GCREC Research Report BRA2003-

TRIPLOID MINI WATERMELON CULTIGEN EVALUATION

D. N. Maynard² and B. J. Sidoti³,

Gulf Coast Research and Education Center

University of Florida

5007 60^th Street East

Bradenton, FL 34203

Diploid (seeded) watermelons generally weigh from 18 to 35 lb and represent about 40% of the commercial crop grown in Florida. Triploid (seedless) watermelons usually weigh 15 to 22 lb and account for about 60% of the shipments from Florida. The proportion of the Florida crop devoted to triploid production is increasing each year. Icebox watermelons weigh 6 to 12 lb each and are grown on a very small acreage. Triploid personal size or miniwatermelons were introduced in 2003; these fruit weigh 3 to 7 lb. each. Production is expected to increase. Florida produced 8.6 million cwt of watermelons of all types from 24,000 harvested acres in 2000-2001, which provided an average yield of 310 cwt/acre. The average price was $5.70/cwt resulting in a crop value of over $42 million which accounted for 2.5% of the gross value of the state’s vegetable crops (Fla. Agr. Stat. 2002).

Specialty vegetables are in high demand and seedless miniwatermelons offer an attractive alternative for discriminating consumers. Seedless miniwatermelons are being actively promoted by marketing organizations and seed companies to stimulate demand. At the same time, many new varieties are being developed and introduced.

The objective of this trial was to evaluate the performance of triploid miniwatermelon cultigens under west-central Florida conditions.

Seeds of nine triploid miniwatermelon varieties or experimental hybrids (Table 1) were planted in a peat-lite growing mix in planter flats (1 ¼ x 1 ¼ x 2 ¼ in. cells) on 4 February. The watermelon transplants were grown by a commercial plant grower.

The EauGallie fine sand was prepared in mid February. Beds were formed and fumigated with methylbromide:chloropicrin, 67:33 at 350 lb/treated acre. Banded fertilizer was applied in shallow grooves on the bed shoulders after the beds were pressed and before the black polyethylene mulch was applied. The total fertilizer applied was equivalent to 150-40-208 lb N-P₂O₅-K₂O/A. The final beds were 32-in. wide and 8-in. high, and were spaced on 5-ft centers with six beds between seepage irrigation/drainage ditches, which were on 41-ft centers.

The transplants were set in holes punched in the polyethylene mulch on 11 March at 2.5-ft in-row spacing that provided 12.5 ft²/plant. The replicated plots were 20 ft long and had eight plants each and were repeated four times in a randomized, complete block design. ‘Summer Flavor 800’ diploid watermelon transplants were planted in every fourth hole to serve as the diploid pollenizer. Plant stands 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 gummy stem blight (chlorothalonil, azoxystrobin, mancozeb, and maneb), and lepidopterous larvae and silverleaf whitefly (Bacillus thuringiensis, endosulfan, bifentrin, potassium salts of fatty acids, and spinosad).

Watermelons were harvested on 22 and 30 May. 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. Six fruit from each entry were used to determine soluble solids (a measure of sweetness) with a digital, hand-held refractometer, polar and equatorial dimensions, rind thickness, flesh color, and the incidence and severity of hollowheart. Where possible, data were subjected to analysis of variance and mean separation was by Duncan’s multiple range test.

Maximum temperatures were near normal and minimum temperatures were above average throughout the growing period. This resulted in an earlier than usual crop. Rainfall was less than normal throughout the period.

Yield data calculations did not include the ‘Summer Flavor 800' pollenizer area, but were determined as if the miniwatermelons were planted on the entire acre. Yield data are presented in three formats based on individual fruit weight: 4 to 6 lb.; 3-7 lb.; and 3-8 lb. because there are no generally agreed weight parameters for minimelons. Accordingly, one can select the weight range of most interest.

