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GCREC Research Report BRA 1998-08
TRIPLOID WATERMELON CULTIGEN EVALUATION
SPRING 1998
D. N. Maynard' and A. V. Wittman2
Gulf Coast Research and Education Center
University of Florida, IFAS
5007 60th Street East
Bradenton, FL 34203
The concept oftriploid (seedless) watermelons was described first in the U.S. literature by Kihara
(1951) based on experimentation that began in 1939 in Japan. Seed for planting seedless
watermelons results from a cross between a selected tetraploid female parent, developed by treating
diploid lines with colchicine, and a selected diploid (normal) male parent. The resulting triploid
plants are sterile and do not produce viable seed. However, small, white rudimentary seeds develop
which are eaten along with the flesh just as immature seeds are eaten in cucumber.
Fruit enlargement in normal fruit, including watermelon, is enhanced by growth-promoting
hormones produced by the developing seed. Growth hormones are lacking in seedless watermelons
so those agents must be provided by pollen. Since flowers on triploid plants lack sufficient viable
pollen to induce normal fruit set, normal diploid seeded watermelons are interplanted with triploids
to serve as pollenizers. An adequate bee population is necessary to insure that sufficient transfer of
pollen occurs. Seedless fruit (from triploid plants) tend to be triangular shaped without sufficient
pollination.
Although the procedure for production of seedless watermelons has been known for almost 50 years
and commercial varieties have been available for over 20 years, the interest in and acreage of
seedless watermelons has remained relatively small in Florida. Erratic performance, poor seed
germination, high seed costs, and inadequate varieties resulted in the lack of interest in seedless
watermelon production in the past.
Specialty vegetables are in high demand and seedless watermelons offer an attractive alternative for
discriminating consumers and the food service industry. Seedless watermelons are being actively
promoted by marketing organizations and seed companies to stimulate demand. At the same time,
new varieties are being developed that are superior to those previously available. Seedless
watermelons have been evaluated at this location annually since 1988 (Maynard and Gilreath, 1988;
Maynard 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997).
1Professor.
2Laboratory Technician.
August
The objective of this trial was to evaluate the performance of triploid watermelon cultigens under
west-central Florida conditions.
MATERIALS AND METHODS
Seeds of 21 triploid watermelon varieties or experimental lines (Table 1) were planted in a peat-lite
growing mix in No. 128 Todd planter flats (1.5 x 1.5 x 2.5 in. cells) on 21 January. The watermelon
transplants were grown by a commercial plant grower.
Soil samples from the experimental area obtained before fertilization were analyzed by the
University of Florida Extension Soil Testing Laboratory (Hanlon and DeVore, 1989): pH = 7.2 and
Mehlich I extractable P = 130 (very high), K = 13 (very low), Mg = 80 (high), Ca = 827 (adequate),
Zn = 9.6 (adequate), Cu = 4.6 (adequate), and Mn = 5.9 (adequate) ppm.
The EauGallie fine sand was prepared in late January by incorporation of 0-1.2-0 lb. N-P205-K20 per
100 linear bed feet (lbf). Beds were formed and fumigated with methylbromide:chloropicrin, 67:33
at 2.3 lb/100 lbf. Banded fertilizer was applied in shallow grooves on the bed shoulders at 3.1-0-4.3
lb N-P205-K20/100 lbf after the beds were pressed and before the black polyethylene mulch was
applied. The total fertilizer applied was equivalent to 148-60-206 lb N-P205-K20/A. 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.
Transplant return, the percentage of seeds that developed into acceptable transplants, was determined
for each entry. The transplants were set in holes punched in the polyethylene at 3 ft in-row spacing
on 26 February. The replicated plots were 30 ft long and had ten plants each and were repeated three
times in a randomized, complete block design. Diploid watermelons that were being evaluated were
direct seeded in beds on each side of two triploid watermelon beds on 13-17 February to serve as
diploid pollenizers. Plant stand counts recorded just before vines grew together showed no
significant differences among plots. Weed control in row middles was by cultivation and
applications of paraquat. Pesticides were applied as needed for control of silverleaf whitefly
endosulfann), gummy stem blight (chlorothalonil, metalaxyl-chlorothalonil, alliette, and maneb),
bacterial fruit blotch (fixed copper), and worms (Bacillus thuringiensis and methomyl).
