Group Title: ARC-A research report - Agricultural Research Center-Apopka ; RH-80-11
Title: Guide for hybridizing Dieffenbachia
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Permanent Link: http://ufdc.ufl.edu/UF00065935/00001
 Material Information
Title: Guide for hybridizing Dieffenbachia
Series Title: ARC-A research report
Physical Description: 7 p. : ; 28 cm.
Language: English
Creator: Henny, R. J
Rasmussen, Eleanor M
Agricultural Research Center (Apopka, Fla.)
Publisher: University of Florida, IFAS, Agricultural Research Center-Apopka
Place of Publication: Apopka Fla
Publication Date: 1980
 Subjects
Subject: Dieffenbachia -- Breeding -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: R.J. Henny and Eleanor M. Rasmussen.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065935
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70913835

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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






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A GUIDE FOR HYBRIDIZING DIEFFENBACHIA

R. J. Henny and Eleanor M. Rasmussen
University of Florida, IFAS
Agricultural Research Center Apopka
ARC-A Research Report RH-80-11
At the Agricultural Research Center Apopka we have been studying th..e ."
breeding potential within the genus Dieffenbachia. Two goals of this program
are: A) The development of new and better varieties of Dieffenbachia for
commercial production in Florida and; B) To study the reproductive mechanisms
of Dieffenbachia and learn more of their biology and how it relates to all
tropical plants in general and other aroids in particular. Such research has
included studies of factors affecting plant growth, flowering, production and
storage of pollen and seed and inheritance of various plant traits (leaf and
petiole variegation, growth habit, etc.).
Currently, we have collected and are studying 50-60 distinct cultivars
of Dieffenbachia. Stock plants are grown in a medium consisting of 2 parts
Florida peat moss, 1 part cypress shavings and 1 part pine bark by volume.
This basic medium is amended with 7 Ibs dolomite, 3 Ibs perk and 10 Ibs Osmocote
(14-14-14) per cubic yard. In addition, plants receive 200 ppm of 20-20-20
liquid fertilizer biweekly. They are grown either in greenhouses or slat sheds
with light intensifies at 2500-3500 foot-candles. Temperatures are kept within
the limits of 65-950F throughout the year with the exception of the slat shed
which is allowed to cool to 45F during the winter. No apparent damage has been
observed on the-plants held at 450F and all of the cultivars and species of
Dieffenbachia have responded well to these growing conditions.
Under our conditions in central Florida, Dieffenbachia tend to have a
seasonal flowering hbait. There exists a spring "flush" of blooms during April,
May and June at which time most of our crosses are performed. Unfortunately,
some Dieffenbachia such as D. amoena flower in July and August while D. Oerstedii
flowers in the fall. Attempts to hybridize these plants with the earlier
flowering cultivars have been severely limited.
The Dieffenbachia inflorescence is made up of a spadix and a spathe. The
spadix consists of an upright central axis covered with several minute petalless
flowers. Staminate (male) flowers cover the upper half of the spadix and
pistillate (female) flowers are located on the basal half. Pistillate flowers
consist of a stigma, style and ovary while the staminate flowers are made up of





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the anther and filament and produce pollen. A pollination involves the transfer
of polled from selected staminate flowers to the stigmas of the selected
pistillate flowers.
The spathe covers the spadix until anthesis (the day of flower opening) at
which time it unfurls and exposes the staminate portion of the spadix. When-
ever possible the inflorescence should be pollinated the same day as the spathe
unfurls. Usually the spathe unfurls during the night so flowering plants should
be checked each morning for newly opened inflorescences; subsequent pollinations
may be made any time during the day of anthesis. Before a pollination can be
made a source of pollen must be found. The staminate flowers of Dieffenbachia
do not produce pollen until 2-3 days after the spathe unfurls. If fresh pollen
is not available, you can use pollen stored from inflorescences that opened
earlier. However, experimental results indicated that Dieffenbachia pollen does
not survive long in storage. Pollen was capable of good germination after 1 day
in storage at 770F (250C) or 410F (5C), but at 50F (-15C) germination was poor
(Table 1). After 2 days in storage germination was poor even in the best

Table 1. Germination of Dieffenbachia maculata 'Perfection' pollen after storage
at 3 different temperatures.

