yield. The objectives of the present study were to 1) determine the effect of plant density on two raspberry genotypes grown under polyethylene tunnels in an annual winter production system, 2) determine the importance of roots and

PAGE 16

4 primocanes to floricane growth and yiel d, 3) assess the effects of root pruning on floricane growth and yield, a nd 4) assess the effects of r oot pruning on plant carbohydrate status during flowering and fruiting.

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5 CHAPTER 2 LITERATURE REVIEW Bramble Taxonomy The genus Rubus belongs to the Rosaceae family and is a very diverse taxa. Plants in this genus vary from herbs to woo dy plants (Bailey, 1941) and are distributed worldwide, from tropical to subarctic regi ons (Thompson, 1995) and from sea level to more than 4,000 m (Hummer, 1996). Diversity in the genus Rubus is due to polyploidy, apomixis, and hybridization. There are disagreements among taxonomists (Thompson, 1995), who classify this genus into 12 to 15 subgenera (Hummer, 1996) a nd approximately 740 species, most of them growing in North America (64%) and Asia (27%) (Gu et al. 1993). Three subgenera contain most of the diversity in this genus; two of them, Idaeobatus (the raspberries) and Rubus (the blackberries), are frequent ly cultivated (Hummer, 1996). Although polyploidy is very common in Rubus the species in the subgenus Idaeobatus are primarily diploid, and their origin is south and southeast Asia and North America (Thompson, 1995). Of the approximately 200 species registered for Idaeobatus (Hummer, 1996), Rubus phoenicolasius R. illecebrosus R. idaeus (the red and yellow raspberry), R. strigosus (the wild raspberry), and R. occidentalis (the black raspberry) are cultivated species (Bailey, 1949). The red raspberry possibly orig inated in the Magdalena Islands in the Gulf of St. Laurence (Bailey, 1941). However, other authors specu late that its center of origin is southwestern China (Gu et al. 1993) and southern Kazakhstan (Thompson, 1995). Most

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6 of the current red raspberry cultiv ars originated from crosses between R. idaeus and R. strigosus the wild raspberry from North America (Crandall, 1995). Raspberry Morphology Most plants in the genus Rubus are shrubs, with perennial root systems and biennial canes that vary from erect to trailing. The root system depth depends on the genotype and the soil conditions, with black raspberry root systems averaging approximately 90 cm in depth (Colby, 1936), and red raspberry ro ot systems averaging 180 cm in depth. However, 70% of the root dry weight is in the first 25 cm (Dana and Goulart, 1989). Horizontally, roots can grow up to 3.0 m from the main cane (Andersen et al. 1996) and are distributed symmetrically in all directions. Vegetative buds in roots are uncommon in black raspberry but present in red raspberry, where they are found randomly dist ributed on roots growing in the top 80 cm of soil (Colby, 1936). Andersen et al. (1996) found vegetative buds on lateral roots extending up to 3.0 m from the main cane. Cane elongation rate may vary, but the rate of node formation is nearly constant; thus, node number depends on cane length (Jen nings and Dale, 1982). Leaves have 3 to 5 leaflets and leaf axils may have one, two or even three buds. Usually, only one bud per axil breaks and forms a branch called the fruiting lateral. Fruiting laterals have leaves and a group of flowers (inflorescence) in each le af axil (Crandall, 1995) Flowers are usually white, although pink colors exis t (Bailey 1949). There are ma ny stamens arranged in two whorls around the receptacle a nd about 150 pistils arranged in a spiral on the receptacle (Crandall, 1995). Approximately 75 to 85 pi stils grow and coalesce to form the commercial berry (Dana and Goulart, 1989). In yellow and red raspberry, the berry separates from the receptacle when it is ha rvested and forms a hollow cone. The fruit may

PAGE 19

7 vary in size depending on the genotype. Gu et al. (1993) reported fruit of 0.4 g/berry in China. Commercial raspberri es bear fruits with aver age weights ranging around 1.5 g/berry (Hanson and Morales, 1997 ) to 6.0 g/berry (Pritts, 1999). Raspberry propagates by forming new shoot s from adventitious buds on the roots, as well as from axillary buds on the base of th e main cane. Adventitious buds are formed on the root during cool periods (from October to March in the Northern hemisphere) and can break during the subsequent fall; however, shoot growth occurs only in spring (Dana and Gulart, 1989). Axillary buds that form new shoots from the base of the main cane are called leader buds (Moore and Caldwell, 1985 ). Leader buds usually bear new shoots with faster growth rates and greater diam eters than shoots from root buds (Dana and Gulart, 1989). Once shoot growth begins, the new cane (now called the primocane) continues laying down nodes, leaves and axillary buds during spring and summer until temperatures drop below 15o C and days become shorter than 9 hours in the fall (Crandall, 1995; Williams, 1959). Except for the leader buds, which remain vegetative and will form primocanes in the following spring, most of the axillary buds on the primocane undergo floral initiation during summer and fall. The n, in spring, after a pe riod of differentiation, these buds break and form a fruiting lateral with leaves and axillary inflorescences (Moore and Caldwell, 1985). Raspberry Phenology Raspberry cultivars exhibit two main phenological behaviors: summer bearing and fall bearing behavior. In summer-bearing ras pberries, the primocane grows vegetative during the spring and summer. In fall, after th e cessation of terminal growth of the main cane, axillary buds undergo transition from vegetative to reproductive. Flower bud

PAGE 20

8 initiation (FBI) and early stages of flower bud differentiation (F BD) occur basipetally (Dana and Goulart, 1989). In winter, canes become dormant and in the following spring, FBD is completed, followed by budbreak and flowering (Jennings and Dale, 1982). In these types of raspberries, fr uits ripen from early to mid summer (University of Idaho, 2002). The beginning of FBI is characterized by a dome-shaped growing point inside the axillary bud. Later, this dome-shape point begins to produce leaf primordia, each one with an axillary inflorescence primordi um. This process is the inflorescence differentiation and will form the fruiting latera l. Flower differentiation then follows in each axillary primordium, beginning with the differentiation of sepal primordial, followed by the differentiation of petal, stam en and pistil primordia. Anthers and ovules are formed 2 or 3 days before the inflor escence is noticeable (Huang and Lei, 1998). Although the time for FBI and FBD is cont roversial, most authors agree that summer-bearing raspberries initiate flowers in early autumn (Moore and Caldwell, 1985). Moore and Caldwell (1985) observed that initia tion in Scotland occurs in mid-September and, two weeks later, the axis of the inflores cence is evident. By late October, flower primordia were differentiated and anther in itials and the perianth ring were evident. Flower diferentiation ceased during winter dormancy and rest arted the following spring before bud break. Huang and Lei (1998) observe d a similar time for flower initiation in Northeast China; however, development of th e terminal inflorescence primordia (future fruiting lateral) and its axillary inflorescen ces was slow but continuous during winter (October to mid-April). Floral primordia were evident after April, when the dormant buds began to break and form fruiting laterals

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9 In fall-bearing raspberries, FBI and FB D take place during the summer and fall on the primocane (Moore and Caldwell, 1985). Fruits appear in late summer or autumn on the tip of the primocane and some nodes be low it during the same year of vegetative growth. This upper-portion of the cane dies after cropping, while the basal portion can over-winter and bear fruit the following summer as a floricane (Keep, 1988). In ‘Heritage’, a fall-bearing red raspberr y, the first buds undergoing FBI are located in nodes 10, 11 and 12 below the cane tip. At th is time, the cane may be approximately 50 cm tall. Within three weeks cane height reaches 75 cm and all 12 upper buds may show floral development (Crandall and Garth, 1981). The importance of temperature and phot operiod in raspberry FBI and FBD is controversial. Williams (1960), studying the flowering behavior of the summer-bearing raspberry ‘Malling Promise’ in a glasshouse, did not observe FBI when plants were grown at 15.5o C regardless of the day length. Plants grown at 12.7o C and a 9 hour photoperiod for six weeks underwent FBI, however plants under the same temperature at 16 hour photoperiod did not. Plants grown at 10o C underwent FBI regardless of the photoperiod, although plants grown under a 9 hour photoperiod initiated flowers one week earlier than those under 16 hour photope riods. Williams concluded that photoperiod and temperature control the flowering habit of ‘Malling Promise’ raspberries. However, Vasilakakis et al. (1980) and Takeda (1993) found th at low temperat ures are not a requirement for raspberry FBI. They obtained flowering in ‘Heritage’ plants exposed to temperatures above 22o C throughout their development, although lower temperatures hastened the onset of flowering (Taked a, 1993). Although there is no information comparing the effects of temperature and photoperiod on FBI and FBD in summer

PAGE 22

10 bearing and fall bearing raspberry cultivars, the data suggest that summer bearing cultivars are sensitive to temperature and photoperiod, while fall bearing cultivars may be less sensitive. Like FBI and FBD, primocane growth is under temperature control. Williams (1959) found that cane growth of ‘Malling Promise’ under two daylengths (9 and 16 hours) was temperature sensitive. Canes grown at 21o C grew continuously during a two month period regardless of the daylengt h. In contrast, canes maintained at 10o C grew less than two centimeters the fi rst 20 days, and then cane growth stopped regardless of the daylength. This behavior was also observed by Vasilakakis et al. (1980) who obtained a longer vegetative growth phase in fa ll-bearing ‘Heritage’ canes grown at 22o C compared with canes grown at 7o C. Canes maintained at 22o C flowered at 80 nodes of growth, while canes grown at 7o C flowered at 28 to 32 nodes of growth. Carew et al. (1999) observed an optimum node production ra te occurring in fall-bearing ‘Autumn Bliss’ growing at 22o C; above and below this temp erature, node production slowed. Similarly, plants of fall-bear ing ‘Autumn Bliss’, ‘Heritage ’ and ‘Redwing’ grew more and produced more nodes, flowers and fruits as soil temperature increased (Prive et al. 1993). Raspberry Production Since 1997, the United States has been am ong the six countries with the greatest cultivation of raspberry and the highest yi elds per hectare. In 2005, the US had 6,100 hectares of cultivated raspberry, surpassed only by the Russian Federation, Serbia and Montenegro, and Poland. The yield per area in the U.S. ranked th ird in 2005, with 10.2 ton/ha (FAOSTAT, 2005). Thr ee states, Washington, Oregon and California, account for

PAGE 23

11 most of the US raspberry production from June to October (USDA, 2005) and the demand for the product exceeds the domestic production. Although the United States is the third larg est raspberry producer in the world, as much as 12% of its domestic demand for raspberry fruit in 2004 was met by imports (FAOSTAT, 2005). Imported raspberry fruits averaged 8,925 tons in 2004 (FAOSTAT, 2005). Most of the imports are arriving from Canada and Chile year-round and from Mexico from October th rough May (USDA, 2006). Increasing the cultivated area and/or the yi eld of raspberry in U.S. may be options for increasing the fruit supply by domesti c production. Yield increases are obtained by selecting high yield cultivars or by increasing plant density of the crop. Plant Density in Raspberry Row and plant spacing as well as the number of primocanes per plant determine the cane density in raspberry plantations. Between -row distances vary according to the plant vigor, trellising system and harvesting me thod. Though plant vigor depends on varietal characteristics, variations on climate may in fluence the plant growth rate. Red raspberry grows more vigorously in the Pacific Nort hwest US than in the Northeast US and Canada, requiring between-row spacings of 2.4 to 3.0 m, while betw een-row spacings in the Northeastern U.S. vary from 1.8 to 2.4 m (Crandall, 1995). Plants trained in V and Ttrellis require wider between-ro w distances than plants trai ned in upright trellises. Plantations planted for machine harvest must have between row spacings wide enough to permit the machine move along the al leys without damaging plants. In-row planting distances are determined not only by cultivar vigor, but by the training method. In-row spacing is closer when pl ants are trained in hedgerows than when

PAGE 24

12 plants are maintained in hills (Crandall, 1995). In either case, the aim is to achieve the highest yield per area with acceptable fruit quality. Raspberry yield results from the inte raction among several vegetative and reproductive components, including number of canes per plant (hill), number of plants per area, number of nodes per cane, percent of fruitful nodes, number of fruits per node, fruit weight (Hoover et al. 1988) and lateral length (Freeman et al. 1989) From these, the yield components that most strongly affect marketable yi eld are number of canes per hill (Hoover et al. 1988; Freeman et al. 1989; Gundersheim and Pritts, 1989), number of buds per cane (Gundersheim and Pritts, 1989), lateral length (Freeman et al. 1989) and number of fruits per node (Hoover et al. 1988). Yield increased si gnificantly in ‘Royalty’ purple raspberry by increasing cane density fr om 4 to 12 canes per hill (Gundersheim and Pritts, 1991). Vanden Heuvel et al. (2000) found a significant lin ear increase in yield per area of ‘Titan’ red raspberry as cane density increased from 9 to 30 canes per square meter. Similarly, Freeman et al. (1989) reported that cane nu mber per hill contributed up to 24% of the total marketable yield in si x raspberry culitvars. Increasing cane number per hill will result in more fruits per area and consequently more yield per meter of row up to an optimum cane density. Beyond this optimum; however, yield per area will decrease (Oliveira et al. 2004). The impact of plant density on total yi eld usually interacts with other yield components and compensation among them is common. In ‘Heritage’ raspberry, yield of plants at 25 cm in-row spacing was 99% higher th an yield in plots with plants spaced at 100 cm (Myers, 1993). In this case, plant densit y affected yield per area by increasing the number of fruiting primocanes at the shorter in-row spacings rather than increasing the

PAGE 25

13 yield per cane. Similarly, Vanden Heuvel et al. (2000) found that cane density has a negative linear effect on fruit size, but in creasing the cane density will result in more fruits per area. Therefore, th e selection of the proper number of plants per area should consider the effect of plant density on rela ted yield components in order to achieve good yields and acceptable fruit quality. The increases in raspberry yield obtained by higher cane densities at the expense of decreases in other yield components make the raspberry plant an in teresting system for studies on carbon mobilization and interp lant competition. In “Washington’ red raspberry, hills with either ni ne or 12 canes yielded more grams fruit per hectare than hills with six canes; however, there were more fruiting laterals per cane, more fruits per lateral and consequently more fruits pe r cane in hills with six canes (Crandall et al., 1974). Hoover et al. (1988) reported a significant nega tive correlation (r=-0.491; p=0.05) between cane density and number of fruits per node in ‘Heritage’ red raspberry. However, Myers (1993) reported that in-row spacings of 25, 50 or 100 cm had no effect on total number of fruiting nodes per primocane in ‘Heritage’. Sullivan and Evans (1992) found a significant negative correlation (r = -0.61 to -0.77) between cane density and yield per cane in a three-year experiment with four red ra spberry cultivars. Similarly, Myers (1993) and Vanden Heuvel at al (2000) documented the ne gative effect of high plant and cane densities on fruit size of red raspberry. Goulart and Demchak (1993) found a negative effect of high densities on fr uit size of black raspberry. However, even though high cane densities decreas e fruit size and fruit number, increased density often results in higher yields per area (Mye rs, 1993; Gundersheim and Pritts, 1991; Vanden Heuvel et al. 2000).

PAGE 26

14 The harvest season of raspberry is well defi ned from June to October in the U.S. Additionally, the perishability of the fruit lim its its postharvest storage life. Considering this situation, despite the increases in yield per area obtained by increasing plant densities, the availability of raspberry fruit year-round ha s to be achieved by extending the harvest season. Alternative Cropping Systems in Raspberry Most of the cropping systems that focus on extending the harvest period are based on the use of chemical products, cultural pract ices and/or climate simulation to force the plant to flower in a season different from the normal one, and advance or delay harvest. Raspberry has been grown in mild-winter conditions, where endodormancy is overcome by spraying with oil + di nitro-o-cresol (5%), KNO3 (5%), thiourea (1%) or hydrogen cyanamid (4%) in late winter or early spring. These treatments also advance the flowering time compared with untreated controls (Snir, 1983). Summer pruning by cutting the primocanes at different heights and dates during summer and permitting the remaining buds to sprout and form new primocanes, has been used to advance flowering and obtain winter fruits in fall-bearing raspberries like ‘H eritage’, ‘Autumn Bliss’, and ‘Autumn cascade’; however, the date and intens ity of pruning are critical for determining the harvest period and yield (Oliveira et al., 1996a, Oliveira et al. 1996b). ‘Autumn Bliss’ canes pruned in early summer and grown in an unheated greenhouse yielded 26.5 to 63.5 g/cane throughout the fall, while thos e pruned in late summer yielded only 2.1 to 4.8 g/plant during the winter (Oliveira et al. 1996b). Although growing raspberries in greenhouses allows manipulation of the harvest season by advancing or delaying flowering, th e harvest period must occur when fruit prices are high in order to recover the investment in energy and infrastructure.

