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 Title Page
 Introduction
 Materials and methods
 Results and discussion
 Note
 Acknowledgement
 Literature cited
 Tables
 The gulf coast and research education...






Group Title: Research report - Gulf Coast Research and Education Center - BRA1995-28
Title: Watermelon hollowheart
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Permanent Link: http://ufdc.ufl.edu/UF00067761/00001
 Material Information
Title: Watermelon hollowheart spring 1995
Series Title: GCREC research report
Physical Description: 7 p. : ; 28 cm.
Language: English
Creator: Maynard, Donald N., 1932-
Gulf Coast Research and Education Center (Bradenton, Fla.)
Publisher: Gulf Coast Research and Education Center, IFAS, University of Florida
Place of Publication: Bradenton FL
Publication Date: 1995
 Subjects
Subject: Watermelons -- Varieties -- Florida   ( lcsh )
Watermelons -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 4).
Statement of Responsibility: D.N.Maynard
General Note: Caption title.
General Note: "October."
Funding: Bradenton GCREC research report
 Record Information
Bibliographic ID: UF00067761
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 73261706

Table of Contents
    Copyright
        Copyright
    Title Page
        Title Page
    Introduction
        Page 1
    Materials and methods
        Page 2
    Results and discussion
        Page 3
    Note
        Page 4
    Acknowledgement
        Page 4
    Literature cited
        Page 4
    Tables
        Page 5
        Page 6
        Page 7
    The gulf coast and research education center
        Page 8
Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida





G-cs s

UNIVERSITY OF
t FLORIDA
Institute of Food and Agricultural Sciences


Gulf Coast Research and Education Center
5007 60th St. E., Bradenton, FL 34203
Bradenton GCREC Research Report
BRA-1995-28 (October)


WATERMELON HOLLOWHEART
SPRING 1995


D. N. MAYNARD


Marston Science
Library
JAN 1 9 1996

University of Florida








GCREC Research Report BRA1995-28


WATERMELON HOLLOWHEART
SPRING 1995

D. N. Maynard1
Gulf Coast Research and Education Center
University of Florida, IFAS
5007 60th Street East
Bradenton, FL 34203

Hollowheart of watermelon is a physiological disorder manifested by the
separation of flesh within the fruit. It is very difficult to externally
distinguish hollowheart fruit from fruit with an intact heart although the former
tend to be somewhat asymmetrical. Non-invasive detection of hollowheart has been
attempted by magnetic resonance imaging (MRI), mammography, fluoroscopy,
ultrasound, and xerography (McCuistion et al., 1995). Following preliminary
evaluation, fluoroscopy was found to be most effective for selection of
hollowheart. Operators were able to identify 20 of 23 melons with hollowheart
using one view. Detection improved to 22 of 23 fruit with hollowheart when fruit
were viewed from two directions. The authors suggest that commercial detection
with fluoroscopy could be incorporated into packinghouse operations. The
Japanese are already using nuclear magnetic resonance (NMR) in Tottori Prefecture
for simultaneous determination of soluble solids and hollowheart (personal
observation).
Most watermelon experts agree that there is a higher incidence of hollowheart in
crown-set fruit than in lateral-set fruit, that seedless varieties have more
hollowheart than seeded varieties, and that there are differences among varieties
in hollowheart susceptibility. Beyond that, there is much speculation as to the
role of water and fertilizer management, temperature, pollination, and other
factors.

Because of the difficulty in understanding the cause of hollowheart, little
research has been reported. Results obtained in Japan (Kano, 1993) confirm that
hollowheart occurs more frequently in crown-set (7th to 8th node) than in
lateral-set (20th node) fruit. The crown-set fruit had fewer but larger cells
than the lateral-set fruit; they also had larger intercellular spaces than the
lateral-set fruit. Accordingly, cell separation occurs because the fewer, less
compacted cells in the crown-set fruit cannot keep pace with the expansion rate
of the rind. When growth rate was depressed by defoliation, the inner cell
growth rate did keep pace with the expansion of the rind and hollowheart did not
occur. These results agree with the notion held by some that watermelon plants
that are 'forced' are more likely to produce fruit with hollowheart.