Length of Storage Temperature (OF)
Storage (Days) +77 +41 +5

0 1.6z 1.6 1.6
1 1.5 1.5 5.7
2 5.8 5.2 6.0
5 6.0 6.0 6.0

z 1 = excellent germination, 2 = good, 3 = moderate, 4 = fair, 5 = poor and
6 = none. 10 reps per treatment.

treatments and there was no germination in any treatment after 5 days in storage.
At 410F (50C) pollen stored the best at 90% relative humidity (Table 2). Moderate
germination occurred after 2 days of storage at 90% relative humidity compared to
poor or none at 50 and 10% relative humidity. After 5 days in storage there was
no germination at 10 or 50% relative humidity and poor germination at 90%. These
studies showed that Dieffenbachia pollen may be stored for only 1 day at 770F
(25C) or 410F (5C) if maintained at high (90%) relative humidity. One method
of storage would be to place the entire male portion of the spadix and its pi







Table 2. Germination of Dieffenbachia maculata 'Perfection' pollen after
storage at 410F (50C) and 3 different relative humidities,

Length of Relative Humidity (%)
Storage (Days) 10 50 90

0 1.7z 1.7 1.7
2 6.0 5.8 3.1
5 6.0 6.0 5.0

zl = excellent germination, 2 = good, 3 = moderate, 4 = fair, 5 = poor
and 6 = none. 10 reps per treatment.

in the bottom of a plastic cup, cover the cup with a damp cloth to increase the
relative humidity, and store the container in a refrigerator until use. A
razor blade may be used to cut off the male portion of the inflorescence. Use
of fresh pollen is desirable whenever possible.
When making a pollination a camel hair brush may be used to pick up the
pollen and transfer it to the stigmatic surface of the pistillate flowers. The
brush will pick up pollen easier if it is first brushed lightly across the moist
sticky surface of the stigma. The stigmatic surfaces of the pistillate flowers
may be identified by their golden yellow color and there may be 40-80 pistillate
flowers per inflorescence depending on the cultivar. The pistillate flowers are
surrounded by white apendages termed staminoidia which often extend higher than
the stigmatic surface. Staminoidia are sterile and serve no function during
pollination.
Recent studies concerning environmental effects on seed production in
Dieffenbachia have lead to methods of increasing seed yield. Tests have shown
that a critical factor affecting seed production in Dieffenbachia is the relative
humidity level at the time of pollination. It was demonstrated that seed are
rarely produced on inflorescences pollinated at a low relative humidity (of 40-50%
whereas a high percentage of inflorescences pollinated at a relative humidity)
near 100% will produce seed. Dieffenbachia maculata 'Perfection' was used as a test
plant in which 10 inflorescences were self-pollinated at low (40-50%) and at high
(100%) relative humidity. More than 56% of over 400 pistillate flowers on the 10
inflorescences pollinated at high relative humidity developed into seeds (Table
3). No seeds were produced on inflorescences pollinated at low relative









Table 3. In vivo pollen germination and seed set in Dieffenbachia maculata
'Perfection' inflorescences pollinated at low (40-50%) or high (100%)
relative humidity.


Inflorescence
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20


Relative
Humidity
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High


Pollen Germination
Rating
5.0z
1.0
5.0
1.0
5.0
1.0
5.0
1.0
5.0
1.0
4.0
1.0
5.0
1.0
5.0
1.0
5.0
1.0
5.0
1.0


No.
Ovariesy
32
34
36
51
44
48
25
39
26
33
41
49
46
40
45
48
52
41
35
48


No.
Seeds
0
26
0
30
0
37
0
10
0
17
0
39
0
27
0
36
0
6
0
20


Percent
Seed Set
0
76.5
0
58.8
0
77.1
0
25.6
0
51.5
0
79.6
0
67.5
0
75.0
0
14.6
0
41.7


ZNumber of pollen tubes observed. 1 = several, 2 = moderate amount, 3 = some,
4 = few, 5 = none. Mean of 10 styles per inflorescences.
YNumber of ovaries remaining per inflorescence after 10 harvested for observation
of pollen germination.

humidity. Microscopic examination of flowers following pollination revealed
there was no pollen germination on the stigmatic surface of flowers pollinated
at low relative humidity. Excellent pollen germination was observed on all
flowers pollinated at high relative humidity. Since pollen germination is the
first requirement for seed production, the lack of germination at low relative
humidity may be the reason for the poor seed yield often observed by people
attempting to breed Dieffenbachia. As mentioned earlier, most Dieffenbachia
tend to flower in the spring in central Florida. During this period, the
relative humidity may drop as low as 40-50% in greenhouses during the hottest
part of the day, especially during April and May, which drastically reduces
chances of seed production. As the more humid weather approaches in June and
July, seed production normally increases.