PAGE 27

15 Additionally, the croppin g system must produce high yields. Dale et al. (2001) suggest that earlier fruiting cultivars are more a ppropriate for winter greenhouse production than late fruiting cultivars because early cultivar s increase the harvest season by merging the fall harvest period on the primocane with th e summer harvest period on the floricane. Another alternative for ras pberry cropping is the use of plants that have been naturally or artificially chilled, and then grown inside a heated greenhouse during the winter. Fall-bearing ‘H eritage’ plants natura lly chilled for more than 1000 chilling units (CU) before moving them into a heated greenho use in winter flowered in less than three months; however, the author does not mention the effect of the treatment on fruiting and yield (Takeda, 1993). Pritts et al. (1999) proposed a technique to grow winter raspberries in the Northeast United States. Tissue-cultured raspberry plugs were planted in containers in May, grown outside until mid-December to receive sufficient natural chilling, and then moved into a heated greenhouse at 13-18o C. Harvest began 10 weeks later in February and March. After harvest, the plants were tr ansplanted to larger containers and grown outside again to begin anothe r crop cycle. It was proposed that growers using this technique could harvest $2000 to $4000 (660 half pints) worth of high quality fresh winter fruits in a 6.0 x 9.0 m house. This sy stem has already been utilized commercially and some problems remain to be solved. Pollin ation was poor because of the low activity of bees and the investment is not returned until the second year of cropping when yields increase up to 400% over the first cropping year (Schloemann, 2001). Although the profitability in Pritts’ proposed system makes this technique attractive, using heated greenhouses through the winter and supplying additional light

PAGE 28

16 elevates cropping costs. This can be overcome if plants ar e grown in subtropical areas with mild winters Raspberry Cropping in Mild-winter Areas Mild winters in subtropical regions allo w earlier harvest of ra spberries compared with traditional cropping systems by using pre-chilled plants in an annual production system. Knight et al. (1996) purchased pre-chilled ‘H eritage’ plants from commercial nurseries in Washington and fiel d planted them in late January in Florida. In floricanes, harvest occurred from late March through early September and yield averaged 2,112 kg/ha. Primocanes arising from roots in spring fruited from late May through early September and accounted for 1,460 kg of fruit per he ctare. The key point in this system is to provide plants with suitable temperatures in the nursery in order to break dormancy, as well as in the field in order to obta in uniform bud break after planting. Since photoperiod is not a requirement fo r dormancy release in raspberry (Heide, 1993), temperature becomes the key factor fo r successful bud break after the chilling requirement has been met. Heat units (HU) appear to have an important role in the timing of flowering after planting. ‘Heritage’ pl ants grown at 29/24o C (day/night) flowered two weeks earlier than those grown at 25/20o C (Lockshin and Elfving, 1981). However, Hoover et al. (1989) were not able to explain the difference in ha rvest date betw een ‘Heritage’ and ‘Redwing’ growing in different locations and differe nt years on a HU accumulation basis, although they found a high correlation betw een cane growth and HU. It is likely that an interaction between genotype and environment aff ects flowering onset (Jennings, 1979). Growers producing raspberries in subtropi cal conditions are faced with potential problems of high light inte nsities, temperatures, a nd humidity effects on plant

PAGE 29

17 development and fruit quality. Raspberry net photosynthesis is optimum at plant temperatures of 20o C compared with 25 or 18o C (Percival et al. 1996). Average temperatures in the subtropics exceeds this optimum and high temperature in combination with high light intensity and lo w relative humidity reduces raspberry fruit size and increases the inciden ce of sunburn, a disorder that results in discolored dry drupelets in the fruit (Crandall, 1995). Therefore, a balance in light intensity must be achieved in order to develop fruit color and soluble solids while avoiding detrimental effects. Another potential problem that arises in subtropical wi nter production systems for raspberry is the disturbance of the root sy stem during digging and transport that may result in problems with fruit size and quality. Since plants are grown as annuals in this system, there is little time for the root syst em to recover before flowering and fruiting begin. Thus raspberries canes grown in this system may respond as if they were root pruned. Root Pruning Effect on Yield Root pruning may reduce yield by decrea sing fruit size or decreasing fruit number per cane. The effect of root pruning on fru it size will depend on fruit load, the time and intensity of pruning, cultivar, and water and nutrient suppl y (Bradlwarter and Knoll, 1996). Dormant root pruning is commercially used in high density plantations and strongly reduces vegetative growth, but also fruit size in apple (Schupp and Ferree, 1987; 1989), grape (Ferree et al. 1999; Lee and Kang, 1997) and sweet cherry (Webster at al ., 1997), but root pruning at the beginni ng of flowering had no significa nt effect on apricot fruit size (Arzani et al. 1999). Similarly, Elfving et al. (1991) found no effect of root pruning

PAGE 30

18 at full bloom on fruit size of ‘Macspur McIntosh’/M7 apple. However, Schupp and Ferree (1989) found a reduction in fruit size, shoot length, leaf size and trunk cross sectional area in ‘Melrose’/M7A apple trees r oot pruned either during dormancy or at full bloom, with the strongest reductions found with dormant root pruning. The root pruning effect on fruit size coul d be mediated by alterations in hormone synthesis and transport, water relations, nutrient uptake and/or assimilation and/or source–sink relationships (Fe rree, 1992). However, previ ous studies have shown the temporary effect of root pruning on hormona l balance (Schupp and Ferree, 1994), water supply (Geisler and Ferree, 1984; Schupp a nd Ferree 1990) and nutri ent uptake (Schupp and Ferree, 1990). Geisler and Ferree (1984) suggested that competition for assimilates between roots and shoot may cause the reductio n in shoot and fruit size in root pruned apple Carbohydrate translocation from shoot to root after root pruning was observed in grape by Ferree et al. (1999). A decrease in cane dry we ight and an increase in root dry weight was observed in root-p runed compared with non root-p runed vines. Root pruning decreased the starch content in leaf chloroplasts of de blossomed apple trees (Schupp et al. 1992), possibly due to mobilization of assi milates from shoot to root during the intense root growth season. In raspberry, roots compete with shoots and fruits for carbohydrates and can constitute a strong sink du ring active growth; in this way, they can limit shoot and fruit growth (Fernandez and Pritts, 1994). Furthermore, raspberry root regeneration is concomitant with florican e and primocane growth (Atkinson, 1973) and may be intensive in the re gion near the cut (Schupp et al. 1992). The potential

PAGE 31

19 carbohydrate translocation from shoot to ro ot after root pruning in raspberry may negatively impact the fruiting. Besides the possible root si nk activity during active grow th, roots may also play a source role during budbreak. Fe rnandez and Pritts (1993) f ound reductions in root dry matter concomitant with fl oricane dry matter increases at budbreak. Additionally, Whitney (1982) observed carbohydrate mobilizati on in the floricane from the cane to the newly growing laterals during budbreak. The importance of adequate carbohydrate supply to floral buds has been demonstrated in Sinapsis alba (Bodson and Outlaw, 1985), blueberry ( Vaccinium ashei ) (Darnell, 1991) and persimmon ( Diospyros kaki L) (Ooshiro and Anma, 1998). In raspberry, a decreased carbohydrate pool in the root at budbreak could decrease flower formation in the lower parts of the floricane, which are initiating and differentiating during this time (Williams, 1959; Qingwen and Jinjun, 1998). The effect of root pruning on cane yiel d and on the source-sink relationship in raspberry has not been studied. The annual life of the canes and the continuous generation of primocanes, which increase th e competition between shoot and roots for assimilates, makes raspberries an inte resting model for studying source-sink relationships. In raspberry plants with intact root systems, the leaves nearest the fruiting lateral are the main source of assimilates for fruits of that same lateral, however, some of the fixed carbon in primocanes and floricanes is translocated to the roots (Fernandez and Pritts, 1993; Prive et al. 1994). Roots translocate carbohydrat es to the floricane during budbreak and peak of harvest but they im port current year photosynthates from primocanes and floricanes during the beginni ng of fruiting (Fernand ez and Pritts, 1993).

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20 The annual cropping system of winter raspbe rry is based upon the use of naturally or artificially chilled bare root canes that are removed fr om the nursery and cropped that same year. The perturbation of the root sy stem during removal from the nursery and shipping may have similar effects on yield to those observed in other root pruned fruits (Schupp and Ferree, 1987, 1989; Ferree et al., 1999; Lee and Kang, 1997; Webster at al ., 1997). Information on the effect of root pruni ng on yield of raspberry plants grown under this system is necessary in order to develop the best plant management that will result in maximal fiscal returns for the crop.

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21 CHAPTER 3 EFFECTS OF IN-ROW PLANTING DISTANCE ON YIELD IN A WINTER RASPBERRY ( Rubus idaeus L.) PRODUCTION SYSTEM In 2005, the United States was the third la rgest producer of raspberry. Only the Russian Federation and Serbia and Monteneg ro surpassed the US in total raspberry production. The U.S. reported 6,100 hectares of cultivated raspberry in 2005, with yields up to 10,164 ton/ha. However, these yields are below those reported for Romania (21,000 ton/Ha) and Mexico (12,035 ton/Ha) (FAOSTAT, 2005). The relatively low yields per area attained in U.S. indicate an unfulfilled yield potential for raspberry production in this country. Additionally, only Washington, Oregon and California account for most of the U.S. raspberry production from June to October (USDA, 2005). This situation makes the total production in this c ountry insufficient to meet the high domestic demand for this fruit. In order to fulfill the demand, the U.S. imported 12% of the raspberries sold in 2004, with a total value above $41.4 million (FAOSTAT, 2005). The U.S. imports raspbe rries year-round from Chile and Canada, while Mexico supplies fruits from Oct ober through May (USDA, 2006). The high perishability of raspbe rry fruits further limits domestic s upply of this berry. Fruits cannot be stored for more than one week and tran sport requires meticulous technology to avoid quality losses, resulting in a stationary and localized domestic raspberry production. Raspberry production out of season and/or in non-traditional growing regions results in a higher value product that could mitigate the short supply across the country during the year. The increasi ng interest in off-season ra spberry production, as well as

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22 production in non-traditional regions, is driv ing the proposal of several new production systems. In New York, naturally chilled ca nes are moved to heated greenhouses in the fall, resulting in fruit harv est during February, when pric es can be $6.00 USD/half pint (Pritts et al. 1999). However, the costs for constructing, maintaining, heating and ventilating the greenhouses still may make th is system prohibitive for small growers. Raspberry production in subtr opical regions may alleviat e the high investments for winter production. Knight at al (1996) obtained ra spberry fruits in South Florida from late March through early September by purchasi ng naturally chilled canes from nurseries in Washington and field planting them in late January. The chilling temperatures in the nursery followed by the mild winter conditi ons in south Florida overcame dormancy and avoided the expense of building and heati ng a greenhouse, as proposed by Pritts for Northeast U.S. However, new problems come w ith these new systems, and they must be solved in order to maximize revenues for th e grower. Selection of the proper cultivar, planting density, irrigation a nd fertilization regimes, and pest and disease control practices are some of the new topics that mu st be addressed in these production systems. Planting density will depend to some extent on the cultivar vigor, as the goal is to achieve the highest yield without negatively affecting fruit qu ality. In raspberry, yield is the result of the interaction of several vegetative and repr oductive components, such as cane density, nodes per cane and fruits per node (Hoover et al. 1988; Freeman et al. 1989; Gundersheim and Pritts, 1989). Increa sing cane density from 9 to 30 canes/m2 significantly increased yiel d per area of ‘Titan’ red raspberry (Vanden Heuvel et al. 2000). Yield component analysis revealed th at cane number per hill accounted for ~ 25% of the total marketable yield in several summ er bearing red raspberry cultivars (Freeman

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23 et al. 1989). In a three year experiment with ‘Heritage’ re d raspberry, yield the first year at 25 cm in-row spacings was 99% higher than yields at 100 cm in-row spacings, with no differences in yield the following two years (Myers, 1993). However, the yield increase resulted from an increase in fruit number per area rather than an increase in cane yield, which typically decreases by increasing can e densities (Sullivan and Evans, 1992; Vanden Heuvel et al. 2000). Decrease in cane yield with increasing planting density is apparently due to a decrease in fruit size (Myers, 1993; Goulart and Demchak, 1993; Vanden Heuvel et al. 2000). Planting density may also affect fruit ch emical composition by altering the amount of light reaching the fruiting la terals and developing fruits. Fruit soluble solids decreased and fruit pH increased on partially shaded laterals of hedgerow planted canes compared with better light exposed laterals of V-trellised canes (Vanden Heuvel et al. 2000). In an annual winter raspberry production system in subtropical climates, the proper cultivar and planting density is important in order to maximize revenues for the grower and make the system profitable. The select ed plant in-row spacing should be dense enough to ensure high yields without decreasi ng fruit quality and nutritional value. This experiment was performed to determine the e ffect of cultivar and plant in-row spacing on raspberry yield components and fruit quality in an annual winter production system under plastic tunnels in a subtropical climate. Materials and Methods Plant Material Dormant bare-root canes (120 to 150 cm l ong) of ‘Tulameen’ and ‘Heritage’ were purchased in Nov. 2001 from a commercial nur sery in the Northwest United States. Canes were grouped in sets of 50 and their r oots were covered with wet cypress sawdust

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24 and wrapped with clear plastic. Each group of canes was placed in a darkened walk-in cooler at 4o C for 1200 hours. Canes were not watered during chilling. ‘Tulameen’ is a summer-bearing genotype released in the late 1980’s by the Agriculture Canada Research Station in Br itish Columbia. It is a large fruited, high yielding cultivar with a late ripening seas on in the Northern US and South Canada (Daubeny and Anderson, 1991). ‘Heritage’ is a fa ll bearing genotype released in the late 1960’s from Cornell University and is the most widely planted red raspberry cultivar in the world (Daubeny et al. 1992). The success of ‘Heritage’ may rely on its fruit firmness and shelf-life, as well as its relatively lo w chilling requirement and heat tolerance (Daubeny et al. 1992). Planting System. On December 28th 2004, canes were moved out of the cooler and planted in the beds inside a polyethylene tunne l at the University of Florid a at Gainesville, FL (29.69N and 82.35W). The tunnel was a Quonset styl e (26.8 m long x 3.6 m wide x 3.3 m high) covered with 0.15 mm thick ultraviolet resistant polyethyl ene film. Minimum temperature inside the tunnel was maintained above 10o C by placing electrical heaters (Dayton; 6.1 to 17.1 BtuH; model 3UG73) in the central aisle. Ventilation was provided by raising the polyethylene film to a height of 2.0 m on both sides of the tunnel. There were two beds inside the tunnel; each bed (26 m long, 60 cm wide and 20 cm depth) was filled with a mixture of perlite :vermiculite:peat (1:1:1). Temperature was registered daily every five minutes with a HOBO ProS eries (H08-030-08. Bourne, MA. USA). The HOBO was placed 1.5 m above the soil and dir ectly underneath a rain shield (11 cm diameter).

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25 Canes were centered in their respective beds, resulting in 180 cm distance between rows. Two in-row distances, 25 and 50 cm, were tested. The trellis sy stem consisted of two wires along the bed at 60 and 170 cm above soil level. Wires were tied to a wooden post at each end and canes were tied to the wires with flagging ta pe. A drip irrigation system consisting of polyethylene lines and mi crotubes was installed along the center of each bed. There was one microtube per cane co nnected to the line with a spot spitter (Roberts irrigation, San Marcos, CA. USA) delivering 340 mL water per minute. Plant Growth. Canes were irrigated daily with 3.4 L of water from 9:00 to 9:10 EST (13:00 to 13:10 GMT) and fertilized every week with 20-8.8-16.6 water soluble fertilizer (J.R. Peters, Inc. Allentown, Penn.) at a rate of 0.6 g of nitrogen (N) per plant. Throughout the fruiting season (mid-Febru ary to mid-May 2002), all primocanes were pruned to the soil level once they reached 20 to 25 cm long. Fungicide sprays started one month after planting, before ve getative budbreak was evident. Captan 50WP (5.6 Kg/Ha) was sprayed for control of Botry tis every 7 to 10 days throughout winter and spring. Flowering began ~40 (Heritage) or ~50 (Tulameen) days after planting (DAP) and flowers were counted on all plants. Fr uit harvest began ~75 (Heritage) and ~87 (Tulameen) DAP, and fruit were weighed at each harvest. Fruits were considered ripe and ready for harvest when they were fully red. At this time, a soft pull was sufficient for separating the fruit from the core. The peak of fruiting was estimated as one month after the peak of flowering and fruits harvested during this time were used for chemical analysis after weighing.