In these preliminary experiments, a variety observed to be prone to hollowheart -
'Jack of Hearts' and a variety observed to be tolerant of hollowheart -
'Sangria' were selected for study. One experiment provided variable N and K
rates and the other experiment was designed to pinpoint the onset of hollowheart.


IProfessor and Vegetable Extension Specialist.


October










MATERIALS AND METHODS
Fertilizer Experiment:

Seeds of 'Jack of Hearts' and 'Sangria' watermelon were planted in a
peat:vermiculite growing mix in No. 128 Todd planter flats (1.5 x 1.5 x 2.5 in.
cells) on 23 February. The watermelon transplants were grown by a commercial
plant grower.

Soil samples from the experimental area obtained before fertilization were
analyzed by the IFAS Extension Soil Testing Laboratory (Hanlon et al., 1994): pH
= 7.2 (target pH = 6.0) and Mehlich I extractable P = 30 (medium), K = 14 (very
low), Mg = 124 (high), Ca = 744 (adequate), Zn = 2.4 (adequate), Cu = 1.4
(adequate), and Mn = 1.9 (low) ppm.

The EauGallie fine sand was prepared in mid February by incorporation of 0-1.2-0
lb. N-P O -K2O per 100 linear bed feet (Ibf). Beds were formed and fumigated
with mefhylbromide:chloropicrin, 67:33 at 2.3 lb/100 Ibf. Banded fertilizer was
applied in shallow grooves on the bed shoulders at 2.7-0-3.8 lb N-P20s-K 0/100
Ibf after the beds were pressed and before the black polyethylene mulch was
applied. The base fertilizer applied was equivalent to 130-60-182 lb N-P20 -
K2O/A. Later, the polyethylene mulch was removed and additional N as NH NO and
K as K2SO4 were applied to some plots to establish three treatments in addition
to the base; 320-60-180, 130-60-360 and 320-60-360 lb N-P20s-KO /acre. The
polyethylene mulch was replaced after the fertilizer was applied. The final beds
were 32 in. wide and 8 in. high, and were spaced on 9 ft centers with four beds
between seepage irrigation/ drainage ditches which were on 41 ft centers.

The replicated plots were 8-ft long and had six plants each and were repeated
four times in a randomized, complete block design. 'Sangria' served as the
diploid pollenizer for the triploid 'Jack of Hearts'. Leaf samples were obtained
on 8 May (fruit set), 24 May (fruit development), and 6 June (harvest). The
petiole and lamina of the most recently matured leaf from 10 branches in each
plot was selected. The leaves were dried, ground, digested, and analyzed for N
by rapid-flow colorimetry and for K by plasma emission spectroscopy (Hanlon et
al., 1994). Weed control in row middles was by cultivation and applications of
paraquat. Pesticides were applied as needed for control of silverleaf whitefly
endosulfann and esfenvalerate), aphids endosulfann), and gummy stem blight
(chlorothalonil and metalaxyl-chlorothalonil).

Watermelons were harvested on 5 June and 14 June. Marketable fruit (U.S. No. 1
or better) according to U.S. Standards for Grades (1978) were separated from
culls and counted and weighed individually. Soluble solids were determined with
a hand-held refractometer on two fruit from each plot at each harvest and the
incidence and severity of hollowheart were noted on every fruit. Where possible,
the resulting data were subjected to analysis of variance and mean separation was
by Duncan's multiple range test.

Onset of Hollowheart: 'Jack of Hearts' and 'Sangria' watermelons were grown at
the base fertilizer level 130-60-180 lb N-P 0 -K O/acre. Otherwise, cultural
conditions were as outlined above for the Fertilizer Experiment. Pistillate
(female) flowers were tagged on the day that they were open. Fruit resulting
from the pollinated and fertilized flowers were harvested 5, 10, 15, 20, 25, 30,










and 35 days after tagging. The diameter of each fruit was measured before
cutting for determination of the presence of hollowheart.