Watermelons were harvested on 4 June and 9-15 June. Marketable (U.S. No. 1 or better) fruit
according to U.S. Standards for Grades of Watermelons (U.S. Dept. Agr., 1978) were separated
from culls and counted and weighed individually. Fruit 8 lbs and larger were assumed to be
marketable. Tetraploid fruit, where they occurred, were not included in the marketable category
because they are not seedless. Soluble solids (a measure of sweetness) were determined with a
hand-held refractometer on at least six fruit from each entry at each harvest and the incidence and
severity of hollowheart were noted on these fruit. Cell separations however slight were noted as
hollowheart, even though the fruit may be commercially acceptable. Where possible, the resulting
data were subjected to analysis of variance and mean separation was by Duncan's multiple range test.
RESULTS AND DISCUSSION
Temperature (Table 2) during the experimental period from 26 February to 15 June was near normal
in March, April, and May, the principal growing months. Rainfall was over twice normal in March,
only 0.10 inch in April, and sparce in early June. Strong and persistent winds in March caused
considerable vine twisting on the polyethylene mulch.
Transplant return, the proportion of usable transplants obtained of seeds planted, ranged from 53%
in 'Sterling' to 97% in FS 4502 (Table 3). Differences in seed performance may be related to seed
quality as influenced by production techniques, seed storage, or characteristics of the individual
hybrid.
Early yield, as represented by the first of two harvests, varied from 273 cwt/acre for 'Sterling' to 607
cwt/acre for 'Tri-X-Shadow' (Table 3). Eleven other entries had yields similar to those of 'Tri-X-
Shadow' and 17 other entries had early yields statistically similar to 'Sterling'. Average fruit
weights at the first harvest ranged from 13.2 lbs for HMX 7928 to 20.9 lbs for 'Sterling'. Soluble
solids concentrations varied from 11.6% in RWM 8073 to 13.8% in 'Tri-X-Carousel' at the first
harvest. The percentage of fruit having hollowheart at the first harvest ranged from 0 in 'Tri-X-
Shadow' and 'Tri-X-Palomar' to 100% in 'Sapphire'.
Total yields (Table 3) ranged from 498 cwt/acre for 'Sterling' to 846 cwt/acre for 'Millionaire'.
Only three entries produced yields significantly lower than 'Millionaire'. Average fruit weight for
the entire season varied from 12.7 lbs for HMX 6910 and HMX 7928 to 18.8 lbs for 'Sterling'.
Soluble solids concentrations varied from 11.9% for FS 4502 to 13.3% for 'Tri-X-Carousel'.
Accordingly, soluble solids in all entries far exceeded the 10% specified for optional use in the U.S.
Standards for Grades of Watermelons to describe very good internal quality (U.S. Dept. Agr., 1978).
The incidence of hollowheart ranged from 0 in 'Tri-X-Palomar' to 58% in 'Sapphire'. There was
no statistical difference in hollowheart severity among the entries.
The distribution of fruit into weight classes is shown in Table 4. When triploid fruit are packed in
cartons, there is an advantage in having a high proportion of fruit in the 14 to 18 lb category.
'Revolution' and 'Millionaire' produced 42% and 40% of their fruit in this weight range in contrast
to 95-11 where only 21% of the fruit were between 14 and 18 lbs. Fruit are graded into two or more
sizes when they are shipped in bins. Large fruit are useful for food service or as a precut product.
For example, 'Sterling' produced 42% of its fruit weighing more than 18 lbs whereas only 12% of
'Sapphire' fruit exceeded 18 lbs.
SUMMARY
Seedless watermelon variety trials have been conducted at this location each spring season since
1988. The highest yields ranged from 507 cwt/A in 1996 to 1161 cwt/A in 1993 (Maynard, 1993,
1996). In spring 1998, the highest yield was 846 cwt/A which was somewhat more than the 763
cwt/A average high yield of the previous ten years.
Variety shape and rind patterns, based on observations in this trial, are shown in Table 1. Varieties
producing oval to oblong fruit may be more suitable for boxing than varieties producing round
melons. Generally, the striped melons are more attractive for the U.S. market than those with dark
stripes on a very dark green background, or those with a solid dark green rind.