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26 Fruit Chemical Analysis. Fruits were hand squashed and filtered th rough three layers of cheesecloth. Juice was centrifuged for 20 minutes at 2000X g The supernatant was decanted and used for soluble solids content (SSC) and total titr atable acidity (TTA) measurements. Fruit soluble solid were determined with a re fractometer (Atago PR-101. Tokyo, Japan). Total titratable acidity was determined as percent of citric acid by diluting six mL of the supernatant with 50 mL distilled water and titrating with 0.1 N NaOH to a final pH of 8.2. Milliliters of NaOH were reco rded and titratable acidity (a s citric acid equivalents) was calculated by the formula given by Garner et al. (2003): % citric acid = [(mL NaOH) x (0.1) x (0.064) x (100)]/ 6. The millequivalent factor of 0.064 was used for citric acid. Experimental Design A 2x2 factorial was used in this experi ment, with two cultivars (‘Heritage’ and ‘Tulameen’) and two in-row spacings (25 and 50 cm) as the factors. The resulting four treatments were arranged in a randomized co mplete block design with seven replications. Each replication was comprised of five plan ts and data were taken only from the three middle plants. These three plants together we re considered an experimental unit. Data were analyzed using SAS (SAS inst itute Inc., Cary, NC USA. 2002). Results There were no interactions between cultivar and in-row spacing on variables other than bloom period length; therefore, only main effects will be presented and discussed. The cool winter temperatur es inside the tunnel (Fig. B-1) were favorable for incidence of diseases like cane Botrytis ( Botrytis cinerea Pers.:Fr.) and Phytophthora root rot ( Phytophthora spp.). The application of fungici des on a regular basis after the

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27 observation of symptoms was essential to avoid disease progression and visible fruit infections. There were fourteen frosts (temperatures below 0o C) in this area during the 2001-02 winter and the electric heaters were able to maintain the tunnel temperature above 5o C during these freezing events. Flowering Flowering began significantly earlier in ‘H eritage’ than in ‘Tulameen’ (Fig. 3-1A and Table 3-1). When flower counts began 43 DAP, ‘Heritage’ already had an average of 10 flowers per cane; however, ‘Tulameen’ di d not begin to flower until 50 DAP. The difference in the beginning of flowering resulted in a longer flowering period for ‘Heritage’ compared with ‘Tulameen’ (Table 3-1). There was no difference in the time to 50% flowering in either cultivar, which o ccurred in mid-March (~78 DAP) (Fig. 3-1A). In-row spacing did not affect the beginning of flowering, but plants spaced at 25 cm in-row reached 50% flowering significantly ea rlier than plants spac ed at 50 cm (Table 3-1), and plants spaced 25 cm in-row had a s horter flowering period than plants spaced at 50 cm in-row. The pattern of flowering at both distances was similar and a peak of flowering was evident at ~78 DAP (Fig. 3-1B). Fruiting Fruiting followed a similar pattern as flow ering, and fruit harvest began 12 days earlier in ‘Heritage’ than in “Tulameen’ (F ig. 3-2A and Table 32). Additionally, fruit harvest ended 3 days later in ‘Heritage’ than in ‘Tulameen’ (Table 3-2), resulting in a 15day longer fruit harvest period for ‘Heritage’. The fruit development period, estimated as the time from 50% flowering to 50% fruit ha rvest was significantly shorter in ‘Tulameen’ compared with ‘Heritage’ (30 and 35 days respectively) (Table 3-2).

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28 In-row distances did not affect the beginni ng of fruit harvest, and canes of both cultivars began fruiting about 80 DAP (i.e. 34 days after the beginni ng of bloom) (Figure 3-2B and Table 3-2). In-row spacing did not affect the fruit development period; however, 50% fruit harvest occurred later on can es spaced at 50 cm compared with canes spaced at 25 cm (Table 3-2). This resulted in a longer fruit harvest period for canes at the 50 compared to the 25 cm in-row spacing. Fru it harvest was concen trated between 102 and 129 DAP for canes at both in-row spacings (Figure 3-2B). Yield Components There was no statistical difference between cultivars in flower number per cane, which averaged 106 and 115 in ‘Heritage’ a nd ‘Tulameen’, respectively (Table 3-3). Both cultivars had similar fruit set percentage s, thus there was no significant difference in fruit number per cane between cultivars. However, ‘Tulameen’ fruits were ~ 78% larger than ‘Heritage’ fruits (3.1 and 1.7 g per fr uit, respectively) and this resulted in ‘Tulameen’ canes yielding about 80% more than ‘Heritage’ canes (Table 3-3). On a per hectare basis, yields would average 2600 kg for ‘Heritage’ and 4900 kg for ‘Tulameen’ (Table 3-3). Canes spaced at 25 cm in-row had significan tly fewer flowers than canes spaced at 50 cm (Table 3-3). However, fruit set was not affected by in-row dist ances, and averaged ~90%. The difference in flowers pe r cane resulted in more fruits per cane at 50 cm than at 25 cm in-row spacing (118 vs 80 fruits per cane respectively). Fruit size was not affected by in-row distances, thus, the difference in fr uit number per cane was responsible for the increased yields in canes spaced at 50 cm (287 g/cane) compared with canes spaced at 25 cm (192 g/cane) (Table 3-3). When the yield per cane is extrapolated to a per hectare basis, canes spaced at 25 cm yielded more than canes spaced at 50 cm (4300 vs 3200 kg,

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29 respectively) (Table 3-3). The maximum estim ated yield per area obtained in the present experiment is compared with previously report ed yields for the cult ivars studied in Table A-1. Fruit Quality Two sampling times were chosen for fruit qua lity analysis; the first at peak fruiting and the second 7 days later (April 9 and 16,2004) ‘Heritage’ fruit ti tratable acidity was significantly greater th an ‘Tulameen’ fruits at both sampling times, averaging 1.1% for ‘Heritage’ and 0.8% for ‘Tulameen’ (Table 3-4) There were no consis tent differences in fruit SSC between the two cult ivars. However, SSC were si gnificantly lower in fruits from 25 cm than in fruits from 50 cm at both sampling times (13.64 vs 14.21 %, respectively, on April 9 and 12.60 vs13.17 %, re spectively, on April 16). ‘Tulameen’ had higher SSC/TTA ratios than ‘Heritage’ but in-row spacings had no c onsistent effect on this ratio. Discussion Cultivars The earlier bloom and fruiting periods obs erved in ‘Heritage’ compared with ‘Tulameen’ may reflect genotypic differences between fall bearing and summer bearing raspberry. In general, fall bearing cultivars require less chilling and exhibit earlier flowering than summer bearing cultivars (Dale et al. 2005) The earlier bloom in ‘Heritage’ resulted in an earlier fruit harvest period compared with ‘Tulameen’. The longer fruit harvest season in ‘Heritag e’ compared to ‘Tulameen’ was also observed in previous work (Daubeny and Anderson, 1991; Keep, 1988) and likely reflects genotypic differences. Thus, even though the present experiment relied on

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30 floricane production in both ‘Her itage’ and ‘Tulameen’, the cultivar difference in fruit harvest period were still evident. Although fruit weight in ‘Tulameen’ was almost twice that in ‘Her itage’, fruit fresh weight of both cultivars appears to be lowe r in our experiment compared with other work. Fruit fresh weight for ‘Tulameen’ rang ed from 2.9 g/fruit in North Italy (Giongo et al. 2004) to 5.4 g/fruit in Canada (Daube ny and Anderson, 1991). Fruit weight in ‘Heritage’ averaged 1.9 g/fruit in the Northeastern U.S. (Hoover at al ., 1988) and 1.9 to 2.8 g/fruit in the Southeastern U.S. (Myers, 1993); i.e. at least 1.0 g gr eater than fruits in the present experiment (1.7 g/fruit). The higher yield on ‘Tulameen’ compared w ith ‘Heritage’ canes was the result of differences in fruit size rather than fruit number per cane. However, even though ‘Tulameen’ yielded better than ‘Heritage’ in this experiment, both cultivars remained below the yield reported for them in other experiments. In previous work, ‘Tulameen’ averaged about 185 fruits and ~ 1.0 kg per cane (Daubeny and Anderson, 1991), which is almost twice the number of fruits and more th an three times the yield per cane obtained in our experiment. Containerized ‘Heritage’ can es averaged ~110 fruit per cane and 2.5 g per fruit, for a total yield of 280 g per cane (Dale et al. 2001). In this experiment, ‘Heritage’ yielded 106 fruits per cane for a total yield of 170 g per cane. This decreased yield per cane compared with previously reported data fo r these cultivars may be the result of carbohydrate depletion in the canes af ter the severe root pruning they received prior to being shipped from the nursery. Pr evious experiments in apple (Schupp and Ferree, 1987; 1989), grape (Ferree et al. 1999; Lee and Kang, 1997) and sweet cherry (Webster et al. 1997) found a negative impact of root pruning on fruit size. Furthermore,

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31 root carbohydrates in ras pberry support early floricane growth (Whitney, 1982; Fernandez and Pritts, 1994). In raspberry, flow er differentiation is st ill occurring in basal buds on the cane during budbreak (Williams, 1960: Huang and Lei, 1998) and carbohydrates are crucial fo r flower formation in Sinapsis alba (Bodson and Outlaw, 1985), blueberry (Darnell, 1991) and pers immon (Ooshiro and Anma 1998). The elimination of part of the root for shippi ng dormant long canes might decrease the root carbohydrate pool and therefore de crease yield in raspberry. In general, fruit quality in ‘Heritage’ wa s lower than fruit quality in ‘Tulameen’, although both cultivars yielded fruits with si milar or higher quality (as measured by TA and SSC) than fruits obtained by previ ous researchers (Daubeny and Anderson, 1991; Perkins-Veazie and Nonnecke, 1992). The grea ter acidity and lower SSC in ‘Heritage’ fruits compared with ‘Tulameen’ is supported by Daubeny et al. (1992), who concluded that ‘Heritage’ fruit quality was lower th an in many summer-bearing cultivars. Both cultivars however, had SSC values above 8.0, the minimum proposed for raspberry by Kader (2001). ‘Tulameen’ fruits approach ed the 0.8% maximum TA proposed by the same author; but ‘Heritage’ fruits surp assed this maximum. Perkins-Veazie and Nonnecke, (1992) reported that ‘Heritage’ fr uits can reach 10.5% SSC and 1.2 % TA at the dark-red stage of maturity. In-row Spacing The increased bloom period at 50 cm in-row compared with 25 cm in-row spacing may be due to decreased light competition a nd therefore increased carbohydrate synthesis and availability for flowering. This is mo re likely than competition for water and nutrients, since watering and fertilization we re made on a plant basi s instead of an area basis. Similarly, the decrease in flower number per cane at 25 cm compared to 50 cm in-

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32 row spacing may also be explained by light competition. Jansen (1997) found an increase in strawberry flower number when plants were spaced at lower densities (33 to 43 plants/m2) compared to higher dens ities (66 to 87 plants/m2). Similarly, Menzel and Simpson (1989) found that continuous or inte rmittent shade in passion fruit during vine growth reduced flower number. The shading eff ect may be even more important in plants like raspberry, where cane yiel d depends on the amount of av ailable assimilates per node (Crandall et al. 1974) and the main source of carbohydrates for the developing fruit are the nearest leaves in the same lateral (Prive et al. 1994; Fernandez and Pritts, 1993). In the present experiment, the lower flower numbe r in canes spaced at 25 compared with 50 cm in-row may be the result of more intense shading and a resultant decrease in assimilate availability. The fruit development period was not aff ected by in-row spacing, suggesting that light was not limiting fruit development in ou r experiment. Temperature was found to be the environmental factor with the stronge st effect on fruit ripening of blackberry (Jennings 1979) and cloudberry (Kortesharju, 1993), and this may be true in raspberry also. If so, there would have been no in-ro w spacing effect on the fruit development period, since temperatures in side the tunnel were the sa me for both in-row spacing. The negative relationship between yield per cane and plant density has been reported previously. Oliveira et al. (2004) obtained lower yields as cane density increased from 8 to 32 canes per meter row in the fall-bearing ‘Autumn B liss’ red raspberry. Similarly, yield per cane and cane density we re negatively correlated in four summerbearing red raspberry cultivar s (Sullivan and Evans, 1992).

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33 The decreased cane yield observed at the de nser spacing in the present experiment was due to a decrease in fl ower number per cane and cons equently a decrease in fruit number per cane, as neither fruit set nor fru it size were affected by in-row spacing. This differs from previous work in which fruit se t decreased as cane density of red raspberry increased from 6 to 12 canes per hill (Crandall et al. 1974); however, the authors did not report the effect of cane density on flower number per cane. In our experiment, the decreased flower number per cane at the 25 vs the 50 cm in-row spacing would have resulted in less competition for carbohydrates during fruit set and development, resulting in similar fruit set percentages at the two spacings even though fr uit number per cane was greater at the 50 cm spacing. Despite the lowe r yields per cane obt ained at 25 vs 50 cm in-row spacing, the closer spacing would in crease the number of canes per area and potentially increase yields per hectare. Th ese results coincide with Myers (1993) who found an increase in yield per area by decrea sing in-row spacing from 100 to 25 cm in ‘Heritage’ raspberry. In general, in-row spacing did not negatively affect fruit quality in our experiment, as fruit soluble solids were above the minimu m of 8% and fruit acid ities were near the maximum of 0.8% proposed by Kader (2001) for raspberry. Fruit quality is related to light interception by the canopy of red raspberry (Palmer et al. 1987). Vanden Heuvel et al. (2000) found a decrease in fruit soluble solid s when red raspberry canes were trellised in a horizontal system compared to those fruits from canes in a v-trellis system, the latter allowing more light to reach the fruiting laterals. Even though the authors did not measure the light penetration into the canopy, they suggested that the effect of the trellis system on fruit quality might be mediated by the amount of light reaching the fruit. In our

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34 experiment, a decrease in light intercep tion by fruiting laterals and a concomitant decrease in the availability of assimilate s for fruit development may explain the lower fruit soluble solids in canes spaced at 25 cm compared with canes spaced at 50 cm. Fruit titratable acidity remained unaffect ed by cane density in our experiment. Similarly, Vanden Heuvel et al. (2000) found no effect of tr ellising on titrat able acidity, suggesting no effect of light interception on fruit acidity. Conclusion This experiment demonstrated that an a nnual winter raspberry production system in subtropical climates is feasible; however, th e economics of this system need to be analyzed. ‘Tulameen’ had higher yields and bett er overall fruit quality than ‘Heritage’. These characteristics in ‘Tulameen’, added to its shorter fruit harv est period, makes this cultivar more suited for this cropping system. Additionally, higher yields can be achieved by increasing the plant density in the tunnel without affecting fruit quality. The yield obtained in this experiment wa s lower than those re ported previously for these cultivars (Daubeny and Anderson, 1991; Myers, 1993; Dale et al. 2001). Optimizing plant performance in this system will be crucial for if it is economically viable. Bumble bees should be used in or der to improve pollina tion (Schloemann, 2001) as 90-95% of pollination in raspberry result s from bee activity (Galletta and Violette, 1989). Additionally, more research is needed on irrigation and fertil ization, as well as pest and disease control in this new system. The relative yield decrease in both cultivars observed in this experiment may be due to root loss and consequently loss of root stored carbohydrates when canes were removed from the nursery. This type of root pruning is inevitable in an annual system

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35 such as this one, and further re search is needed to determine its possible effects in sourcesink relations and plant yield. 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 2/9 2/16 2/23 3/2 3/9 3/163/233/304/6 DateFlowers per Cane Heritage Tulameen Days After Planting 43 50 57 64 71 78 85 92 99 A 0.0 5.0 10.0 15.0 20.0 25.0 2/9 2/162/233/2 3/9 3/163/23 3/304/6 DateFlowers per cane 25 cm 50 cm Days After Planting 43 50 57 64 71 78 85 92 99 B Figure 3-1. Flowering in ‘Her itage’ and ‘Tulameen’ red ra spberry planted at in-row spacings of 25 (A) or 50 cm (B) in a winter production in North Florida (2002). Arrows show 50% of cumulative flowering. (n=7).