RESULTS AND DISCUSSION

Temperature (Table 1) during the experimental period from 21 March to 14 June was
higher than normal and rainfall during the fruit development period was less than
normal which provided excellent watermelon growing conditions.

Fertilizer Experiment: Yields of 'Sangria' (Table 2) exceeded those of 'Jack of
Hearts' at the base fertilizer level and when N rate alone was elevated. Yields
of the two varieties were equal when K rate and N and K rate were elevated.
Average fruit weight was typical of the varieties about 13 lb for 'Jack of
Hearts' and 20 lb for 'Sangria'. Fruit weight of 'Sangria' was significantly
higher when K rate was elevated in comparison to the other treatments. Soluble
solids concentration was not affected by variety or fertilizer treatment.
Soluble solids exceeded the 10% specified for optional use in the U.S. Watermelon
grade standards to describe very good internal quality (U.S. Standards for Grades
of Watermelons, 1978). The incidence of hollowheart in 'Jack of Hearts' fruit
was highest at the base fertilizer rate and declined with additions of N and K.
The incidence of hollowheart in 'Sangria' fruit was not affected by fertilizer
rate. Hollowheart was more severe in 'Jack of Hearts' fruit at the base
fertilizer level and with N alone addition than at other rates, and more severe
than in 'Sangria' at those rates.

The concentrations of N and K in 'Jack of Hearts' and 'Sangria' watermelon leaves
at three sampling dates are shown in Table 3. There were no differences in N
concentration among varieties or treatments within sampling dates. However,
there was a tendency for N concentrations to increase over time. This trend also
occurred for K concentration. The N concentrations are all in the high range;
K concentrations at the 8 May sampling date were deficient and were adequate to
high at the other sampling dates (Hochmuth et al., 1995).

Onset of Hollowheart: Fruit diameter generally increased with time, but the rate
of increase was most rapid 10 to 15 days after pollination (Table 4). The round-
fruited variety, 'Jack of Hearts' had a larger fruit diameter than 'Sangria' with
elongated fruit. The appearance of hollowheart was erratic since it was noted
in 'Jack of Hearts' only at 10 days and 30 days and in 'Sangria' only at 35 days
after pollination. Because of the failure of many tagged fruit to set, the
numbers of fruit at each sampling were small and variable. Accordingly, it would
be necessary to tag a very large number of fruit for each interval if this
experiment is to be repeated. In experiments with similar objectives in the
spring 1993 season it was found that 'Jack of Hearts' and 'Crimson Sweet'
watermelon fruit had a low incidence and severity of hollowheart at 5 and 12 days
after pollination but much greater hollowheart at 19, 26, and 33 days after
pollination (Elmstrom et al., 1995).

Although useful, results from these studies did not provide conclusive evidence
on the effects of N and K rates on hollowheart or on the onset of hollowheart,
and additional research is needed.










NOTE

The information contained in this report is a summary of experimental results and
should not be used as recommendations for crop production. Where trade names are
used, no discrimination is intended and no endorsement is implied.

ACKNOWLEDGEMENT

This research was supported in part by a grant from the Florida Watermelon
Association, Marianna, FL 32447. Their support is appreciated.

LITERATURE CITED

Elmstrom, G. W., F. McCuistion, Jr., and D. N. Maynard. 1995. Incidence and
severity of watermelon (Citrullus lanatus) hollowheart. HortScience 30:427.

Hanlon, E. A., J. Gonzales, and J. M. Bartos. 1994. IFAS extension soil testing
laboratory chemical procedures and training manual. Fla. Coop. Ext. Serv. Circ.
812.

Hochmuth, G., D. Maynard, C. Vavrina, W. Stall, T. Kucharek, F. Johnson, and T.
Taylor. 1995. Cucurbit production in Florida: Cucumber, Muskmelon, Pumpkin,
Squash, Watermelon. p. 145-168 In D. N. Maynard and G. J. Hochmuth. Vegetable
production guide for Florida. Fla. Coop. Ext. Ser. SP 170.