Based on results of this and previous trials, triploid hybrids, in alphabetical order, that should
perform well in Florida include 'Constitution', 'Crimson Trio', 'Freedom', 'Genesis', 'King of
Hearts', 'Millionaire', 'Revere', 'Scarlet Trio', 'Summersweet 5244', 'Summersweet 5544', and
'Tri-X-313'. Other varieties may perform well on individual farms.
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.
ACKNOWLEDGMENT
The authors appreciate the financial support for watermelon variety evaluation provided by Abbott
& Cobb, Inc., American Sunmelon, Asgrow Seed Co., Florida Seed Co., Inc., Harris Moran Seed
Co., Hollar Seeds, Novartis Seeds, Inc., Sakata Seed America, Inc., Shamrock Seed Co., Sunseeds
Co., and Willhite Seeds, Inc.
LITERATURE CITED
Hanlon, E. A. and J. M. DeVore. 1989. IFAS extension soil testing laboratory chemical procedures
and training manual. Fla. Coop. Ext. Circ. 812.
Kihara, H. 1951. Triploid watermelons. Proc. Amer. Soc. Hort. Sci. 58:217-230.
Maynard, D. N. 1989. Seedless watermelon variety evaluation, spring 1989. Gulf Coast Research
and Education Center Res. Rept. BRA1989-16.
Maynard, D. N. 1990. Seedless watermelon variety evaluation, spring 1990. Gulf Coast Research
and Education Center Res. Rept. BRA1990-14.
Maynard, D. N. 1991. Seedless watermelon variety evaluation, spring 1991. Gulf Coast Research
and Education Center Res. Rept. BRA 1991-21.
Maynard, D. N. 1992. Seedless watermelon variety evaluation, spring 1992. Gulf Coast Research
and Education Center Res. Rept. BRA1992-18.
5
Maynard, D. N. 1993. Seedless watermelon cultigen evaluation, spring 1993. Gulf Coast Research
and Education Center Res. Rept. BRA1993-18.
Maynard, D. N. 1994. Seedless watermelon cultigen evaluation, spring 1994. Gulf Coast Research
and Education Center Res. Rept. BRA 1994-21.
Maynard, D. N. 1995. Seedless watermelon cultigen evaluation, spring 1995. Gulf Coast Research
and Education Center Res. Rept. BRA 1995-24.
Maynard, D. N. 1996. Seedless watermelon cultigen evaluation, spring 1996. Gulf Coast Research
and Education Center Res. Rept. BRA1996-17.
Maynard, D. N. 1997. Triploid watermelon cultigen evaluation, spring 1997. Gulf Coast Research
and Education Center Res. Rept. BRA1997-15.
Maynard, D. N. and P. R. Gilreath. 1988. Seedless watermelon variety evaluation, spring 1988.
Gulf Coast Research and Education Center Res. Rept. BRA1988-18.
Stanley, C. D. 1998. Weather report for 1997. Gulf Coast Research and Education Center Res.
Rept. BRA1998-02
U.S. Dept. Agr. 1978. U.S. Standards for Grades of Watermelons. AMS, Washington, D.C.
Triploid watermelon entries, fruit descriptions, and seed sources. Gulf Coast
Research & Education Center, Bradenton. Spring 1998.
Entry Description Source
Constitution
(SXW 3053)
Crimson Trio
Freedom
(SXW 3022)
FS 4502
Gem-Dandy
Genesis
HMX 7928
HMX 6910
Millionaire
Revolution
(SXW 4034)
RWM 8073
Blocky. Indistinct wide medium green-stripes
on light-green background. Similar to
'Tiffany'.
Oval. Indistinct wide medium-green stripes on
light-green background. Similar to 'Tri-X-
313'.
Elongated/blocky. Distinct dark-green stripes
on light-green background. 'Jubilee' type.
Blocky/oval. Indistinct, wide medium-green
stripes on light-green background. Similar to
'Tri-X-313'.
Oval. Indistinct wide medium-green stripes on
light-green background. Similar to 'Tri-X-
313'.
Oval. Indistinct, wide dark-green stripes on
light-green background. Similar to 'Tri-X-
313'.
Oval. Indistinct, very dark-green stripes on
dark-green background. Similar to 'Sugar
Baby'.
Blocky. Distinct dark-green stripes on light-
green background. Similar to 'Queen of
Hearts'.
Oval. Indistinct, wide dark-green stripes on
light-green background. Similar to 'Tri-X-
313'.