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36 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 2/283/7 3/14 3/21 3/28 4/4 4/114/184/255/2 5/9 5/16 DateFruits per cane Heritage Tulameen 62 69 76 83 90 97 104 111 118 125 132 139 Days After Planting A 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 2/28 3/7 3/143/213/28 4/4 4/11 4/18 4/255/2 5/9 5/16 DateFruits per cane 25 cm 50 cm 62 69 76 83 90 97 104 111 118 125 132 139 Days After Planting B Figure 3-2. Fruiting in ‘Heritage’ and ‘T ulameen’ red raspberry planted at in-row spacings of 25 (A) or 50 cm (B) in a winter production in North Florida (2002). Arrows show 50% of cumulative flowering. (n=7)

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37 Table 3-1. Flowering of Herit age and Tulameen red raspberry as affected by in-row spacings in a winter production sy stem in North Florida. (n=7) z DAP= Days after planting y Means in the same factor are differe nt by t-test at th e indicated P-value Table 3-2. Fruit harvest period in Heritage and Tulameen red as affected by in-row spacings in a winter production sy stem in North Florida. (n=7) Factor Beginning of fruiting (DAPz) 50% fruiting (DAP) End of fruiting (DAP) Fruit Development Periody (days) Fruiting Period (days) Cultivar Heritage 74.9x 116.1 139.4 34.6 64.4 Tulameen 87.1 111.3 135.9 30.1 48.8 P -value <0.0001 0.001 0.0003 0.0006 <0.0001 In-row spacing 25 cm 82.4 112.4 136.4 32.0 54.1 50 cm 79.6 115.0 138.8 32.7 59.1 P -value 0.073 0.06 0.007 0.51 0.01 z Fruit development period was estimated as the time between peak bloom and peak fruit harvest y DAP= Days after planting x Means in the same factor are differe nt by t-test at th e indicated P-value Factor Beginning of bloom (DAPz) 50% bloom (DAP) End of bloom (DAP) Bloom period (days) Cultivar Heritage 43.0y 81.6 100.4 57.4 Tulameen 50.6 81.1 99.9 49.2 P -value <0.0001 0.52 0.31 <0.0001 In-row spacing 25 cm 47.8 80.4 99.3 51.5 50 cm 45.9 82.3 101.0 55.1 P -value 0.12 0.01 0.006 0.007

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38 Table 3-3. Reproductive development in Her itage and Tulameen red raspberry as affected by in-row spacing in a winter production system in North Florida. (n=7) y Means in the same factor are differe nt by t-test at th e indicated P-value Table 3-4 Fruit quality in Heritage and T ulameen red raspberry as affected by in-row spacing in a winter production sy stem in North Florida. (n=7) April 9 April 16 Factor Soluble solids (%) Citric acid (%) SSC/TTA Soluble solids (%) Citric acid (%) SSC/TTA Cultivar Heritage 13.78z 1.20 11.4 12.37 1.08 11.5 Tulameen 14.10 0.85 11.6 13.41 0.82 17.8 P -value 0.20 <0.000 1 <0.0001 <0.0001 <0.0001 0.008 In-row spacing 25 cm 13.64 1.05 13.6 12.60 0.99 13.1 50 cm 14.21 1.01 14.5 13.17 0.91 16.2 P -value 0.06 0.16 0.04 0.007 0.16 0.16 y Means in the same factor are different by t-test at the indicated P-value Factor Flowers per cane Fruits per cane Fruit set (%) Yield per cane (g) Fruit size (g) Yield per area (kg/ha) Cultivar Heritage 105.9z 97.7 91.1 169.5 1.74 2583.62 Tulameen 114.6 100.41 91.4 309.8 3.10 4875.96 P -value 0.46 0.81 0.91 0.0001 <0.0001 <0.0001 In-row spacing 25 cm 91.2 79.63 89.7 192.0 2.39 4267.46 50 cm 129.4 118.5 92.7 287.3 2.45 3192.12 P -value 0.004 0.004 0.23 0.004 0.50 0.01

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39 CHAPTER 4 EFFECT OF INTENSITY AND TIMING OF GIRDLING ON WINTER RASPBERRY (Rubus idaeus L.) PRODUCTION Yield in horticultural crops is a function of number of pl ants per area, fruit number per plant and fruit size. Fru it number per plant is a functi on of flower bud number and fruit set. Carbohydrate content influences flower bud initiation and fruit set in many plants. In Sinapsis alba, sucrose accumulation in the meristem appears essential for floral induction (Bodson and Outlaw, 1985). A similar effect was found in some cultivars of rabbiteye blueberry (Vaccinium ashei), where the mobilization of 14C-labeled carbohydrates from leaves to nodes increased under short day compared with long day conditions (Darnell, 1991). Short days also in creased flower bud initiation compared with long days. The increase in carbon mobilization to nodes occurred early in the short day cycle, and may be a requirement for enhanced flower bud initiation in blueberry. Ooshiro and Anma (1998) found similar results for persimmon, where they reported a high correlation between leaf soluble sugars and the beginning of flower bud initiation (FBI). They also found a high correlation between flower number and N content in young wood. They concluded that carbohydrat e content during FBI and le af N content during flower bud differentiation (FBD) are important factor s for the number and quality of flowers in persimmon. However, even though these experi ments, which are intended to explain the relationship between carbohydrate status in the plant and flow er initiation, have found a correlation between these two factors, the question remains as to whether carbohydrates

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40 are playing a key role in FBI or whether th e observed increases are also a response to some other factor induc ing flowering. Spann et al. (2004), working with V. corymbosum interspecific hybrid (southern highbush blue berry) growing under both inductive (short day) and non inductive (long day) conditions found greater FBI under inductive short day conditions, but there was no correlat ion between carbohydrat e concentration and FBI. This suggests that carbohydrates do not pl ay a primary role in FBI in blueberry. Havelange et al. (2000) found a relationship between FBI in S. alba and concurrent shoot to root movement of carbohydrate and root to shoot movement of cytokinin They concluded that both carbohydrate and cytokinin movement were essential for FBI in that species. The effect of carbohydrate status on fruit set has been documented in Citrus, where fruit set is strongly decreased by reducti ons in carbohydrate availability (Iglesias et al., 2003). In citrus, girdling has been used comm ercially in order to increase carbohydrate availability for fruit development and avoid early fruitlet drop (Goren et al., 2004). Crandall et al. (1974) also found a relationship between increased fruit set and carbohydrate accumulation in nodes of red ra spberry. On the other hand, carbohydrate concentration was not correlate d with fruit set and initial fruit growth in strawberry (Darnell and Martin, 1988) or with fruit set and yield in cranberry (Roper et al., 1995). Fruit size is also influenced by carbohydrat e availability. In rabbiteye blueberry, the availability of both stored and current carbohydrates were impo rtant for fruit size (Darnell and Birkhold, 1996). Larger fruits were harvested in the cultivar Bonita than in the cultivar Climax. Apparent ly the relative reduction in fruit size in ‘Climax’, where flower budbreak precedes vegetative budbreak, wa s the result of depletion in stored

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41 carbohydrates early in the fruit developm ent period and late current carbohydrate availability. This was not the case for ‘Bon ita’, where flower budbreak and vegetative budbreak were concomitant. Similarly, Maust et al. (2000) found an increase in fruit size when ‘Sharpblue’ blueberries (V. corymbosum hybrid) were grown under CO2 enrichment during the previous fall, re lative to plants grown in ambient CO2 concentrations. However, the authors did not observe the same tendency in similarly grown plants of the cultivar Misty. Either the synthesis of assimilates in plants under CO2 enrichment during the previous fa ll was not sufficient to increase fruit size in ‘Misty’ or the fruit size in this cultivar relies more on current than on stored carbohydrate. Carbohydrate dynamics in raspberry follow a similar pattern as in other perennial crops. In raspberry, roots and primocanes ar e responsible for assimilate storage during winter (Crandall, 1995); At th e beginning of the season, when laterals, new primocanes, and roots start growing simultaneously, th e demand for stored carbohydrates increases (Fernandez and Pritts, 1994). During this stage, there is a continuous decrease in root dry weight, which stops only when floricane ne t photosynthetic rate increases and the floricane lateral leaves become sources. At that point, root dry weight begins to increase (Fernandez and Pritts, 1993;1994). The new primocane dry weight also increases continuously until mid fruiting, at which point dry weight in primocanes remains stable, before increasing at the end of the se ason (Fernandez and Pritts, 1993). During the winter, root dry weight decrease slightly, probably due to respiration, then decrease more dramatically at the beginning of the fo llowing season (Whitney, 1982; Fernandez and Pritts, 1994).

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42 The importance of root carbohydrates for plan t yield in raspberry has not been fully investigated. In perennial fru it crops, carbon stored in roots du ring the fall is essential for yield the following season (Teng et al., 1999). In red raspberry, fruit development and consequently cane yield rely on current car bohydrates from the nearest photosynthetic leaves (Fernandez and Pritts, 1993; Prive et. al., 1994); however, root stored carbohydrates are important for yield the fo llowing year when current assimilate availability is inadequate (Fernandez and Pritts, 1996). The question remains whether root carbohydrates during budbr eak are important for raspberry cane yield. On the other hand, if we consider that raspberry shoot gr owth coincides with root growth (Atkinson, 1973), then we also have to consider the question whether cane carbohydrates are important for root growth. The present experiment tested the hypothesi s that root carbohydrates are mobilized to the cane during budbreak and are important for current cane fruit yield. The objective was to assess the effect of time and intens ity of floricane gird ling on cane fruit yield components and dry weight distribution. Materials and Methods This experiment was conducted in a polye thylene tunnel at the University of Florida in Gainesville, FL (29.69N and 82.35W). The tunnel, bed system, trellising system, heating and ventilation were previously described in chapter 3. Substrate in this experiment was a mixture of perlite: peat: coir: pinebark (48: 12:15:25). Plant Material Dormant bare-root long cane raspberry cu ltivars ‘Tulameen’ and ‘Willamette’ were purchased in fall 2002 from nurseries in the Northwest US. Canes arrived in Gainesville on 25 Oct. 2002 and were grouped, roots wrappe d in wet cypress sawdust as described

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43 previously (Chapter 3), and canes were pl aced in a darkened walk-in cooler at 7o C. Canes were planted in the tunnel on 18 D ec. 2002, after 1320 hours of chilling. Both ‘Tulameen’ and ‘Willamette’ are summ er bearing cultivars. ‘Willamette’ has lower yields than ‘Tulameen’ due to smaller fr uit size, but it has an earlier harvest season (Pacific Agri-food Research Center [PARC], 2003). Plant Growth Canes were planted in the beds at 50 cm in-row distance, with between-row distance of 180 cm. The trellis system was esta blished as previously described in Chapter 3. In order to attain better control of root media moisture and avoid root rot (Phytophthora spp.), the drip irrigation system was not used during this experiment; instead, canes were hand-watered as needed at a rate of 2 L per cane. Plants were fertilized with 20-8.8-16.6 N:P:K (J.R. Pete rs, Inc. Allentown, Pe nn.) in the irrigation water at a rate of 0.6 g of nitrogen (N) per plant. All but three pr imocanes were removed once they reached 20 to 30 cm length. The re maining three primocanes were allowed to grow during the whole season; thus, all plants containe d three primocanes. Pruned primocanes were dried and dry weights obtained. As in the previous experiment (Chapter 3), Captan 50WP (5.6 kgha-1) was sprayed for control of Botrytis every 7 to 10 days through winter and spring. Flowers and fruits per cane were recorded every other day from the beginning of bloom and fruit harvest, respectively. Fruits were harvested at pink color (Perkins-Veazie and Nonnecke, 1992) to avoid drupelets loss by crumbling. Fruits were weighed and dried at 80o C until constant weight a nd dry weights were recorded Fruits harvested at the peak of harvest, estima ted as 30 days after the peak of bloom, were kept frozen at -21o C until fruit quality analysis. After fruit harvest, plants were divided into roots, canes, laterals and primocanes and fresh and dry weight s were obtained. Fruit

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44 quality analysis was conducted as in the previous experiment (Chapter 3). Daily temperatures were recorded as explained in Chapter 3. Girdling Three intensities of flori cane girdling (none, 75%, and 100%) at two dates were tested on each of the two va rieties in this experiment. Complete (100% ) girdling was done at 10 cm above the media level by removi ng a strip of 3 mm of cortex (epidermis, cortex and phloem) around the entire circum ference of the cane with a sharp knife. Incomplete (75%) girdling was done in a si milar way except that the strip of cortex removed encircled ~75% of the cane circumfere nce. Non-girdled canes were used as the control. Early girdling was done before bloom (6 Feb. 2003 for both cultivars) and late girdling was done at the peak of fruit harv est (24 Mar. 2003 for ‘Willamette’ and 2 Apr. 2003 for ‘Tulameen’). Captan 50WP (0.5 g/L) was sprayed on the girdling zone the same day of girdling. Experimental Design Three factors were used in this experime nt: variety with two levels (‘Willamette’ and ‘Tulameen’), girdling intensity with th ree levels (no girdling, complete [100%] girdling and incomplete [75%] girdling) and girdling time with two levels (early and late). The resulting ten treat ments were arranged in the tunnel in a completely randomized design (CRD). There were six repl ications per treatment and one plant was considered as the experimental unit. For statistical analysis, two treatments were discarded (early a nd late 100% girdling of ‘Willamette’), as these plants died as a result of the treatment. When analyzing data combining cultivars, the two 100% girdling treatments in ‘Tulameen’ were also discarded. Late girdling plants were not anal yzed in flowering and fruiting time, as these

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45 treatments were applied after flowering and fruiting began. Analyzing cultivars together for flowering and fruiting time became a twoway 2x2 factorial with two varieties and two girdling levels (non-girdled control and early, 75% girdled). Analyzing these same variables by cultivar became a one-way co mplete randomized design (CRD) with three treatments (control, 100% gi rdling and 75% girdling). Yiel d components, dry weight allocation and fruit quality data for ‘T ulameen’ were analyzed as a two-way 2x2 incomplete factorial (2x2 factorial with a c ontrol) with two levels of girdling intensity and two levels of girdling time plus the non-girdled control. Yi eld components and dry weight allocation for ‘Willamette’ were analyzed as a one-way CRD with three treatments (non-girdled contro l, early and late 75% girdlin g). Finally, analyzing these same variables for both cultivars together became a two-way 2x3 factorial with two cultivars and three girdling tr eatments (non-girdled control, early and late 75% girdling). Data were analyzed using the General Linear Model Procedure in SAS (SAS institute Inc., Cary, NC, USA. 2002). Results Girdling intensity had a dramatic effect on ‘Willamette’, where both early and late 100% girdled canes wilted and died during th e fruit harvest season. ‘Willamette’ canes subjected to 75% girdling a nd all ‘Tulameen’ canes grew and fruited without problem during the season. In order to avoid bias in the inferences, both 100% girdled treatments in ‘Willamette’ were removed from data analysis. Flowering The effect of girdling time on bloom could not be assessed in this experiment as late girdling was done 96 days after planting (DAP) in ‘Willamette’ and 115 DAP in ‘Tulameen’, 11 and 25 days after peak of bloo m respectively (Table 4-1). At the time of

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46 late girdling, more than 50% (‘Willamette’) and 80% (‘‘Tulameen’’) of the flower buds had opened in the non-girdled canes. No difference in bloom period was observed between ‘Willamette’ and ‘Tulameen’; however, ‘Willamette’ started blooming about 10 days earlier than ‘Tulameen’ (Table 4-1). Girdled canes reac hed 50% bloom earlier than non-girdled canes, but there was no effect of gird ling on the length of the bloom period. In general, girdling had little affect on bloom period in ‘Tulameen’ or in ‘Willamette’ when analyzed separately (Tables 4-2, 4-3). Bloom period was similar for both cultivars, except for a delay of 3 to 4 days in end of bloom in ‘Tulameen’ girdled plants compared with the control (p=0.02), which resulted in a slightly longer bloom period for 100% girdled canes (p=0.09). Fruiting Fruit harvest began ~5 days earlier in ‘Willamette’ compared with ‘Tulameen’, but the fruit harvest period was significantly shorter in ‘Tulameen’ than in ‘Willamette’ (Table 4-4) Fruit harvest time was not affected by 75% girdling (Table 4-4). When ‘Tulameen’ was analyzed separately, fruit harvest of 100% girdled canes was completed about 17 days later than non-girdled can es (p=0.09) (Table 4-5); how ever, there was no difference between treatments in the length of the fruit harvest period. Similarly, ‘Willamette’ was not affected by girdling except for a decrease in the time to reach 50% of fruit harvest and a slight decrease in the length of the fruit harvest peri od (p=0.08) in 100% girdled canes compared with the non-gi rdled controls (Table 4-6).