Kano, Y. 1993. Relationship between the occurrence of hollowing in watermelon
and the size and number of fruit cells and intercellular air spaces. J. Japan.
Soc. Hort. Sci. 62:103-112.

McCuistion, F. T. Jr., G. W. Elmstrom, P. Abbott, B. Steinbach, B. Faile, N.
Ackerman, L. Neuwirth, and C. Spencer. 1995. Fluoroscopy as a non-invasive
method for detecting hollowheart and seeds in watermelon fruit. p 140-141 In. G.
E. Lester and J. R. Dunlap (eds.). Proceedings Cucurbitaceae '94. Gateway
Printing and Office Supply, Edinburg, TX 38539.

Stanley, C. D. 1994. Weather report for 1993. Gulf Coast Research and
Education Center Res. Rept. BRA1994-08.

U.S. Standards for Grades of Watermelons. 1978. USDA, AMS, Washington, D.C.










NOTE

The information contained in this report is a summary of experimental results and
should not be used as recommendations for crop production. Where trade names are
used, no discrimination is intended and no endorsement is implied.

ACKNOWLEDGEMENT

This research was supported in part by a grant from the Florida Watermelon
Association, Marianna, FL 32447. Their support is appreciated.

LITERATURE CITED

Elmstrom, G. W., F. McCuistion, Jr., and D. N. Maynard. 1995. Incidence and
severity of watermelon (Citrullus lanatus) hollowheart. HortScience 30:427.

Hanlon, E. A., J. Gonzales, and J. M. Bartos. 1994. IFAS extension soil testing
laboratory chemical procedures and training manual. Fla. Coop. Ext. Serv. Circ.
812.

Hochmuth, G., D. Maynard, C. Vavrina, W. Stall, T. Kucharek, F. Johnson, and T.
Taylor. 1995. Cucurbit production in Florida: Cucumber, Muskmelon, Pumpkin,
Squash, Watermelon. p. 145-168 In D. N. Maynard and G. J. Hochmuth. Vegetable
production guide for Florida. Fla. Coop. Ext. Ser. SP 170.

Kano, Y. 1993. Relationship between the occurrence of hollowing in watermelon
and the size and number of fruit cells and intercellular air spaces. J. Japan.
Soc. Hort. Sci. 62:103-112.

McCuistion, F. T. Jr., G. W. Elmstrom, P. Abbott, B. Steinbach, B. Faile, N.
Ackerman, L. Neuwirth, and C. Spencer. 1995. Fluoroscopy as a non-invasive
method for detecting hollowheart and seeds in watermelon fruit. p 140-141 In. G.
E. Lester and J. R. Dunlap (eds.). Proceedings Cucurbitaceae '94. Gateway
Printing and Office Supply, Edinburg, TX 38539.

Stanley, C. D. 1994. Weather report for 1993. Gulf Coast Research and
Education Center Res. Rept. BRA1994-08.

U.S. Standards for Grades of Watermelons. 1978. USDA, AMS, Washington, D.C.










NOTE

The information contained in this report is a summary of experimental results and
should not be used as recommendations for crop production. Where trade names are
used, no discrimination is intended and no endorsement is implied.

ACKNOWLEDGEMENT

This research was supported in part by a grant from the Florida Watermelon
Association, Marianna, FL 32447. Their support is appreciated.

LITERATURE CITED

Elmstrom, G. W., F. McCuistion, Jr., and D. N. Maynard. 1995. Incidence and
severity of watermelon (Citrullus lanatus) hollowheart. HortScience 30:427.

Hanlon, E. A., J. Gonzales, and J. M. Bartos. 1994. IFAS extension soil testing
laboratory chemical procedures and training manual. Fla. Coop. Ext. Serv. Circ.
812.

Hochmuth, G., D. Maynard, C. Vavrina, W. Stall, T. Kucharek, F. Johnson, and T.
Taylor. 1995. Cucurbit production in Florida: Cucumber, Muskmelon, Pumpkin,
Squash, Watermelon. p. 145-168 In D. N. Maynard and G. J. Hochmuth. Vegetable
production guide for Florida. Fla. Coop. Ext. Ser. SP 170.