Elongated. Wide dark-green stripes alternating
with narrow light-green stripes. 'Allsweet'
type.
Oval. Distinct medium-green stripes on light-
green background. Similar to 'Tri-X-313'.
Sunseeds
Novartis
Sunseeds
Florida Seed
Willhite
Shamrock
Harris Moran
Harris Moran
Harris Moran
Sunseeds
Novartis
Table 1.
Entry Description Source
Sapphire
SSC 46072
Sterling (HSR 1599)
Tri-X-Carousel
Tri-X-Palomar
Tri-X-Shadow
Tri-X-313
XWM 7703
95-11
95-14
Oval. Distinct wide medium-green stripes on
light-green background. Similar to 'Tri-X-
313'.
Oval/round. Indistinct wide medium-green
stripes on light-green background. Similar to
'Tri-X-313'.
Blocky/oblong. Indistinct wide medium-green
stripes on light-green background. 'Allsweet'
type.
Oval. Broad green stripes on light-green
background. Similar to 'Tri-X-313'.
Round. Indistinct narrow dark-green stripes
on medium-green background.
Round/oval. Distinct dark-green stripes on
medium-green background.
Oval. Indistinct, broad medium-green stripes
on light-green background.
Oval/blocky. Indistinct wide dark-green stripes
on light-green background. Similar to 'Tri-X-
313'.
Blocky/oval. Narrow, distinct dark-green
stripes on light-green background. Similar to
'Queen of Hearts'.
Oval. Wide, indistinct dark-green stripes on
light-green background. Similar to 'Tri-X-
313'.
Hollar
Shamrock
Hollar
American Sunmelon
American Sunmelon
American Sunmelon
American Sunmelon
Sakata
Sakata
Sakata
Table 2.
Temperature and rainfall at the GCREC during the spring of 1998 and the 43-year
averages (Stanley, 1998).
Average Daily Temperature (*F)
Maximum Minimum Rainfall (in.)
Month 1998 43-yr avg 1998 1 43-yr avg 1998 43-yr avg
February 80 74 57 52 0.02 2.96
March 76 78 54 55 8.16 3.37
April 82 82 59 60 0.10 1.78
May 88 87 64 65 3.41 3.24
June 93 90 74 70 0.32 7.69
1Field transplanted 26 February 1998. Last harvest 15 June 1998.
Table 3. Early and total yields, transplant return ,average fruit weight, soluble solids and the incidence and severity of hollowheart of triploid
watermelons. Gulf Coast Research and Education Center, Bradenton. Spring 1998.
Early Harvest1 Total Harvest
Transplant Avg. Soluble Avg. Fruit Soluble
Return Weight Weight Solids Hollowheart Weight Weight Solids Hollowheart
Entry (%) (cwt/A)2 (Ib) (%) (%) (in.)3 (cwt/A)2 (Ib) (%) (%) (in.)3
Millionaire 70 534 abs 17.3 bc 13.0 a-c 17 bc 0.2 a 846 a 15.9 b-e 12.7 a-d 77 a-c 0.2 a
Tri-X-313 84 511 a-c 18.5 ab 12.7 a-d 50 a-c 0.5 a 820 ab 16.3 b-d 12.8 a-d 33 a-c 0.3 a
Tri-X-Shadow 77 607 a 16.2 b-e 13.1 a-c 0 c 0 a 791 ab 15.2 b-e 12.9 a-c 8 bc 0 a
Crimson Trio 81 461 a-c 17.2 b-d 13.0 a-c 50 a-c 0.4 a 781 a-c 15.4 b-e 12.7 a-d 25 a-c 0.2 a
FS 4502 97 542 ab 18.7 ab 12.3 b-d 33 a-c 0.1 a 756 a-c 16.7 b 11.9 d 17 a-c 0.1 a
------------------------------------------------------------------------------------------------------------------------
95-11 91 460 a-c 16.3 b-e 12.4 b-d 33 a-c 0.1 a 731 a-c 14.2 d-f 12.5 a-d 33 a-c 0.3 a
Freedom 84 337 bc 16.4 b-e 12.9 a-c 50 a-c 1.6 a 725 a-c 14.9 b-e 13.0 a-c 50 ab 0.9 a
95-14 83 341 bc 16.6 b-d 13.5 ab 50 a-c 0.5 a 706 a-c 14.6 b-f 13.2 ab 50 ab 0.9 a