Fruit number per acre of 4-6 lb. fruit varied from 1924 for ‘Bambino’ to 6861 for ‘Vanessa’ while weight per acre ranged from 96 cwt/acre for ‘Bambino’ to 349 cwt/acre for ‘Vanessa’ (Table 2). Average fruit weight was similar among all entries. Fruit per plant varied from 0.6 for ‘Bambino’ to 2.0 for ‘Vanessa’.

For fruit in the 3-7 lb. weight class, fruit per acre ranged from 4102 for ‘Bambino’ to 10,128 for ZG 8905 (Table 3). On the basis of weight, yields varied from 220 cwt/acre for ‘Bambino’ to 514 cwt/acre for ‘Vanessa’. Average fruit weight varied from 4.9 lb for ZG 8905 to 5.9 lb for ‘Extazy’. Fruit per plant ranged from 1.2 for ‘Bambino’ to 2.9 for ZG 8905 and ‘Vanessa’.

For fruit in the 3-8 lb. class, fruit per acre varied from 4901 for ‘Bambino’ to 11,217 for ‘Vanessa’ (Table 4). Weight ranged from 277 cwt/acre for ‘Bambino’ to 604 cwt/acre for ‘Vanessa’. Average fruit weight varied from 5.0 for ZG 8905 to 6.4 for ‘Extazy’. Fruit per plant ranged from 1.4 for ‘Bambino’ to 3.2 for ‘Vanessa’.

Regardless of weight parameters (Tables 2, 3, 4), ‘Vanessa’, ‘Petite Perfection’, ZG 8905, and RWT 8149 proved to be the highest yielding minimelons in this trial. SR 8102WM, although producing acceptable yields, must be disqualified because many fruit were found to contain seeds and the rind was extremely brittle.

Soluble solids (Table 5) varied from 11.4% for ZG 8905 to 14.4% for ‘Petite Perfection’. 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). Hollowheart did not vary among the entries although minor all separations were noted in ‘Bambino’, RWT 8149, SR 8102WM, SR 8103WM, and ZG 8905 (Table 5).

If 3-9 lb. is considered to be the acceptable weight for minimelons, then a very high proportion of RWT 8149 (98%), ‘Vanessa’ (98%), ‘Petite Perfection’ (97%), ‘Extazy’ (92%) fruit were in the acceptable minimelon weight range (Table 6). A high proportion, 20% or more of SR 8102WM, ZG 8905, SR 8103WM, and ‘Bambino’ fruit did not fall in the 3-9 lb. range. If 3-7 lb. minimelons are desired, RWT 8149 (75%), ZG 8905 (76%), ‘Vanessa’ (80%), and ‘Petite Perfection’ (81%) produced a high proportion of fruit in this weight class.

Triploid minimelons are an exciting new class of watermelons that are of special interest to one to two person households, households with children, and occasional watermelon consumers. It is likely that they will become a permanent segment of the watermelon market, but its size is difficult to estimate at this time. Outstanding entries in this trial were ‘Petite Perfection’, and ‘Vanessa’.

The information contained in this report is a summary of experimental results. No discrimination is intended and no endorsement is implied where trade names are used.

We are grateful to the following firms for their financial and material support of vegetable variety evaluation during 2002-2003. Abbott & Cobb; Agrisales, Inc.; BHN Research; Fafard Inc.; Harris Moran Seed Co.; Hazera Quality Seeds; Hollar Seeds; Sakata Seed America; Shamrock Seed Co.; Seminis Vegetable Seeds, Inc.; Southwestern Vegetable Seed Co.; Sugar Creek Seeds, Inc.; Sunseeds; Syngenta Seeds; U.S. Seedless, LLC; Willhite Seed, Inc.; and Zeraim Gedera Ltd.

LITERATURE CITED

Florida Agricultural Statistics Service. 2002. Vegetables, acreage, production, value. Orlando, Fla.

U. S. Dept. Agr. 1978. U.S. standards for grades of watermelons. AMS, Washington, D.C.