Kano, Y. 1993. Relationship between the occurrence of hollowing in watermelon
and the size and number of fruit cells and intercellular air spaces. J. Japan.
Soc. Hort. Sci. 62:103-112.

McCuistion, F. T. Jr., G. W. Elmstrom, P. Abbott, B. Steinbach, B. Faile, N.
Ackerman, L. Neuwirth, and C. Spencer. 1995. Fluoroscopy as a non-invasive
method for detecting hollowheart and seeds in watermelon fruit. p 140-141 In. G.
E. Lester and J. R. Dunlap (eds.). Proceedings Cucurbitaceae '94. Gateway
Printing and Office Supply, Edinburg, TX 38539.

Stanley, C. D. 1994. Weather report for 1993. Gulf Coast Research and
Education Center Res. Rept. BRA1994-08.

U.S. Standards for Grades of Watermelons. 1978. USDA, AMS, Washington, D.C.








5
Table 1. Temperature and rainfall at the Gulf Coast Research and Education
Center, Bradenton from 21 March to 14 June 1995 and 40-year monthly
averages (Stanley, 1994).


Average daily temperature (OF)
1995 40-yr average Rainfall (in.)
Month' High Low High Low 1995 40-yr average

March (21-31) 83 61 77 55 2.57 3.35
April 83 63 82 60 3.41 1.72
May 91 70 87 64 1.48 3.20
June (1-14) 89 72 89 70 7.30 7.48

11995 data are for the dates shown, 40-year averages are .for the entire month.









Table 2. Yield, average fruit weight, soluble solids, and incidence and severity of hollowheart
Hearts' and 'Sangria' watermelon grown at variable N and K rates. Spring 1995.
Research & Education Center, Bradenton.


of 'Jack of
Gulf Coast


Treatment Yield Avg. Fruit Soluble Solids Hollowheart
N-P^20-K20 (cwt/acre) Wt (lb) (%) (%) (in.)
(Ib/acre) J of H Sangria J of H Sangria J of H Sanqria J of H Sangria J of H Sangria

130-60-180 559 c3 764 ab 12.7 c 18.9 b 11.1 a 11.0 a 26 a 3 b 0.37 a 0.01 b
320-60-180 582 bc 795 a 13.2 c 20.0 b 10.8 a 10.9 a 13 b 3 b 0.27 a 0.01 b
130-60-360 595 bc 581 bc 13.8 c 22.8 a 11.1 a 11.1 a 9 b 10 b 0.07 b 0.05 b
320-60-360 626 abc 616 abc 12.8 c 19.7 b 11.4 a 10.9 a 8 b 4 b 0.11 b 0.01 b


'Acre = 4840 linear bed feet.
2Diameter of fruit crack.
3Mean separation within parameters by Duncan's multiple range test, 5% level.










Table 3. Nitrogen and potassi
'Sangria' watermelon
rates. Spring 1995.
Bradenton.


um concentrations in 'Jack of Hearts' and
leaves from plants grown at variable N and K
Gulf Coast Research and Education Center,


Treatment N Concentration (% Dry Wt)
N-P205-K,0 8 May 24 May 6 June
(lb/acre) J of H Sangria J of H Sangria J of H Sangria

130-60-180 3.33 a2 3.87 a 4.86 a 4.86 a 5.66 a 5.61 a
320-60-180 3.43 a 4.21 a 5.04 a 4.67 a 6.16 a 5.61 a
130-60-360 3.76 a 3.42 a 5.00 a 4.85 a 6.18 a 6.29 a
320-60-360 3.67 a 4.13 a 5.10 a 4.72 a 6.09 a 5.45 a

K Concentration (% Dry Wt)

130-60-180 1.60 a 2.26 a 3.04 ab 2.72 b 4.07 a 3.50 a
320-60-180 1.71 a 2.32 a 3.51 a 2.97 ab 3.90 a 3.44 a
130-60-360 2.28 a 1.93 a 3.56 a 3.03 ab 3.98 a 4.17 a
320-60-360 1.81 a 2.37 a 3.37 a 3.10 ab 4.06 a 3.65 a


'Acre = 4840 linear bed feet.
2Mean separation within sampling dates and elements by Duncan's multiple range
test, 5% level.