Gem-Dandy 69 380 a-c 18.0 ab 12.7 a-d 50 a-c 0.8 a 673 a-c 15.4 b-e 12.2 b-d 25 a-c 0.4 a
Tri-X-Palomar 70 387 a-c 16.1 b-e 12.4 b-d 0 c 0 a 669 a-c 14.4 c-f 12.6 a-d 0 c 0 a
-----------------------------------------------------------------------------------------------------------------------
Tri-X-Carousel 93 472 a-c 18.0 ab 13.8 a 50 a-c 0.3 a 664 a-c 16.7 b 13.3 a 42 a-c 0.4 a
HMX 6910 46 335 bc 14.0 de 12.2 b-d 83 ab 1.7 a 662 a-c 12.7 f 12.4 a-d 33 a-c 0.8 a
SSC 46072 60 349 bc 17.7 b 12.2 b-d 50 a-c 0.5 a 649 a-c 15.2 b-e 12.3 a-d 42 a-c 0.6 a
Sapphire 87 338 bc 15.7 b-e 13.3 a-c 100 a 1.7 a 648 a-c 13.8 ef 12.9 a-c 58 a 0.9 a
HMX 7928 60 458 a-c 13.2 e 12.8 a-d 50 a-c 1.7 a 646 a-c 12.7 f 12.7 a-d 33 a-c 1.0 a
-----------------------------------------------------------------------------------------------------------------------
XWM 7703 56 382 a-c 15.7 b-e 12.9 a-d 33 a-c 0.9 a 631 a-c 14.1 d-f 12.5 a-d 25 a-c 0.5 a
RWM 8073 NA4 313 bc 17.8 ab 11.6 d 67 a-c 0.8 a 609 a-c 16.4 bc 12.5 a-d 42 a-c 0.5 a
Constitution 88 374 a-c 15.4 b-e 12.2 cd 67 a-c 0.7 a 605 a-c 14.6 b-f 12.9 a-c 50 ab 0.4 a
Genesis 90 344 bc 14.3 c-e 12.4 b-d 17 bc 0 a 545 bc 13.6 ef 12.4 a-d 17 a-c 0.1 a
Revolution 63 361 bc 16.3 b-e 13.0 a-c 33 a-c 0.1 a 545 bc 15.6 b-e 12.6 a-d 25 a-c 0.1 a
------------------------------------------------------------------------------------------------------------------------
Sterling 53 273 c 20.9 a 12.3 b-d 50 a-c 0.8 a 498 c 18.8 a 12.1 cd 42 a-c 0.9 a
'Early harvest based on first of two harvests.
2Acre = 4840 Ibf.
3Average separation of those fruit sampled.
4Not available.
5Mean separation in columns by Duncan's multiple range test, 5% level.
10
Table 4. Fruit weight distribution of the total yield of triploid watermelons. Gulf Coast
Research and Education Center, Bradenton. Spring 1998.
Fruit Weight (Ib)
Entry 8.0-14.0 14.1-18.0 18.1-22.0 > 22.0
--------------------Percentage of fruit----------------
Constitution (SXW 3053)
Crimson Trio
Freedom (SXW 3022)
FS 4502
Gem-Dandy
Genesis
HMX 7928
HMX 6910
Millionaire
Revolution (SXW 4034)
RWM 8073
Sapphire
SSC 46072
Sterling (HSR 1599)
Tri-X-Carousel
Tri-X-Palomar
Tri-X-Shadow
Tri-X-313
XWM 7703
95-11
95-14
53
35
49
57
68
72
33
37
36
60
46
35
30
50
46
33
56
58
26 15
35 8
23 9
23 4
40 20
42 14
30 23
28 11
31 17
24 18
36 23
36 12
25 28
34 24
31 11
21 17
7
6
9
10
10
0
1
1
6
8
10
1
6
24
11
2
1
9
2
4
7
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.
Location of
GCREC Bradenton
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 of fundamental knowledge of disciplines
represented by faculty and (8) directing graduate
student training and teaching special undergraduate
classes.
IFAS IS:
I The Institute of Food and Agricultural Sciences,
University of Florida.
A statewide organization dedicated to teaching,
research and extension.
Faculty located in Gainesville and at 13 research
and education centers, 67 county extension
offices and four demonstration units throughout
the state.
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.
i 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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