The negative effect of low relative humidity on seed production in
Dieffenbachia can be eliminated by using the following procedure. Newly
opened inflorescences are pollinated and the pistillate portion of the spadix
is then wrapped with a wet paper towel and the entire inflorescence enclosed
in a plastic bag. Increasing the relative humidity in this manner greatly
increases the chance of pollen germination and seed set. Using this method
we have been able to obtain consistent seed production from some cultivars
which had never yielded seed before.
In 3-4 weeks following a successful pollination, the pistillate flowers
(now technically a fruit) will turn green and begin to enlarge. During this
period the stigmas and the staminoidia will have deteriorated and disappeared.
As the fruits enlarge they change color from green to cream-colored to orange
to bright red when mature, approximately 4-5 months after pollination. The
fruits will not immediately fall off the spadix, once they have turned red,
although it is best to harvest them quickly.
Once harvested, mature fruit should be planted as soon as possible. Each
Dieffenbachia fruit generally contains 1 large seed and it is very important
not to let the seeds dry out or they will lose viability rapidly. Remove
the fleshy outer covering from the fruit before planting to help prevent
development of bacteria or fungi. After cleaning, seeds are soaked in a 10%
clorox solution for 5-10 minutes followed by a dip in a Benlate solution. Seeds
are then placed in small plastic trays on top of shallow depressions made in a
moistened medium consisting of 1 part German peat and 1 part perlite by volume
and amended with 3 Ibs dolomite and 1 lb Perk per cubic yard. Each container is
enclosed with a plastic bag to maintain the high relative humidity around the
seeds. The trays are placed under fluorescent lights which are on 12 hours
daily in growth rooms held at 800F. In 3-4 weeks the seeds have germinated and
the plastic cover is removed. When seedlings have produced 4-5 leaves they are
transplanted into 4 inch pots containing the same medium used for germination.
Seedlings are finally repotted into 6 inch pots using our normal 2:1:1 medium.
Although research has shown how to pollinate, store pollen and increase seed
production, breeding of Dieffenbachia has been limited by sporadic flowering and
the small number of inflorescences per plant. However, experiments with the
plant hormone gibberellic acid (GA3) have made it possible to stimulate flowering
in Dieffenbachia and increase the number of inflorescences per plant. Initial
studies were conducted using full-sized 6 inch pots of Dieffenbachia maculata
'Perfection'. Plants were sprayed once on both the upper and lower leaf surfaces





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until runoff with GA3 in September, 1979. Ten plants were sprayed at each
concentration of 0, 250, 500 and 1000 ppm. Plants receiving 0 ppm GA3 were
sprayed with water. During the course of this study, the plants were
maintained in a greenhouse with a 65-90F temperature regime.
All treated plants produced visible flower buds within 8 weeks after being
sprayed and all had at least 1 open inflorescence within 13 weeks. In the
same time period none of the control plants showed any evidence of flower
formation. Dieffenbachia maculata 'Perfection' plants normally produce 3 to 5
inflorescences at flowering. In this experiment plants produced a mean of 6.6,
8.7 and 9.3 inflorescences when treated with 250, 500 and 1000 ppm GA3
respectively (Table 4). Some plants produced as many as 12 inflorescences.

Table 4. Effect of gibberellic acid (GA3) sprays on the number of days to
flower and number of inflorescences per plant of Dieffenbachia maculata
'Perfection'.

GA3 conc. Mean Days to Mean Number of
(ppm) First Bloomz Inflorescences
0-Y -
250 92.7X 6.6
500 89.6 8.7
1000 91.8 9.3

ZDay the first inflorescence opened.
YPlants did not flower before experiment terminated at 150 days. Plants
were sprayed September 17, 1979.
10 reps per treatment.


Inflorescences were normal in appearance and were fertile. GA3 has been used
successfully on several cultivars of Dieffenbachia and, even small seedlings with
6-8 leaves have been induced to flower.
Results of this study have important implications for anyone breeding
Dieffenbachia. Plants that would not normally flower until the spring now may
be induced to flower 4 to 5 months earlier by GA3 applications during early fall.
Plants would not have to be "held" through the winter waiting for the spring
bloom. It may be possible to maintain blocks of plants in bloom at different
times throughout the year to spread out the period of pollination. Seeds
maturing during the winter and harvested in the spring will germinate and grow








faster during the warm summer season. Until this time, seeds harvested in
the fall, once germinated, make little growth during the winter due to
cooler temperatures. Overall, this allows for much greater flexibility in
a breeding program, shortens dramatically the life cycle and permits faster
development of hybrid plants. Further tests are being conducted with GA3
and its effects on flowering of Dieffenbachia throughout the year. Preliminary
results indicate that visible flower buds appear within 6 weeks following
application of GA3 in June (experiment in progress).
This is a current summary of research involved with breeding Dieffenbachia.
It is hoped that this report will both stimulate and encourage people to make
use of the genetic variability contained in this genus through hybrid
production.







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