Table 4. Diameter of 'Jack of Hearts' and 'Sangria' watermelon fruit and
incidence of hollowheart as related to fruit age. Gulf Coast
Research and Education Center, Bradenton.

Days Fruit Diameter (in.) Hollowheart (%)
After Jack of Jack of
Pollination Hearts Sanqria Hearts Sangria

5 3.3 3.3 0 0
10 4.5 4.0 11 0
15 7.4 6.4 0 0
20 8.2 6.6 0 0
25 8.5 7.3 0 0
30 9.5 7.9 25 0
35 10.0 7.7 0 17
Average -- 7 3







The Gulf Coast Research and Education Center


The Gulf Coast Research and Education Center is
a unit of the Institute of Food and Agricultural Sci-
ences, University of Florida. The Research Center
originated in the fall of 1925 as the Tomato
Disease Laboratory with the primary objective of
developing control procedures for an epidemic out-
break of nailhead spot of tomato. Research was ex-
panded in subsequent years to include study of sev-
eral other tomato diseases.

In 1937, new research facilities were established
in the town of Manatee, and the Center scope was
enlarged to include horticultural, entomological, and
soil science studies of several vegetable crops. The
ornamental program was a natural addition to the
Center's responsibilities because of the emerging in-
dustry in the area in the early 1940's.

The Center's current location was established in
1965 where a comprehensive research and extension
program on vegetable crops and ornamental plants is
conducted. Three state extension specialists posi-
tions, 16 state research scientists, and two grant
supported scientists from various disciplines of
training participate in all phases of vegetable and
ornamental horticultural programs. This interdisci-
plinary team approach, combining several research
disciplines and a wide range of industry and faculty
contacts, often is more productive than could be ac-
complished with limited investments in independent
programs.


The Center's primary mission is to develop new
and expand existing knowledge and technology, and
to disseminate new scientific knowledge in Florida, so
that agriculture remains efficient and economically
sound.

The secondary mission of the Center is to assist
the Cooperative Extension Service, IFAS campus
departments, in which Center faculty hold appropri-
ate liaison appointments, and other research centers
in extension, educational training, and cooperative
research programs for the benefit of Florida's pro-
ducers, students, and citizens.

Program areas of emphasis include: (1) genetics,
breeding, and variety development and evaluation;
(2) biological, chemical, and mechanical pest manage-
ment in entomology, plant pathology, nematology,
bacteriology, virology, and weed science; (3) produc-
tion efficiency, culture, management, and counteract-
ing environmental stress; (4) water management and
natural resource protection; (5) post-harvest physiol-
ogy, harvesting, handling and food quality of horti-
cultural crops; (6) technical support and assistance to
the Florida Cooperative Extension Service: and (7)
advancement offundamental knowledge ofdisciplines
represented by faculty and (8) directing graduate
student training and teaching special undergraduate
classes.


Location of
GCREC Bradenton


IFAS IS:
3 The Institute of Food and Agricultural Sciences,
University of Florida.
3 A statewide organization dedicated to teaching,
research and extension.
Z Faculty located in Gainesville and at 13 research
and education centers, 67 county extension
offices and four demonstration units throughout
the state.
Q A partnership in food and agriculture, and natural
and renewable resource research and education,
funded by state, federal and local government,
and by gifts and grants from individuals, founda-
tions, government and industry.
0 An organization whose mission is:
Educating students in the food, agricultural,
and related sciences and natural resources.
Strengthening Florida's diverse food and
agricultural industry and its environment
through research.
Enhancing for all Floridians, the application
of research and knowledge to improve the
quality of life statewide through IFAS exten-
sion programs.




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