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47 Yield Components ‘Tulameen’ had more flowers per cane than ‘Willamette’ (115 vs 89 respectively); however, ‘Willamette’ had significantly higher fr uit set, resulting in a slightly greater, although not statistically diffe rent, fruit number per cane (Table 4-7). Fruit size was significantly larger in ‘Willamette’ compared with ‘Tulameen’; this, combined with the small difference in fruit number in ‘Willa mette’, resulted in higher yields for ‘Willamette’ compared with ‘Tulameen’. In general, girdling did not affect ‘Tul ameen’ yield components. Girdling intensity reduced flower number per cane in 100% gird led treatments comp ared with the nongirdled controls (Table 4-8). Early girdling decreased fruit number per cane (p=0.08), resulting in lower yields in early-girdled canes compared with the control (p=0.09). Girdling had no effect on yield component s of ‘Willamette’ except for a slight (p=0.07) reduction in flower number in early -girdled canes compared with the control (Table 4-9). Dry Weight Allocation At the end of the season, there was no diffe rence in dry weight partitioning between cultivars, except for the dry weight accumu lated in fruit (Table 4-10). ‘Willamette’ allocated more dry weight to fruits than ‘Tulameen’ (26.1 vs 13.7 g respectively) during the growing season; however, this difference did not affect the fi nal total plant dry weight. Similarly, girdling time had no effect on dry weight alloca tion compared to the control (Table 4-10). When yield components in ‘Tulameen’ were analyzed separately from ‘Willamette’, girdling intensity affected dry weight allocation to roots. Dry weight accumulation in roots of 100% girdled ‘Tulam een’ was significantly decreased compared

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48 with non-girdled canes (Table 4-11). Dry weight allocation in ‘Tulameen’ was not affected by girdling time. Similarly, girdli ng did not affect dry weight allocation in ‘Willamette’, except for a slight reduction in dry weight allocated to laterals in earlygirdled canes compared with late-girdled a nd non girdled control canes (p=0.09) (Table 4-12). Fruit Quality Fruit quality was analyzed only for ‘Tul ameen’ fruits. Incomplete (75%) girdling increased fruit soluble solids (P=0.07) compar ed with the non-gird led control and 100% girdled canes (Table 4-13). Similarly, fru its from late girdled canes had significantly greater soluble solids compared with fruits from non girdled control canes (13.2 vs 12.2 %, respectively). Girdling before bud break had no effect on fruit soluble solids. Discussion Bloom and Fruiting Period In general, girdling did not affect bloom or fruit harvest period in either cultivar. The timing of bloom and fruiting in temper ate crops like raspberry are governed by genotype and environmental factors, partic ularly chilling and heat unit accumulation (Dale et al., 2001; 2003). Some authors have imp lied the importance of carbohydrates and/or hormones for flower induction /initiation (Darnell, 1991; Havelange et al., 2000; Spann et al., 2004). In raspberry, after flower inducti on conditions have been met in late summer, FBI begins as a continuous process first observed in apical buds of the cane (Williams, 1959). This process continues dow n the cane until budbreak in spring. Early girdling in the present experiment was done at the beginning of budbreak, in early February, when inflorescences in at least th e upper four-fifths of the cane were already initiated (Williams, 1959). Thus, girdling at th is time would be ineffective in altering

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49 bloom time and consequently the fruit harv est period, which are the endpoints of the inflorescence formation in raspberry. Yield Components Both ‘Tulameen’ and ‘Willamette’ fruits were smaller than those reported in previous papers. ‘Tulameen’ is a large fru ited cultivar with fruits up to 5.4 g (Daubeny and Anderson, 1991), while ‘Willamette’ fruit is generally smaller, but larger than was observed in the present experiment (Was hington Red Raspberry Commission [WRRC], 2005). The last winter freeze in the present experiment occurred 12 Feb. 2003 and there was no wild bee activity until late March wh en wildflowers appeared. Thus, pollination efficiency was low and resulted in low fruit set and small crumbly fruits in both cultivars. In general, neither girdling intensity nor girdling time had dramatic effects on yield components in either cultivar. Although 100% girdled canes of ‘Tulameen’ had fewer flowers per cane than the non-gird led controls, the lack of eff ect of the incomplete (75%) girdling indicates that this intensity was in sufficient to interrupt root to shoot phloem communication. These results are similar to pr evious experiments in sour cherry, where removal of a strip up to 50% of the trunk ci rcumference had no effect on growth or productivity (Layne and Flore, 1991). Early girdling slightly decreased flower number per cane in ‘Willamette’, but had no effect in ‘Tulameen’. This difference may be due to earlier flowering in ‘Willamette’ that made this cultivar more responsive than ‘Tulameen’ to early girdling. However, even though the difference in flower number per cane in ‘Tulam een’ was not statistically significant, early girdling treatments decrea sed flowers per cane by 18% compared with the control. Similarly, when both cultivar s were considered to gether, early girdling resulted in 23% less flowers than the cont rol. Although most flower bud initiation and

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50 differentiation in raspberry occurs in late-win ter, individual flower s in the inflorescence continue differentiation until the following spring (Williams, 1959). Similarly, Qingwen and Jinjun (1998) observed continuous inflor escence differentiation in raspberry, with individual flowers continuing differentiation through late Apr il, right befo re anthesis. Although early girdling in the present experiment did not appear to affect the timing of inflorescence differentiation, it may have a ffected individual flow er differentiation in inflorescences in the lower portion of the can e, resulting in fewer flowers in the early girdled canes. Carbohydrates have been implicated as im portant factors for FBI in some crops (Darnell, 1991; Ooshiro and Anma, 1998). Roots appear to be the main source of carbon for the floricanes and primocanes during budbreak in raspberry (F ernandez and Pritts, 1994), which also coincided with the last flush of FBI in the lower cane (Williams, 1959). This suggests that the prevention of carbon mo vement from the root to the floricane during budbreak could result in a reduction in flower number per cane and ultimately yield per cane. However, the role of root-b orne hormones like cytokinin in FBI must not be ignored (Havelange et al., 2000). The lack of effect of late girdling on flower number indicates that either the indi vidual flower formation was comp leted by early spring or that once the lateral leaves became sources of assimilates, the root was no longer important for floricane growth and development. Both fruit set and fruit size are aff ected by carbohydrate av ailability (Crandall et al., 1974; Darnell and Birkhold, 1996; Maust et al.; 2000) and, in this experiment, fruit set and size remained unaffected by girdling. This suggests that on ce the lateral leaves become sources, the assimilates required fo r the developing fruit are provided by the

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51 leaves nearest to the fruit in the fruiti ng lateral (Fernandez an d Pritts, 1993; Prive et al., 1994) and fruit growth apparently does not rely on root carbohydrates (Fernandez and Pritts, 1996). Dry Weight Allocation The effect of girdling on dry weight pa rtitioning in raspberry was minimal, with only a decrease in root dry weight accum ulation in 100% girdled ‘Tulameen’ canes observed. Dry weight allocation in this expe riment was measured only at the end of the fruiting season. Previous research indicates that root carbohydrates are mobilized to floricanes and growing primocanes prim arily during budbreak until these structures become photosynthetically active (Fernand ez and Pritts, 1993). Subsequently, roots become a sink for carbohydrates from florican es and primocanes during the rest of the season (Whitney, 1982; Fernandez and Pritts, 19 93). In the present experiment, roots of girdled canes were the only plant organ deprived of current carbohydrates during the season, and this may explain the decrease in r oot dry weight. Alterna tively, girdling also affects the balance of growth regulators like IAA above and below the girdle (Dan et al., 1985). The reduction of translocation of shoot-s ynthesized auxins to the root may also play a role in the decrease in root dry weight of girdled canes. Although girdling intensity decreased onl y root dry weight accumulation in ‘Tulameen’, there was a general tendency to wards decreased dry weight accumulation in other plant organs due the girdling. This re sponse, added to the si gnificant reduction in root dry weight in 100% girdled canes, resulte d in less total dry weight gain in girdled plants compared with control plants at the e nd of the experiment. This reduction in total plant growth as a result of girdling might be re lated to alterations in movement of growth factors other than carbohydrat es, as shoot growth does not rely on root carbohydrates

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52 once budbreak has occurred (Fernandez and Pritts, 1994). Cutting and Lyne (1993) found that girdled peach trees exhibited reduced s hoot growth, and this was correlated with decreases in cytokinin an d gibberellin concentrations in the xylem sap. Fruit Quality Increases in fruit soluble solids have been reported in girdled peach (El-Sherbini, 1992; Taylor, 2004), grape (Dhill on and Bindra, 1999; Nikolaou et al., 2003), Clementine mandarin (Yesiloglu et al., 2000) and apple (Arakawa et al., 1998) compared with nongirdled controls. In the present experiment, in creases in soluble solids were observed in the 75% girdling but not in the 100% girdli ng treatments. High fruit-to-leaf ratios can decrease fruit soluble solids and reduce fruit size (Prange and DeEll, 1997). In the present experiment, 100% girdled canes had a significantly higher fru it:leaf FW ratio compared with both the 75% girdled and control canes. Thus, there would be greater competition for assimilates among fruits in the 100% gird led canes, resulting in a decrease in fruit soluble solids. Similarly, Onguso et al. (2004) found an increase in peach fruit soluble solids in partially girdled trees co mpared with nongirdled controls. In this experiment, the timing of girdli ng had a significant effect on fruit soluble solids, with the highest soluble solids observe d in late girdled can es. El-Sherbini (1992) and Chanana and Beri (2004) found increases in fruit soluble solids by girdling peach branches from bloom through stages I and II of fruit development; however, they found no effect if girdling was done during stage III. In our experiment, late girdling was done when fruits harvested for quality analysis were in stage III of fruit development. This is the stage when 85% of fruit sugar accumula tion and fruit growth occur in raspberry (Crandall, 1995). Thus, raspberry fruit sugar accumulation may be more sensitive to girdling during stage III of development than has been found in other fruits.

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53 The effect of girdling can be temporary (Goren et al., 2004) unless the girdled zone is maintained and blockage of phloem transloc ation continues, in which case a permanent effect during the growing s eason can be achieved (Prive et al., 1994). In the present experiment, the girdled zone was allowe d to grow back, thus allowing phloem translocation to resume later in the growing season. The lower fruit soluble solids observed in the early girdling compared with the late girdling might result from the healing of the ring during ear ly fruit growth and the resumption of assimilate translocation from the floricane to the root during this time. Girdling at the peak of fruit harvest, when the most rapid accumulation of carbohydrates into the fruit is occurring (Fernandez and Pritts, 1993; Darnell a nd Birkhold, 1996), woul d prevent carbohydrate translocation from floricanes to roots and therefore increasing assimilate availability for fruits. Fruit soluble solids in this experiment were above the minimum recommended for raspberry; however, fruit ci tric acid was about three ti mes higher than the maximum proposed for this crop (Kader, 2001). In this experiment, the drip irrigation system was not used as explained in Chapter 3 and pl ants were hand-watered every other day. Apparently as a result from the daily change in soil moisture, crumbly fruit were frequent in this experiment and harvest had to be done at pink or red fruit color and not at dark red color as explained in Chapter 3. Harvesting fru its at unripe stages in this experiment was probably the cause for higher citric acid leve ls found in these fruits compared to those from Chapter 3. Conclusion Girdling alters physiological processes that are in fluenced by carbohydrate and hormonal status. The effect of girdling befo re bloom on flower number per cane suggests

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54 the importance of the root in the late FBI pro cess in the raspberry floricanes. On the other hand, the lack of a girdling effect on fruit development suggests roots may have only a minor role in this process. However, it is not clear whether ca rbohydrates, hormones or their combination are playing the ma in role in this girdling effect. The reduction of final root dry weight and the ineffectiveness of girdling in altering floricane dry weight accumulation indicates th at floricanes are an important source of carbon for root growth, rather than the other way around. Primocane growth does not appear to re ly on floricanes, but the importance of primocanes in root and floricane growth needs to be determined. Table 4-1. Flowering of Willamette and Tulameen red raspberry as affected by 75% girdling in a winter production sy stem in North Florida (n=6). Factor Beginning of bloom (DAP)z 50% bloom (DAP) End of bloom (DAP) Bloom period length (days) Cultivar Willamette 55.5y 82.0 140.8 85.3 Tulameen 66.3 90.2 144.8 78.5 P-value <0.0001 0.15 0.29 0.13 Girdlingx Control 61.5 92.0 142.5 81.0 Girdled 60.3 80.2 143.2 82.8 P-value 0.55 0.04 0.86 0.68 z DAP= Days after planting yMeans of the same factor with in the same column are differe nt by t-test at the indicated P -value. x Girdling was done on 6 Feb. 2003 by removing a strip of bark encircling 75% of the cane circumference at 10cm above the media level. Table 4-2. Flowering of Tulameen red raspbe rry as affected by gi rdling intensity in a winter production system in North Florida (n=6). Girdling intensityz Beginning of bloom (DAP)y 50% bloom (DAP) End of bloom (DAP) Bloom period length (days) Control 67.0x 89.7 143.0b 76.0b 75% girdling 65.7 90.7 146.7a 81.0ab 100% girdling 60.3 91.7 146.3a 86.0a P-value 0.14 0.96 0.02 0.09 zGirdling was done on 6 Feb. 2003 at 10 cm above media level. yDAP= Days after planting xLSMean separation by Tukey at the indicated P-value

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55 Table 4-3. Flowering of Willamette red raspbe rry as affected by girdling intensity in a winter production system in North Florida (n=6). Girdling intensityz Beginning of bloom (DAP)y 50% bloom (DAP) End of bloom(DAP) Bloom period length (days) Control 56.0x 94.3 142.0 86.0 75% girdling 55.0 69.7 139.7 84.7 100% girdling 58.7 91.3 120.3 61.7 P-value 0.47 0.22 0.16 0.13 zGirdling was done on 6 Feb. 2003 at 10 cm above media level. y DAP= Days after planting xLSMean separation by Tukey at the indicated P-value Table 4-4. Fruit harvest of Willamette and Tulameen red raspberry as affected by girdling in a winter production sy stem in North Florida (n=6). Factor Beginning of fruit harvest (DAP)z 50% fruit harvest (DAP) End of fruit harvest (DAP) Fruit harvest period (days) Cultivar Willamette 89.5y 115.8 164.0 74.5 Tulameen 94.4 122.4 155.5 56.1 P-value <0.0001 0.31 0.26 0.02 Girdlingx Control 94.4 127.2 158.0 83.5 Girdled 94.5 111.1 161.6 67.1 P-value 0.81 0.02 0.62 0.64 zDAP= Days after planting yMeans of the same factor with in the same column are differe nt by t-test at the indicated P -value. xGirdling was done on 6 Feb. 2003 by removing a strip of bark encircling 75% of the cane circumference at 10cm above the media level. Table 4-5. Fruit harvest of Tulameen red rasp berry as affected by girdling intensity in a winter production system in North Florida (n=6). Girdling intensityz Beginning of fruit harvest (DAP)y 50% of fruit harvest (DAP) End of fruit harvest (DAP) Fruit harvest period length (days) Control 98.8x 126.4 151.4bx 52.6 75% girdling 100.0 118.5 159.7b 59.7 100% girdling 97.6 117.7 167.7a 70.0 P-value 0.36 0.49 0.09 0.11 zGirdling was done on 6 Feb. 2003 at 10 cm above media level. yDAP= Days after planting xLSMean separation by Tukey at the indicated P-value

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56 Table 4-6. Fruit harvest of ‘Willamette’ red ra spberry as affected by girdling intensity in a winter production system in North Florida (n=6_). Girdling intensityz Beginning of fruit harvest (DAP)y 50% of fruit harvest (DAP) End of fruit harvest (DAP) Fruit harvest period length (days) Control 90.0x 128.0a 164.5a 74.5a 75% girdling 89.0 103.7b 163.5a 74.5a 100% girdling 91.2 104.0b 136.7b 45.5bw P-value 0.38 0.03 0.10 0.08 zGirdling was done on 6 Feb. 2003 at 10 cm above media level. yDAP= Days after planting xLSMean separation by Tukey at the indicated P-value w Fruit harvest period at 100% girdling was significantly reduced as a result of cane mortality in the treatment during the experiment. Table 4-7. Yield components of ‘Willamette’ and ‘Tulameen’ red raspberry as affected by 75% girdling time in a winter produc tion system in North Florida (n=6). Factor Flowers per cane Fruits per cane Fruit set (%) Yield/cane (g) Fruit size (g) Cultivar Willamette 88.6z 64.8 72.9 149.2 2.24 Tulameen 115.1 50.2 40.8 92.6 1.81 P-value 0.07 0.18 0.0001 0.03 0.004 Girdling timey Control 112.9x 65.4 53.2 141.6 2.18 Early 86.7 46.4 60.4 91.2 1.88 Late 106.0 60.6 56.9 129.8 2.02 P-value 0.20 0.23 0.64 0.15 0.13 zMeans of the same factor with in the same column are differe nt by t-test at the indicated P-value. y Early girdling done on 6 Feb 2003 at the beginning of bloom; late girdling done at peak of harvest (22 Mar. 2003 for ‘Willamette’ and 12 Apr. 2003 for ‘Tulameen’). xLSMean separation by Tukey at the indicated P-value

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57 Table 4-8. Yield components for ‘Tulameen’ red raspberry as affect ed by girdling time and intensity in a winter production system in North (n=6). Factor Flowers per cane Fruits per cane Fruit set (%) Yield/cane (g) Fruit size (g) Girdling intensityz Control 106.5ay 39.0 36.6 78.1 2.10 75% girdling 99.2ab 37.1 37.7 67.1 1.75 100% girdling 80.2b 30.5 39.8 55.4 1.80 P-value 0.04 0.15 0.73 0.23 0.71 Girdling timex Control 106.5 39.0a 36.6 78.1a 2.10 Early 87.3 30.7b 37.2 54.2b 1.74 Late 92.0 36.8ab 40.3 68.3ab 1.80 P-value 0.15 0.08 0.62 0.09 0.62 zGirdling was done on 6 Feb. 2003 at 10 cm above media level. yLSMean separation by Tukey at the indicated P-value xEarly girdling done on 6 Feb 2003 at beginnin g of bloom; late girdling done on 12 Apr 2003 at peak of harvest. Table 4-9. Yield components of ‘Willamette’ red raspberry as affected by girdling time in a winter production system in North Florida (n=6). Girdling timez Flowers per cane Fruits per cane Fruit set (%) Yield/cane (g) Fruit size (g) Control 122.8ay 95.2 70.8 210.9 2.25 Early 74.3b 63.5 89.4 132.0 2.10 Late 109.0ab 73.0 68.9 170.0 2.22 P-value 0.07 0.31 0.21 0.26 0.76 zEarly girdling done on 6 Feb 2003 at beginn ing of bloom; late girdling done on 22 March 2003 at peak of harvest. yLSMean separation by Tukey at the indicated P-value

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58 Table 4-10. Dry weight partitioning in ‘W illamette’ and ‘Tulameen’ red raspberry as affected by girding time in a winter pr oduction system in North Florida (n=6) Dry weight (g) Factor Roots Primocanes Floricanes LateralFruits Total Cultivar Willamette 79.3z 191.1 21.3 12.6 26.1 330.0 Tulameen 85.0 172.5 19.6 14.6 13.7 300.2 P-value 0.48 0.23 0.33 0.38 0.004 0.16 Girdling timey Control 87.6x 188.7 19.7 15.9 22.7 330.5 Early 81.9 186.3 20.2 10.2 16.7 320.6 Late 76.9 170.4 21.5 14.7 20.3 294.3 P-value 0.56 0.57 0.62 0.11 0.47 0.36 zMeans of the same factor with in the same column are differe nt by t-test at the indicated P-value. yEarly girdling done on 6 Feb 2003 at beginning of bloom; late girdling done at peak of harvest (22 Mar. 2003 for ‘Willamette ’ and 12 Apr. 2003 for ‘Tulameen’) xLSMean separation by Tukey at the indicated P-value Table 4-11. Dry weight partitioning in ‘Tulam een’ red raspberry as affected by girdling time and intensity in a winter producti on system in North Florida (n=6). Dry weight (g) Factor PrimocaneRoots Floricane Laterals Fruits Total Girdling intensityz Control 181.3y 91.3a 18.3 15.0 14.4a 307.6a 75% girdling 168.2 82.4ab 17.6 14.4 13.3a 296.5ab 100% girdling 139.7 67.0b 21.4 11.1 8.9b 250.1b P-value 0.11 0.04 0.75 0.30 0.06 0.05 Girdling timex Control 181.3 91.3 18.3 15.0 14.4a 307.6 Early 141.7 75.2 20.6 12.3 9.1b 267.7 Late 166.2 73.5 18.3 13.5 13.1ab 280.7 P-value 0.17 0.84 0.90 0.77 0.04 0.45 zGirdling was done on 6 Feb. 2003 at 10 cm above media level. yLSMean separation by Tukey at the indicated P-value xEarly girdling done on 6 Feb 2003 at beginning of bloom; late girdling made on 12 Apr 2003 at peak of harvest.

