DIPLOID WATERMELON VARIETY EVALUATION

SPRING 2003¹

 

D. N. Maynard² and B. J. Sidoti³

Gulf Coast Research and Education Center

University of Florida

5007 60^th Street East

Bradenton, FL 34203

 

 

‘Allsweet’ and blocky ‘Crimson Sweet’ hybrids are the most commonly grown diploid watermelons in Florida. 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. Icebox watermelons weigh 6 to 12 lb each and are grown on a very small acreage. Personal size watermelons were introduced in 2003; these fruit weigh 3 to 7 lb. each. 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).

The purpose of this trial was to evaluate commercial and experimental hybrids of the blocky >Crimson Sweet= and >Allsweet= types.

 

Materials and Methods

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 = 6.1 (target pH is 6.0) and Mehlich I extractable P = 133 ppm (very high), K = 12 ppm (very low), Mg = 52 ppm (high), Ca = 725 ppm (adequate), Zn = 12.3 ppm (adequate), Cu = 5.6 ppm (adequate), and Mn = 6.1 ppm (adequate).

The EauGallie fine sand was prepared in early February by incorporation of 0-0.8-0 lb N-P₂O₅-K₂O per 100 linear bed feet (lbf). Beds were formed and fumigated with methyl bromide:chloropicrin, 67:33 at 2.45 lb/100 lbf. Banded fertilizer was applied in shallow grooves on bed shoulders at 3.1-0-4.3 lb N-P₂O₅-K₂O/100 lbf after the beds were pressed and before application of the black polyethylene mulch. Total fertilizer applied was equivalent to 150-40-208 lb N-P₂O₅-K₂O/acre. The final beds were 32-in. wide and 8-in. high and were spaced on 9-ft centers (4840 lbf/acre), with four beds between seepage irrigation/drainage ditches which were on 41-ft centers. The diploid watermelons were planted in rows adjacent to the ditches and also served as pollenizers for triploid watermelons that were being evaluated in the two center beds of each land.

Watermelon seeds were planted on 26 February in holes punched in the polyethylene mulch at 3-ft in-row spacing. Seedlings were thinned at the two true-leaf stage to one per hole. Twenty-seven entries (Table 1) were included in the trial. The 30-ft long plots had ten plants each and were replicated four times in a randomized complete-block design. Weed control in row middles was accomplished by cultivation and application of paraquat. Plant stands recorded just before vines grew together showed no significant difference among plots. Pesticides were applied as needed for control of gummy stem blight (chlorothalonil, mefenoxam + chlorothalonil, azoxy-strobin, mancozeb, and maneb), and lepidopterous larvae and silverleaf whitefly (Bacillus thuringiensis, endosulfan, bifentrin, potassium salts of fatty acids, and spinosad).

Watermelons were harvested twice during the 15-22 May and 3 –9 June periods. Marketable fruit (U.S. No. 1 or better) according to the U.S. Standards for Grades of Watermelons (U.S. Dept. Agr., 1978) were separated from culls and counted and weighed individually. Fruit 12 lbs and larger were assumed to be marketable. Soluble solids (a measure of sweetness) determinations were made with a digital, hand-held refractometer on eight fruit of each entry at the first harvest, polar and equatorial dimensions were obtained and the incidence of hollowheart was recorded for these fruits. Flesh color was visually estimated. Data were subjected to analysis of variance and mean separation was by Duncan=s multiple range test.

 

Results and Discussion

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

Early yields ranged from 238 cwt/acre for RWM 8151 to 518 cwt/acre for ‘Summer Flavor 790’. Fifteen other entries had early yields similar to those of ‘Summer Flavor 790’. Average early harvest fruit weight varied from 18.7 lbs for ZG 8902 to 28.8 lbs for ‘Dulce’. Soluble solids for the early harvest fruit ranged from 11.6% for ‘Celebration’ to 13.6% for HSR 2965. Soluble solids for all entries exceeded the 10% specified of optional use to designate very good internal quality in the U.S. Standards for Grades of Watermelons (U.S. Dept. Agr., 1978). The incidence of hollowheart in those fruit sampled varied from 0% in six entries (HSR 2965, ‘Jamboree’, ‘Summer Flavor 790’, ‘Mardi Gras’, HSR 2955, and 98212) to 100% in ‘Dulce’. Hollowheart was especially severe in ‘Dulce’, RWM 8151, HSR 3028, ZG 8901, and ‘Gold Strike’.

Total yields (Table 2) varied from 424 cwt/acre for ‘Delta’ and 98212 to 729 cwt/acre for ‘Montreal’. Twenty-one other entries had yields similar to those of ‘Montreal’. Average fruit weight over the entire season ranged from 18.5 lbs for ‘Fiesta’ to 25.4 lbs for ‘Dulce’. Fruit per plant varied from 1.5 for ‘Delta’, WX 264, and 98212 to 2.4 for HSR 2965. Cull fruit ranged from 2% by weight for SSC 46104 to 20% for WX 264.

The proportion of fruit in market weight classes is shown in Table 3. ‘Delta’, HSR 3028, ‘Sentinel’, and ‘Summer Flavor 790’ produced 50% or more of their fruit in the most desirable 18-24 lb weight class. At least 80% of the fruit produced by ‘Dulce’, RWM 8151, and ‘Sentinel’ exceeded 18 lbs average weight.

 

Summary

Watermelon variety evaluations have been conducted at this location each spring season since 1991. The highest yields of individual varieties ranged from 439 cwt/acre in 1996 to 1026 cwt/acre in 1993. In spring 2003, the highest yield was 729 cwt/ acre which was somewhat less than the 12-year average yield of 773 cwt/acre.

Variety shape and rind patterns, based on observations in this trial, are shown in Table 1. Varieties producing blocky or elongated/blocky fruit are generally favored in the market. Distinctively 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 or medium green rind. Flesh color was generally good ranging from 3.3 for ‘Dulce’ to 4.8 for HSR 2942, Olé, RWM 8134, and ‘Sangria’.

Based on this and previous trials, the following ‘Allsweet’ and blocky ‘Crimson Sweet’ type varieties are expected to perform well in Florida: ‘Daytona’, ‘Jamboree’, ‘Mardi Gras’, ‘Montreal’, ‘Regency’, ‘Sangria’, ‘Sentinel’, ‘Stars-N-Stripes’, and Summer Flavor 790, 800, and 900 series. Other varieties may perform equally well on some farms.

 

Note

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

 

Acknowledgment

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

 

Literature Cited

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

Hanlon, E. A. and J. M. DeVore. 1989. IFAS extension soil testing laboratory chemical procedures and training manual. Fla. Coop. Ext. Circ. 812.

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