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59 Table 4-12. Dry weight allocati on pattern in ‘Willamette’ red raspberry as affected by girdling time in a winter production system in North Florida (n=6). Dry weight (g) Girdling timez Primocane Roots Floricane Laterals Fruits Total Control 196.1 83.9 25.5 16.8a y 30.9 353.3 Early 208.0 75.8 20.2 7.6b 23.8 335.4 Late 169.1 78.3 23.6 13.3a 23.4 301.1 P-value 0.29 0.86 0.63 0.09 0.61 0.40 zEarly girdling done on 6 Feb. 2003 at beginnin g of bloom; late girdling done on 22 Mar. 2003 at peak of harvest. yLSMean separation by Tukey at the indicated P-value Table 4-13. Fruit quality in ‘Tulameen’ red raspberry as affected by girdling time and intensity in a winter production system in North-Florida (n=6). Factor level pH Soluble solids (%) Citric acid (%) SSC/TTA Girdling intensityz Control 3.5 12.2by 2.5 4.8 75% girdling 3.6 12.9a 2.6 4.9 100% girdling 3.6 12.2b 2.4 5.1 P-value 0.72 0.10 0.14 0.67 Girdling timex Control 3.5 12.2b 2.5ab 4.8 Early 3.6 11.9b 2.4b 4.9 Late 3.6 13.2a 2.6a 5.1 P-value 0.89 0.006 0.10 0.58 zGirdling was done on 6 Feb. 2003 at 10 cm above media level. yLSMean separation by Tukey at the indicated P-value xEarly girdling done on 6 Feb 2003 at beginning of bloom; late girdling done at peak of harvest (22 Mar. 2003 for ‘Willamette ’ and 12 Apr. 2003 for ’Tulameen’).

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60 CHAPTER 5 EFFECT OF PRIMOCANE REMOVAL AND FLORICANE GIRDLING ON ‘TULAMEEN’ RED RASPBERRY (Rubus idaeus L.) YIELD IN A WINTER PRODUCTION SYSTEM The continuous generation of vegetative canes (primo canes) during the fruiting season in raspberry generates a sink for r oot carbohydrates (Whitney, 1982). For a given primocane, once the new leaves become phot osynthetically competent, this current photosynthate is mobilized to the apices to s upport further vegetative growth, and to roots for storage (Fernandez and Pritts, 1993). It is primarily through carbon mobilization from the primocanes that the root carbohydrat e pool is replenished (Whitney, 1982). Root carbohydrates play an important role in can e yield the following year, as they will support fruit growth (Rangelov et al., 1998) especially when current carbohydrate availability is limited (Fernandez and Pritts, 1996). Since the root carbohydrate st orage pool arises primar ily by carbon translocation from primocanes, photosynthetic biomass of prim ocanes also impacts future cane yield. Red raspberry primocane defoliation between 25%, and 75% in early August decreased cane yield the following year by 26% compared with the non defoliated controls, while total defoliation resulted in a 55% yield decrease (Raworth and Clements, 1996). As with early primocane development, floricane development during budbreak and leaf expansion also depends on root carbohydrat es, as inferred by the reduction in root dry weight during this stage (Whitney, 1982; Fernandez and Pritts, 1994). Once the floricane leaves reach maturity, they re plenish the cane carbo hydrate pool and support growth of apices and developing fruits until th e end of the harvest season, at which time

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61 the floricane carbohydrates are depleted and the cane dies (Whitney, 1982; Fernandez and Pritts, 1993; Prive, 1994). There appears to be substantial comp etition for root carbohydrates between primocanes and floricanes during certain phe nological stages. Primocane removal at the beginning of bloom resulted in yield increases compared with plants where primocanes were maintained during the fruiting seas on (Dalman, 1989), suggesting competition for carbohydrates between primocanes and flori canes. Similary, primocane removal during the growing season of raspberry cv. Glen Clova increased floricane dry weight and fruit yield compared with plants in which primo canes were not removed (Wright and Waister, 1982b). Conversely, the number of primocanes in plants with floricanes removed was significantly greater than in plants with fruiting flori canes (Wright and Waister, 1982a). In the fall-bearing ‘Heritage’, plants w ith all inflorescences removed produced significantly more primocanes compared with plants in which no inflorescences were removed (Vasilakakis and Dana, 1978). Although growth enhancement of prim ocanes by eliminating floricane carbohydrate sinks and vice versa could be expl ained by a competition for light; the plant carbohydrate status should not be ignored si nce roots can act as a source for both floricanes and primocanes during early grow th, and as a sink for carbohydrates from floricanes or primocanes later in the growi ng season. This is supported by previous work that found a decrease in both root carbohydr ate content (Whitney, 1982) and root dry weight (Fernandez and Pritts, 1993) during raspberry budbreak. Late r in the season; however, roots become active sinks for carbohydrates from both floricanes and primocanes (Fernandez and Pritts, 1993).

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62 As the root stored carbohydrates play an important role in flower formation (Bodson and Outlaw, 1985; Darnell, 1991; Ooshiro and Anma 1998) and yield (Fernandez and Pritts, 1994) understanding carbohydrate partitioning patterns among primocanes, floricanes, and roots is crucia l for the successful implementation of an annual winter production system that relies on bare root long-canes, where the root system has been reduced during removal from the nursery rows. The reduction in root biomass would be expected to decrease th e carbohydrate pool in the root and alter carbohydrate dynamics of the plant. The hypothesis of the current experiment is that in an annual winter production system, primocanes contribute to current fl oricane fruit yield by providing assimilates to the root and therefore decreasing root dema nd for assimilates from the floricane. The objective was to determine the effect of girdling and primocane removal on floricane growth and yield components. Materials and Methods This experiment was conducted in a polye thylene tunnel at the University of Florida in Gainesville, FL (29.69N and 82.35 W). The tunnel was described in chapter 3. Both the heating and ventilation systems remained as described in chapter 3. Plant Material Bare-root long canes of the red raspberry cultivar Tulameen were purchased from a commercial nursery in the Northwest U.S. Ca nes arrived in mid-January 2004, and roots were wrapped in wet cypress sawdust as described in chapter 3. Canes were placed in a dark walk-in cooler at 7o C for 1290 hours. After chilling, canes were individually pl anted in black polyethylene containers (OlympianTM C4000. Nursery supplies, Inc. Fairle ss Hills, PA., U.S.A.) filled with a

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63 mixture of coir, perlite and Canadian peat (1 :3:1). Containers were 38 cm high, 40 cm in diameter and 36.7L capacity. Containerized canes were placed in the tunnel the same day of planting. Canes were handwatered as needed with 2L water per pot and fertilized weekly with 20-8.8-16.6 N:P:K water soluble fertilizer (J.R. Peters, Inc. Allentown, Penn.) at a rate of 0.6 g of nitrogen (N) per plant. Leaf diseases were controlled by spraying Captan 50WP every 7 to 10 days at a rate of 5.6 kgha-1. Subdue Maxx was diluted in the ir rigation water at a rate of 60 LL-1 and applied to the potting media once at the beginning of the growing season to control Phytophthora root rot. Plants were scouted for tw o-spotted spider mites and eventually controlled with a commercial mixture of mite predators (Phytoseiulu persimilis, Neoseiulus californicus and Mesoseiulus longipes). Bumblebees (Bombus impatients) were released in the tunnel at the begi nning of bloom to improve pollination. Daily temperatures were recorded as described in Chapter 3. Girdling and Cane Removal On 10 May 2004 (62 days after planting) 24 floricanes were selected for uniformity in height and vigor. Half of the floricanes were girdled by removing a 3-mm strip of cortex with a sharp knife around the cane at 10 cm above the media level. At the same time, primocanes were removed in half of each of the girdled and non-girdled treatment plants. New primocanes in these pl ants were removed continuously throughout the experiment. The remaining plants were allowed to grow three primocanes each. Captan 50WP was sprayed to the gird led zone at a rate of 0.5 gL-1 the same day of girdling.

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64 Reproductive Measurements Flowers and fruits per cane were reco rded every other day beginning on 11 May 2004. Fruit were harvested at pink or red color stage (Perkins -Veazie and Nonnecke, 1992). Fruits were weighed and kept frozen at -20o C. After fruit harvest, plants were divided into roots, canes, la terals and primocanes, fres h weight obtained and plant segments dried at 80o C until constant weight. Fruits from peak of harvest were analyzed for quality as explained in Chapter 3. The remaining fruits were dried at 80o C and dry weight obtained. Photosynthesis Net photosynthesis (Pn) was determined by measuring the CO2 assimilation rate in floricane and primocane leaves with a porta ble gas exchange analyzer (LiCor LI-6400; Lincoln NE, USA.) operated as an open syst em. The uppermost fruiting laterals in the top, middle, and lower sections of each flor icane were selected and Pn was measured on the fully open distal leaf of each lateral. Data from the three sections in each floricane were pooled to determine the floricane Pn. In primocanes, the uppermost fully open leaf was selected and Pn was determined on the distal leaflet. Plants were watered (2 L/pot) the day before CO2 measurements. Photosynthesis was measured between 9:00 and 11:00 a.m. (2.5 to 4.5 hours after sunrise) every w eek from the peak of fruiting (2 June, 2004; 85 DAP) through 24 June, 2004 (107 DAP) when 80% of fruits had been harvested. Experimental Design A 2x2 factorial was used to study the effect of girdling (girdling vs. no girdling) and primocane removal (3 vs. 0 primocanes per pot). Treatments were arranged in the tunnel in a randomized complete block design wi th cane vigor and diameter used as block determinants. There were six replications per treatment and one plant (pot) was

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65 considered an experimental unit. All girdled canes without primocanes died 20 days after girdling and they were not considered for furt her analysis. Remaining treatments were (1) non-girdled canes with primocanes (Control) (2) non-girdled canes without primocanes and (3) girdled canes with primocanes. Data fr om these three treatments were analyzed as a complete randomized block design by using the GLM procedure in SAS (SAS institute Inc., Cary, NC USA. 2002). Results Girdled canes without primocanes began dyi ng 20 days after gird ling and all plants in this treatment died during fruit harvest. In order to avoid bias in the inferences, this treatment was not included in the statistical analysis. Flower counting began at 63 DAP. At this point, more than 40% of the total flowers were already opened. Bloom ended ~18 day earlier in girdled canes compared with the non-girdled control canes, but prim ocane removal in non-girdled canes had no effect on the end of bloom (Table 5-1). Nongirdled canes had a second flush of flowers around 90 DAP (Fig 5-1A). The pattern of fruiting was similar in all treatments (Fig 5-1B). Treatments had no significant effect on the beginning or the end of fruiting, but frui ting period length was reduced by 9 days in girdled canes compared with non-girdled canes. Primocane removal in the non-girdled canes had no effect on fruiting period le ngth (Table 5-1). There was little effect of treatment on yield components, although yield/cane was reduced in the girdled + primocane treatment (P< 0.11) compared with the two nongirdled treatments (Table 5-2). There was al so little treatment effect on dry weight allocation within the plants, ex cept for a reduction in root dr y weight in the non-girdled +

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66 no primocane treatment compared with the treatments in which 3 primocanes were present, regardless of girdli ng treatment (Table 5-3). In general, photosynthesis was greater in non-girdled compared with girdled canes, regardless of the presence of primocanes. Howe ver, differences were significant only at 85 and 100 DAP (Table 5-4). Fruit soluble solids in the non-girdled + primocane removal treatment were increased slightly compared with the non-gi rdled + primocane treatment (p=0.09), but there were no treatment effects on titratable acidity or the soluble solids to titratable acidity ratio (Table 5-5). Discussion The effect of girdling on end of bloom and shortening of the fruit harvest period may result from a decrease in carbohydrate availa bility in the girdled floricanes late in the flowering period. In red ras pberry, flower bud initiation occu rs basipetally from late summer through winter and some flowers diffe rentiate in the lower cane after bloom onset in the spring (Williams, 1959; Qingwen and Jinjun, 1998). Ca rbohydrates play a role in flower bud initia tion and development in Sinapsis alba L. (Bodson and Outlaw, 1985), Vaccinium ashei Reade (Darnell, 1991) and Diospyros kaki L (Ooshiro and Anma 1998). In red raspberry, the increasing demand for carbohydrates in flor icanes during leaf and flower development is fulfilled first with cane, then with root carbohydrates (Whitney, 1982; Fernandez and Pritts, 1993). In the present experiment, girdling was done around peak of bloom (62 DAP), pr eventing further movement of carbohydrate from roots to floricanes. This may have resulted in a carbohy drate limitation that decreased initiation and devel opment of flowers in the lowe r parts of the floricane and shortened the bloom and fruiti ng periods. Although not statistically significant, there was

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67 a 22% decrease in flower number and a 15% de crease in fruit number (p=0.14) in girdled compared with non girdled canes. Earlier gird ling may have had a much more serious effect on decreasing flower initiation and fruit number, especially in the lower part of the floricane Although the decrease in flower and fru it number in girdled floricanes was not statistically significant compar ed with the non-girdled floricanes, leaf Pn of girdled floricanes was reduced compared to Pn of non-girdled canes. This may be a consequence of reduced sink demand in the girdled canes. Pr evious studies have shown that low fruit loads can decrease photosynthesis in gird led branches of citrus (Iglesias et al., 2002), apple (Zhou and Quebedeaux, 2003) and mango (Urban et al., 2004) compared with either non-girdled or girdled branches with hi gh fruit loads. Floric anes are also a source of carbohydrates to roots during the fruiti ng period (Fernandez and Pritts, 1993). The decreased sink demand due to th e reduction of flowers and fru its in girdled floricanes, added to the isolation of the root system and therefore elimination of the roots as a sink, might result in a decrease in floricane photosynt hesis. Regardless of the differences in Pn among treatments in this experiment, Pn for a ll treatments were similar to previous work on raspberry in traditional cropping systems (Oliveira et al., 2004) Although girdling often increases yield a nd fruit quality in some crops, due presumably to increased carbohydrate accu mulation above the girdle (Allan et al., 1993), girdling slightly decreased yield in the presen t experiment. This may be due to a cascade of effects that girdling exerte d on the floricane. First, an initial reducti on of root carbohydrates moving to the floricane, followed by a reduction in flower and fruit number, which, in turn, decreased net photos ynthesis and ultimately assimilates for fruit

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68 development. Others have also reported that girdling had no effect on fruit yield (Iglesias et al., 2002). Fruit citric acid in this experiment was about three times the maximum proposed for raspberry (Kader, 2001). Plants were wate red as explained in Chapter 4 and crumbly fruits were also frequent. In order to avoid fruit loss, ha rvest was done at pink and red color stages resulting in higher citric acid co ntent in fruits from this experiment. Fruit soluble solids, however, remained above the minimum proposed by Kader (2001). Primocane removal decreased root dry we ight but had no effect on floricane dry weight. Both primocanes and floricanes are sources of assimilates for roots, but there appears to be no reciprocal translocati on of assimilates between primocanes and floricanes (Fernandez and Pritts, 1993). Floricanes appear to act as carbohydrate sources for r oots in red raspberry under some conditions, as observed by Fernandez and Pritts (1993). This is supported by the normal flowering and fruiting that occurred in non-girdled canes without primocanes, where the only source of carbohydrates to r oots would be the floricane. Additionally, girdled canes without primocanes died within 20 days of girdling, which may have been due to elimination of floricanes as a carbohydr ate source for roots resulting in a severe carbohydrate limitation in the roots. Conclusion Girdling resulted in a significant reducti on in the fruiting period and tended to decrease flower and fruit number per can e. Girdling prevente d root carbohydrate translocation to the floricane during the latter part of the blooming season, and apparently decreased flower bud initiation/ differentiation in the lower portion of the cane. Primocane removal had little effect on growth and deve lopment, other than decreasing root dry

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69 weight. Primocanes appear to be the main source of carbon for roots; however, the carbohydrates allocated to roots from primo canes have no effect on floricane growth, since primocane removal did not affect dry we ight accumulation in floricanes. Floricanes appear to be a carbohydrate s ource to roots as well, but in limited amounts, which do not affect their own growth.

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70 0 50 100 150 200 250 300 350 400 60708090100110120130 Days after plantingFlowers per cane Non girdled + 3 Primocanes Non girdled + No Primocanes Girdled + 3 Primocanes A 0 5 10 15 20 25 30 35 40 45 50 60708090100110120130 Days after plantingFruits per cane Non girdled + 3 primocanes Non Girdled + No Primocanes Girdled + 3 Primocanes B Figure 5-1. Effect of girdli ng and primocane removal on bl oom (A) and fruiting (B) in ‘Tulameen’ red raspberry in a winter production system. Arrows indicate the girdling time (62 days after planting) (n=6).

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71 Table 5-1. Effect of girdling and primocane removal on bloom and fruiting in Tulameen red raspberry in a winter production system (n=6). Treatment End of bloom (DAP)z Beginning of fruiting (DAP) End of fruiting (DAP) Fruiting period length (days) Non-girdled + 3 primocanes 109.5ay 71.7 114.7 43.0a Non-girdled + no primocanes 109.5a 74.7 118.0 43.3a Girdled + 3 primocanes 91.0b 74.1 108.5 34.3b P -value 0.002 0.76 0.17 0.08 z DAP= Days after planting yLSMean separation by Tukey at the indicated P -value Table 5-2. Effect of girdling and primocane removal on yield components of Tulameen red raspberry in a winter production system (n=6). Treatment Flowers per cane Fruits per cane Fruit set (%) Yield per cane (g) Fruit size (g) Non girdled + 3 primocanes 180.0 60.0 36.8 160.4 2.65 Non girdled + no primocanes 164.8 64.5 43.1 145.6 2.27 Girdled + 3 primocanes 139.8 50.8 38.3 116.9 2.31 P -value 0.58 0.14 0.77 0.11 0.16 Table 5-3. Effect of girdling and primocane removal on dry weight allocation in Tulameen red raspberry in a winter production system (n=6) Dry weight (g) Treatment Roots Floricane Primocanes Laterals Fruits Totalz Non -girdled + 3 primocanes 32.9ay29.8 35.4 32.5 24.1a 119.4 Non-girdled + no primocanes 26.4b 30.7 ND 29.2 24.6a 111.0 Girdled + 3 primocanes 35.2a 32.1 39.1 27.5 17.8b 112.5 P -value 0.005 0.35 0.15 0.54 0.10 0.57 z Primocanes are not included yLSMean separation by Tukey at the indicated P -value Table 5-4. Effect of girdling and primo cane removal on leaf photosynthesis (mol CO2m-2s-1) of Tulameen red raspberry in a winter production system (n=6) Day after planting Treatment 85 92 100 107 Non-girdled + 3 primocanes 11.03az 8.45 8.78ab 5.62 Non-girdled, no primocanes 11.75a 7.47 9.35a 4.87 Girdled + 3 primocanes 8.77b 6.93 7.05b 3.75 P -value 0.011 0.125 0.054 0.336 zLSMean separation by Tukey at the indicated P -value

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72 Table 5-5. Effect of girdling and primocane removal in ‘Tulameen’ raspberry fruit quality in a winter production system (n=6). Treatment Soluble Solids (%) TA (% of Citric acid) SSC/TTA ratio Non Girded + 3 primocanes 11.15b 2.33 4.87 Non girdled + 0 primocanes 12.08a 2.34 5.24 Girdled + 3 primocanes 11.85ab 2.52 4.77 P-value 0.091 0.348 0.331

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73 CHAPTER 6 ROOT PRUNING EFFECTS ON GROWTH AND YIELD OF RED RASPBERRY (Rubus idaeus L.) There is increasing interest in off-season production of raspberry, necessitating the need for new cropping systems. In south Flor ida, an annual production system has been examined, in which pre-chilled long cane ras pberry cultivars are purchased from northern nurseries and field-planted in late January. Fr uit harvest occurs as early as March (Knight et al., 1996). In this annual system, raspberry plants ar e removed after harvest and replaced with new pre-chilled long canes for th e next season. The disturbance of the root system during digging and shipment from the nursery leads to signi ficant root loss and may alter the root-shoot balance in such a way that results in yield decreases. Many studies have shown that root pruning in temperate crops affects shoot growth and yield. Dormant root pruning reduced ve getative growth and fruit size in apple (Schupp and Ferree, 1987; 1989), grape (Ferree et al., 1999; Lee and Kang, 1997) and sweet cherry (Webster at al., 1997). However, root pruning du ring bloom had no effect in apple (Elfving et al., 1991) or apricot (Arzani et al., 1999). The different effects of root pruning may be due to differences in root carbohydrate mobilization to the shoot. Dormant pruning would remove a large sour ce of reserve carbohydrate that would normally be used to support vegetative and/ or floral budbreak. Ho wever, delaying root pruning until bloom would allow translocation of root carbohydrates prior to the root pruning treatment, thus the carbohydrate s upply to support budbreak would not be limited.

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74 In raspberry, spring vegetative and reproduc tive growth are concomitant (Atkinson, 1973) and both need carbohydrate for production of new biomass. Primocanes also begin growth at this time and are an additional sink for root carbohydrates (Whitney, 1982). Root pruning could further exacerbate car bohydrate competition sinc e root growth also increases after root pruning (Schupp et al., 1992), resulting in additional sink activity. Given this scenario and the low photosynthetic activity in floricane leaves before bloom (Fernandez and Pritts, 1994), th ere is a high probability that roots of raspberry plants, especially in an annual production syst em, may be carbohydrate depleted by the beginning of bloom. Root carbohydrate depletion would affect not only spri ng shoot growth and early flower/fruit set, but could al so affect flower bud initiati on/differentiation in raspberry. Flower bud initiation/differentiation in the lowe r portion of raspberry floricanes continues during early bloom (Williams, 1959; Qingwen and Jinjun, 1998) and adequate carbohydrate supply is critical for this pro cess (Bodson and Outlaw, 1985; Darnell, 1991; Ooshiro and Anma, 1998). Therefore, the elimin ation of part of the root system during dormancy could decrease the ca rbohydrate reserves required for early floricane lateral growth, including flower bud initiation. Cons equently, fruit number and yield would decrease. Additionally, root pr uning may also affect cane yi eld by decreasing fruit size. Fernandez and Pritts (1996) found that the maximum demand for assimilates in red raspberry is at the onset of fruiting while prim ocanes, roots, and fruits are all growing. In an annual cropping system, the elimination of pa rt of the root system and the consequent

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75 intensive root regeneration (Schupp et al., 1992) during the high sink activity of the raspberry plant could decrease carbohydrate availability for the developing fruit. The hypothesis in the present experiment was that root pruning decreases cane carbohydrates in red raspberry during budbreak and early bloom, resulting in a decrease in yield. The objectives were to assess th e effect of root pr uning on yield and plant carbohydrate allocation. Materials and Methods The experiment was conducted at the University of Florida in Gainesville, Florida. (29.69N and 82.35W). The tunnel, trellisi ng system, heating and ventilation were described in Chapter 3. The substrate and potti ng system were as described in Chapter 5. Plant Material Bare-root long canes of the summer beari ng red raspberry cultivar Cascade Delight were purchased from a commercial nursery in the Northwest U.S. Canes arrived in midJanuary 2004, and roots were wrapped in wet cy press sawdust as in previous years. Canes were placed in a dark walk-in cooler at 7o C for 1320 hours On 11 Mar. 2004, canes were potted in 36. 7 L black polyethylene containers as described in Chapter 5 and placed outdoors. Plants were hand-watered with 2L water per pot three times a week and fertilized with a water soluble fertilizer (20N-8.8P-16.6K; J.R. Peters, Inc. Allentown, Penn.) at a rate of 0.6 g of nitrogen per pl ant. Phytophthora root rot, leaf fungal diseases a nd two-spotted spider mite c ontrol were achieved by using Captan 50 WP, Subdue maxx, and a commercial mi xture of mite predators, respectively, as indicated in Chapter 5.

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76 Canes were allowed to fruit during the season, and fruits were harvested when ripe. All primocanes in the contai ner were allowed to grow throughout the season and only floricanes were pruned at the me dia level after fruit harvest. In Dec. 2004, 24 plants were selected for the experiment. Two primocanes per plant were selected based on uniform height and vi gor and the rest were pruned at the media level. Half of the plants were root pr uned in early December. Root pruning was performed with a sharp machete and roots were pruned to a 12x12x12 cm3 volume, removing approximately 45% of the root dr y weight. After root pruning, four rootpruned and four non root-pruned plants were se parated into roots, canes, and leaves and fresh weights measured. Plan t tissues were dried at 80o C until constant weight and dry weights were recorded. The remaining plants were placed in a dark walk-in cooler on 13 Dec. The cooler temperature was 10o C for 240 hours, then decreased to 7o C for an additional 980 hours. On 31 Jan. 2005, chilled canes were moved to the tunnel and auxiliary heating and ventilation was done as described in Chapter 3. Plant watering, fertilizing, and pest control in the tunnel was performed as explained above. At budbreak in early March, four root-pr uned and four non root-pruned plants were harvested and processed as de scribed above. The remaining pl ants were allowed to grow and fruit. Three new primocanes were allowed to grow per plant. Bumble bees (Bombus impatients) were released at the beginning of bloo m in early April to improve pollination. Flowers and fruits were count ed and fruits were hand-harv ested at pink and red color stages, weighed and either dried at 80o C until constant weight or kept frozen at -21o C for fruit quality analysis as explained in Chap ter 3. Each plant was harvested individually at the end of fruit harvest. Plants were divided and processed as described above.

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77 Photosynthesis Net photosynthesis (Pn) was determined by measuring the CO2 assimilation rate in floricane and primocane leaves with a porta ble gas exchange analyzer (LiCor LI-6200; Lincoln NE, USA.) operated as an open sy stem. Photosynthesis was measured between 10:00 and 12:00 a.m. (3 to 5 hours after sunris e) at beginning of bloom (5 Apr. 2005; 64 days after planting (DAP)) and at the peak of fruit harvest (13 May; 102 DAP). The uppermost fruiting laterals in the top s ection of each floricane were selected. Photosynthesis was measured on the distal leaf let of the most distal fully open leaf of each lateral. In primocanes, the uppermost fully open leaf was selected and Pn was determined on the distal leaflet. Plants were watered (2 L/pot) the day before CO2 measurements were taken. Carbohydrate Analysis Soluble sugars and starch in roots, flor icanes (laterals, cane, and fruits), and primocanes (when present) were measured Dried tissue was ground and passed through a 20 mesh screen (1.27 mm mesh). Soluble suga rs were determined by extracting 50 mg of ground tissue in 2 mL 80% etha nol (1:100 w/v). Tissue was shaken for 20 minutes at 150 rpm on an orbital shaker (Fishe r Scientific Model 361; U.S.A. ). Extracts were centrifuged at 2,270 x g for 10 minutes. After decanting th e supernatant, the re maining pellet was reextracted twice in 1 mL 80% ethanol (1:100 w/v). Supernatants were combined, final volume measured and aliquots used for total sugar analysis. Pigment was removed by mixing 35 mg activated charcoal and centrifugi ng at 14,900 x g for 4 minutes. Percentage recovery was estimated by using 14C-sucrose as an external standard. Soluble sugars were determined by the phenol-sulfuric acid colorimetric pro cedure (Chaplin and Kennedy, 1994) using glucose as a standard and correcting for percent recovery.

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78 Tissue starch content was determined by su spending the insoluble pellet in 2.0 mL 0.2N KOH and boiling for 30 min. The pellet was cooled and adjusted to a pH of 4.5 with 1.0 mL 1M acetic acid. Rhizopus amyloglucosidase (50 units) and -amylase (10 units) (Sigma Chemical Co., St. Louis Mo., U.S.A.) in 0.2M calcium acetate buffer (pH 4.5) were added to each sample. After enzyme addition, samples were incubated at 37o C for 24 hours while shaking at 78 rpm in a constant temperature bath (Mag ni Whirl. Blue M. Blue Island, IL. U.S.). After incubation, sa mples were centrifuged at 2, 270 x g for 10 minutes and the supernatant decanted, measured, and aliquots used for sugar analysis. Supernatant pigment was removed by mixing 35 mg activated charcoal and centrifuging at 14,900 x g for 4 minutes. Percentage recove ry was estimated by using 14C-sucrose as an external standard. Glucose obtained fr om starch hydrolysis was quantified by the phenol-sulfuric acid method (Chaplin and Ke nnedy, 1994) using glucose as standard and correcting for percent recovery. Experimental Design The two root treatments and three plant harvest dates were analyzed as a 2x3 factorial for carbohydrate content and dry weight allocati on. Treatments were distributed in the tunnel as a randomized complete block design. There were four replications per treatment with single-plant experimental units. Yield components, photosynthesis, and fruit quality were analyzed as one-way ra ndomized complete block design. Data were analyzed with the GLM procedure of SAS (SAS Inst. Inc., Cary, N.C.). Results There were no significant interactions between root pruning and time of plant harvest on any variable; thus, only main effects are presente d. Root pruning significantly decreased dry weight partitioning to fruit compared with no root pruning (Table 6-1).

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79 Root dry weight also decreased as a result of root pruning; however, there were no effects of root pruning on floricane, latera l shoot, or primocane dry weight. Dry weight of all organs except flori canes increased as the season progressed (Table 6-1), resulting in a signi ficant increase in total plant dry weight at the end of the growing season. Root pruning decreased the number of flowers per cane compared with the non root-pruned canes (Table 6-2). This decrease resulted in significantly less fruits per cane and consequently lower yields per cane in the root-pruned canes Fruit size was not affected by root pr uning (Table 6-2). Fruit quality was generally unaffected by r oot pruning except for a slight decrease in soluble solids in root-pruned compared with non root-pruned plants (p=0.06), However, the decrease in fruit soluble solids resulted in a significant decrease in the soluble solids to acidity ratio (Table 6-3). Re gardless of the treatments, fruit soluble solid remained above the minimum proposed for ra spberry (Kader, 2001). Fruit citric acid, however, was three times the maximum propos ed for this crop, resulting from the non fully ripe stages of harvest as explained in Chapters 4 and 5. Net photosynthesis in this experiment was similar to previous work on raspberry in traditional cropping systems (Oliveira et al, 2004). However, in this experiment, Pn was significantly lower in floricane leaves of root-pruned canes compared with floricane leaves of non root-pruned canes at the beginning of bl oom (64 DAP). There were no differences in leaf Pn at the peak of fru it harvest (102 DAP)(Table 6-4). Primocane leaf Pn was measured only at peak of harvest and was not affected by root pruning.

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80 Root pruning did not affect soluble sugar or starch concentration in any organ or in the whole plant (Tables 6-5 a nd 6-6). However, total carbohy drate concentration (soluble sugars + starch) was significantly lower in ro ots of root-pruned plants compared with non root-pruned plants (Table 65). On the other hand, total carbohydrate concentration in primocanes of root-pruned plants was signifi cantly higher than primocanes of non rootpruned plants (Table 6-5). Soluble sugar concentration decreased in roots and laterals between the time of root pruning (mid-Dec.) and budbreak (mid-March ) (Table 6-5). Root soluble sugar concentrations then increase d between budbreak and fruit ha rvest, at which time they were similar to concentrations at the time of root pruning. Soluble sugar concentrations in laterals continued to decrease through the end of fruiting. On a whol e plant basis, soluble sugar concentration was significantly lower at budbreak compared w ith the other harvest times (Table 6-6). Root starch concentration was lowest at budbreak and increased significantly by the end of fruit harvest (Table 6-5). Similarly, starch concentration in both laterals and primocanes was lower at budbreak than at th e end of fruit harvest (Table 6-5). On a whole plant basis, starch concentration was significantly lower at budbreak compared to the other harvest times (Table 6-6). Total carbohydrate concentra tion (soluble sugars + starch ) in all organs decreased at budbreak, but this was signi ficant only in roots (Table 65). However, on a whole plant basis, total carbohydrate con centration was significantly lo wer at budbreak than at the other harvests (Table 6-6).

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81 Discussion The decrease in root dry weight af ter root pruning was expected, since approximately 45% of the total root dry wei ght was removed at pruning. However, the lack of interaction between root pruning a nd harvest time on root dry weight indicates that root growth occurred at the same rate in both root and non root-pruned plants. The lack of significant effect of root pruning on dry weight alloca tion to plant structures other than roots and fruits suggests that raspberry shoot growth may be relatively independent from the root carbohydrate supply in this pr oduction system. In the present experiment; however, root pruning decrease d floricane lateral dry weig ht by ~50% compared with lateral dry weight of non root -pruned plants. Even though th e decrease in lateral dry weight of root-pruned plants was not signifi cant, it might indicate the relative importance of root carbohydrates for ini tial lateral growth. In ras pberry, the main source of assimilates for growth of fruits and latera l apices is the nearest photosynthetic leaf (Fernandez and Pritts, 1993; Prive et al.,1994), but root carbohydrat es become important for shoot growth when current carbohydrates availability is re duced (Fernandez and Pritts, 1994). The negative impact of root pruning on yield per cane was the result of the reduction in flowers per cane and consequently the reduction in fruits per cane. Flower bud formation occurs in the lower part of re d raspberry canes as late as spring, right before budbreak (Williams (1959). Additiona lly, pistils and anthers are still differentiating in late April under cool temperatures (10o C average) (Qingwen and Jinjun, 1998). Initiation and di fferentiation of flowers in raspberry require carbohydrate, as found in other crops (Bodson and Outlaw, 1985; Darnell, 1991; Ooshiro and Anma 1998) and, because of the lack of photosynthe tic leaves during flower differentiation,

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82 carbohydrate requirements must be supplied by re serves from the previous year. Whitney (1982) reported that red ras pberry root dry weight decrea sed at budbreak and suggested that assimilates from the root were mobilized to the floricanes and primocanes during this time. In our experiment, there was also a decrease in root dry weight at budbreak, although it was not significant comp ared with root dry weight at the time of root pruning. However, root and whole plant carbohydrat e concentration decreased significantly between the time of root pruning a nd budbreak. The lower root carbohydrate concentration in root-pruned plants compar ed to non root-pruned plants during budbreak may have limited flower bud formation duri ng budbreak, resulting in decreased yield At the beginning of bloom (64 DAP), Pn was significantly higher in non rootpruned plants than in rootpruned plants. This difference might result from the lower fruit number in root-pruned plants, as lo wer fruit loads decrease sink activity and consequently photosynthesis in some crops (Iglesias et al., 2002; Zhou and Quebedeaux, 2003; Urban et al., 2004). The difference in photosynthesi s, however, disappeared at the peak of harvest (102 DAP), possi bly as a result of a decrease in the sink/source ratio as bloom ended and more leaves attained photos ynthetic competence. The higher Pn in non root-pruned plants during bloom might explain the higher fruit soluble solids concentration compared with fruits from root-pruned plants. The higher soluble sugar and starch con centration in roots of non root-pruned compared with root-pruned plants may be due to the higher photosynthetic rate in non root-pruned plants. Floricane leaves serve as a source of assimilates for roots (Fernandez and Pritts, 1993) and the movement of carbohydr ate from floricanes to roots is common once the floricane leaves are activ ely photosynthetic (Whitney, 1982).

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83 During the growing season, roots need carbohydrates for growth as well as for storage, and primocanes are the primary s ource of carbohydrates for the root (Whitney, 1982; Fernandez and Pritts, 1993). In the pr esent experiment, primocane growth was similar between the two root pruning treatments Root growth rates were also similar, as inferred from the absence of an interacti on between root pruning and time of plant harvest. However, the reduction of about 45% of the root syst em in the root-pruned plants might decrease total root sink activity, resulting in incr eased carbohydrate concentration in primocanes from root-pruned compared with non root-pruned plants. The higher carbohydrate concentration in primocanes from root-pruned plants; however, was apparently not sufficient to significan tly decrease primocane photosynthesis. Conclusion Cane yield in red raspberry is decreased by dormant ro ot pruning via the reduction of flowers per cane; however, fruit size is no t affected. The reduction of flowers per cane in root-pruned raspberry plan ts appeared to be mediated by the reduction in root carbohydrate availability at budbreak, when some flowers are still differentiating. This decrease in carbohydrate availability was due to the loss of almost half the original carbohydrate reserves after root pruning, ev en though the carbohydrat e concentration in roots was not affected by pruning. Car bohydrate concentration in other floricane structures was not affected by root pruning, indicating that these organs are less dependent than flowers on root carbohydrat es for growth. Fruit set and fruit size remained unaltered by root pruning, suggesting th ey may rely more on current than stored photosynthates.

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84 Table 6-1. Effect of dormant root pruning on dry weight allocation in ‘Cascade Delight’ red raspberry in a winter production system in north Florida (n=4). Dry weight (g) Factor Root Laterals Floricane PrimocaneFruits Total Treatment Root-pruned 75.2z 21.9 27.0 155.9 36.5 194.9 Non root-pruned 135.7 45.4 37.9 130.9 67.8 248.0 P-value 0.001 0.12 0.12 0.67 0.003 0.59 Harvest timey Pruning 76.2bx NDw 36.9 ND 137.6b Budbreak 61.6b 6.1b 29.1 3.6b 58.2b End of fruiting 178.4a 61.2a 31.3 290.4a 468.6a P-value 0.0003 0.01 0.61 0.01 0.007 zMeans of the same factor with in the same column are differe nt by t-test at the indicated P-value. y Plants were harvested at root pruning ( 11-16 Dec. 2004), budbreak (11 Mar. 2005) and after fruit harvest (9 June to 16 July 2005) xLSMean separation by Tukey at the indicated P-value w No data available Table 6-2. Effect of dormant root pruning on yield components of ‘Cascade Delight’ red raspberry in a winter production system in North Florida (n=4) Treatment Flowers/cane Fruit/cane Fruit set (%) Yield/cane (g) Fruit size (g) Root-pruned 146.0 85.3 60.3 380.4 4.32 Non rootpruned 284.8 148.8 51.4 658.9 4.46 P-valuez 0.04 0.0006 0.7 0.01 0.64 zMeans within the same column are differe nt by t-test at the indicated P-value. Table 6-3. Effect of dormant root pruni ng on fruit quality of ‘Cascade Delight’ red raspberry in a winter production system (n=4). Treatment pH Soluble solids (%) TA (% Citric acid) SSC/TTA Root-pruned 2.99 9.3 2.6 3.5 Non root-pruned 3.09 10.3 2.5 4.2 P-valuez 0.283 0.06 0.18 0.002 zMeans within the same column are di fferent by t-test at the indicated P-value.

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85 Table 6-4. Effect of dormant root pruning on leaf photosynthesis Pn of ‘Cascade Delight’ red raspberry in a winter production system in North Florida (n=4). Pn (molm-2s-1) Treatment 64 DAPz 102 DAP Floricanes Root-pruned 3.80y 5.65 Non root-pruned 8.34 4.80 P-value 0.03 0.73 Primocanes Root-pruned NDx 6.86 Non root-pruned ND 7.04 P-value 0.94 zDAP=Days after planting yMeans within the same column are di fferent by t-test at the indicated P-value. xNo data available

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86Table 6-5. Effect of root pruning and ha rvest time on carbohydrate concen tration of ‘Cascade Delight’ red raspberry in a winter production system in North Florida (n=6) zMeans of the same factor with in the same column are differe nt by t-test at the indicated P-value. y Plants were harvested at root pruning ( 11-16 Dec. 2004), budbreak (11 Mar. 2005) and af ter fruit harvest (9 June to 16 July 200 5) xLSMean separation by Tukey at the indicated P-value Glucose concentration (g/mg dry weight) Root Floricane Laterals Fruit Primocanes Treatment Sol.Sug. Starch Total Sol.Sug. Starch Total Sol.Sug. Starch Total Sol.Sug. Starch Total Sol.Sug. Starch Total Root-pruned 14.4z 45.9 60.3 22.3 34.6 57.0 65.0 29.1 94.1 113.5 11.5 125.0 40.0 31.8 71.9 Non root-pruned 17.6 53.4 71.0 19.3 34.4 53.7 61.4 33.4 94.7 107.9 2.4 110.3 26.7 26.2 53.0 P -value 0.47 0.10 0.06 0.41 0.98 0.76 0.51 0.37 0.93 0.21 0.23 0.13 0.09 0.36 0.04 Harvest timey Pruning 23.8ax 49.6ab 73.4 21.0 44.7 65.7 83.9a 26.6ab 110.5a Budbreak 7.6b 35.8b 43.4 26.2 21.0 47.2 63.7b 24.9b 88.6ab 36.1 21.1 54.1 End of harvest 16.6ab 63.6a 80.2 15.2 37. 8 53.0 41.9c 42.2a 84.2b 110.7 7.0 117.7 30.6 37.0 67.6 P -value 0.05 0.004 0.001 0.14 0.12 0.39 0.001 0.04 0.04 0.46 0.06 0.22

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87 Table 6-6. Effect of root pruning and harv est time on total carbohydrat e concentration of Cascade Delight red raspbe rry plants in a winter production system in North Florida (n=4) Glucose concentration (g/mg dry weight) Treatment Sol.Sugars Starch Total Root-pruned 28.9z 35.6 64.4 Non root-pruned 26.2 41.1 67.3 P -value 0.37 0.10 0.49 Harvest timey Pruning 29.8ax 44.1a 73.9a Budbreak 18.3b 27.5b 45.7b End of harvest 34.5a 43.4a 77.9a P -value 0.008 0.004 0.0005 zMeans of the same factor with in the same column are differe nt by t-test at the indicated P -value. y Plants were harvested at root pruning ( 11-16 Dec. 2004), budbreak (11 Mar. 2005) and after fruit harvest (9 June to 16 July 2005) xLSMean separation by Tukey at the indicated P -value

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88 CHAPTER 7 SUMMARY AND CONCLUSIONS The increasing interest in raspberry produc tion in nontraditional growing regions in the U.S. has resulted in the implementati on and testing of new cropping systems. An annual winter production system has been proposed for subtropical Florida (Knight et al, 1996). This system relies on na turally chilled bare-root l ong cane raspberry cultivars obtained from northwestern nurseries and fiel d-planted in south Fl orida during winter. With this system, fruit harvest begins in early March, i.e. three months earlier than the earliest ripening summer cultivar s, which usually begin to produ ce ripe fruits in mid-June in the western U.S. (WRRC., 2005). Implementation of night’s system in nor thern Florida, where severe freezes may occur during winter, would require some ad aptations. Polyethylene tunnels (Oliveira et al., 1996) can provide protection during freezes and artificial heat will ensure sufficient heat accumulation for uniform cane b udbreak inside the tunnel (Carew et al., 1999). Thus, tunnel production offers the possibility of advancing planting time, resulting in fruit harvest earlier than March. In this research, the feasibility of a winter raspberry production system under polyethylene tunnels was determined. Two re d raspberry cultivars, the summer bearing ‘Tulameen’ and the fall bearing ‘Heritage’, were compared each at two in-row spacings (25 and 50 cm) with rows spaced at 1. 8 m. Canes were planted on 28 Dec. 2001 following a chilling period of 1200 h at 4o C. Fruit harvest bega n in early March, 2002. Yield per cane decreased at 25 cm compared with the 50 cm in-row spacing, but the

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89 higher number of canes at the shorter in-row sp acing resulted in an estimated higher yield per hectare. There were cultivar differences in cane yield. Yield per cane, and fruit size were greater in ‘Tulameen’ compared with ‘Heritage’ and fruit quality was better. Furthermore, the fruit harvest period for ‘T ulameen’ was shorter than for ‘Heritage’, making ‘Tulameen’ more suitable for this system. Although decreasing in-row distance from 50 to 25 cm slightly decreased fruit so luble solids, fruit quality was generally not affected, as both soluble solid s and acidity were within optimum standards for raspberry fruits (Kader, 2001). This experiment indicated that the annual tunnel production system appears technically feasible. However, yield, fr uit size, and fruit number per cane in both cultivars were reduced compared with ot her reports on yield obtained in these two cultivars (Dale et al., 2001; Daubeny and Anderson, 1991; Myers, 1993). The annual cropping system tested for raspberry in this research depended on root pruning during plant removal from the nursery. Root car bohydrates support cane growth during early budbreak (Whitney, 1982; Fernadez and Pritts, 1993) when the initial leaf canopy is not photosynthetically active. Thus, further expe riments were conducted to determine the importance of root for floricane yield a nd growth. The approach included floricane girdling, primocane removal and root pruning. In general, complete girdling (rem oval of bark around the whole cane circumference) decreased flower number when done either before bloom or peak of bloom; however, girdling had no effect on flow er number when done at peak of harvest and/or when done incomplete (remova l of the bark around 75% of the cane

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90 circumference) Similarly, root pruning decrea sed flower number per ca ne and resulted in cane yield reduction. Carbohydrate analysis indicated that root and total plan t carbohydrate concentration (soluble sugars and starch) decreased at budbrea k, then increased at the end of harvest. Carbohydrate concentrations in floricanes and fruiting laterals did not decrease at budbreak, suggesting that carbohydrates moved fr om roots to floricanes and laterals during budbreak. Flower bud initiation/differentia tion in raspberry starts during the fall in the cane tip and continues during early bloom in the lower portion of cane (Williams, 1959; Qingwen and Jinjun, 1998). Adequate ca rbohydrate supply is critical for this process (Bodson and Outlaw, 1985; Darnell, 1991; Ooshiro and Anma, 1998). Reduction of carbohydrate availability to nodes in the lower cane -either by root pruning or by girdling at early or peak of bloomapparently decreased flower number in the lower part of the cane, resulting in decreased yield per cane. Floricane vegetative growth and primocane growth were not affected by girdling or root pruning as showed by fi nal dry weight distribution. Apparently, root carbohydrates are no longer important for shoot growth once current carbohydr ates are available (Whitney, 1982; Fernandez and Pritts, 1993). Raspberry annual winter production under polyethylene tunnels is technically feasible but further analysis is required to evaluate its ec onomic feasibility Root pruning during plant removal from the nursery appears to decrease yields in this annual system. This reduction in yield likely results from the reduction of root carbohydrate available to support flower formation in the lower cane a nd a consequent reduction in flower number.

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91 APPENDIX A YIELD PER AREA IN WINTER 2003 Table A-1. Maximum estimated yield per ar ea obtained in an annual winter cropping system in North Florida and its compar ison with previously reported yield. Factor Maximum estimated yield obtained (kg/ha)z Previously reported yield (kg/ha)y Source Heritage 25 cm 3,618.7 5,488.8 Myers 1993 50 cm 3,462.7 6,622.2 Myers 1993 Tulameen 25 cm 7,438.5 11,111.0 Daubeny and Anderson 1991 50 cm 5,600.1 22,222.0 Daubeny and Anderson 1991 z Between row space of 1.8 m. y Previously reported yield is extrapolated to the same density as in present experiment

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92 APPENDIX B DAILY TEMPERATURES 0 5 10 15 20 25 30 35 2/173/93/294/185/85/28 Month/dayTemperature (oC) Day Night Daily Avg Figure B-1. Day, night and da ily average temperatures in tunnel during 2002 raspberry crop season in North Florida. Fruit ha rvest from 28 Feb to 16 May. Arrow shows plastic removal from tunnel.

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93 0 5 10 15 20 25 30 35 40 11/3012/301/292/283/304/295/296/28 Month/DayTemperature (oC) Day Night Daily Avg Figure B-2. Day, night and daily average temp eratures in tunnel during 2003 raspberry crop season in North Florida. Fruit harvest from 11 Feb to 14 May. Arrow shows plastic removal from tunnel.

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94 0 5 10 15 20 25 30 35 40 12/301/292/283/294/285/286/277/2 7 Month/DayTemperature (oC) Day Night Daily Avg Figure B-3. Day, night and daily average temp eratures in tunnel during 2004 raspberry crop season in North Florida. Fruit ha rvest from 14 May to 12 July. Arrow shows plastic removal from tunnel.

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104 BIOGRAPHICAL SKETCH Horacio E. Alvarado Raya was born in Guanajuato, Mexico. He obtained his bachelorÂ’s degree at the Plant Science Department of the Universidad Autonoma Chapingo in Mexico, and his Master of Scien ce degree in fruit crops at the Fruit Crops Department of the Colegio de Postgraduados Mexico. He has been a teacher in the Universidad Autonoma Chapingo from 1990 to 2001, where he taught plant biology, plant systematics, regional agriculture and fruit crops. In 2001 he was awarded with a scholarship from the National Council fo r Science and Technology (CONACyT) in Mexico to pursue his Ph.D. at the Horticultu ral Science Department of the University of Florida. After obtaining his Ph.D., he w ill continue teaching at the Universidad Autonoma Chapingo in Mexico.