Evaluation of Seedless Watermelon Varieties for Production in Southwest Indiana, 2010 Shubin K. Saha 1 and Daniel Egel 2 1 Vegetable Extension Specialist, Horticulture and Landscape Architecture Department, Purdue University, Southwest Purdue Agricultural Center, Vincennes, IN, 47591 2 Plant Pathologist, Botany and Plant Pathology Department, Purdue University, Southwest Purdue Agricultural Center, Vincennes, IN, 47591 Introduction Watermelon (Citrullis lanatus L.) production is one of the largest commercial horticultural crops in the state of Indiana with significant economic importance. In 2009, Indiana was ranked fifth in the U.S. in acres harvested (7,400) as well as total value (approximately $23.6 million) behind only Florida, Georgia, Texas, and California (USDA, 2010). To be successful, growers must consider many aspects of watermelon production. One of the primary aspects is the selection of an appropriate variety to meet the needs of the grower so the product can be successfully marketed. When selecting a variety, many traits are important including high yield, resistance to biotic diseases and disorders, good internal qualities (such as firmness and soluble solids content), and good external qualities. The objective of these experiments was to evaluate experimental or newly available varieties to assess adaptability to growing in the climate of southwestern Indiana including partial resistance to Fusarium wilt. Materials and Methods Field Experiment The experiment was established on April 20, 2010, when seeds of each variety were sown in 52- cell seedling flats for production of transplants in a greenhouse. A total of 30 different seedless watermelon varieties from various companies were transplanted in the field on May 14, 2010, with SP-5 as the pollinator. The experiment was conducted as a randomized complete block design with three replications. Experimental plots were 48 feet in length and 4 feet wide. Rows were spaced on 8-foot centers with 4-foot in-row spacing. There were 12 plants per plot in addition to six pollinators per plot. Plants were grown in a typical plasticulture vegetable system utilizing raised beds with black polyethylene mulch in combination with drip tape for irrigation when rainfall was insufficient. All fertilizer applications were pre-plant including 350 lbs. (46-0- 0), 100 lbs. (0-0-60), and 200 lbs. of pelletized lime per acre. Plants were harvested five times from July 21 to August 17, at which time each fruit was weighed. Additionally, nine fruits from each variety were evaluated for quality characteristics including percent soluble solids, size, rind thickness, and firmness. Yield data was analyzed by Fisher s least significant difference test using SAS statistical programs (SAS Institute, Cary, NC.) Greenhouse Experiment A greenhouse trial was conducted to evaluate 31 triploid watermelon varieties for resistance to race 1 of the Fusarium wilt pathogen, F. oxysporum f.sp. niveum. On September 16, watermelon was seeded six to a 1.67-liter pot containing a 4:1:1 mixture (v:v:v) of sand:peat:vermiculite. Approximately seven days later, emerged seedlings were thinned to three per pot. Each pot was an experimental unit and was replicated four times per variety in a completely randomized design. Four pots of Tri-X-313 were left uninoculated as a control. Fusarium oxysporum f. sp.
niveum race 1 (FON-1), originally collected from a triploid watermelon in Indiana and stored on sterile filter paper at 4 C, was regenerated on PDA. Four 1-cm disks from the leading edge of a FON colony were added aseptically to 100 ml of liquid mineral salts medium (Esposito and Fletcher, Arch. Biochem. Biophys. 93:369) and shaken at 150 rpm for 72 hours at room temperature. The predominately microconidial suspensions were filtered through cheesecloth and adjusted to 1 x 10 5 conidia/ml with the aid of a hemacytometer. On September 30, each pot received 150 ml of the inoculum solution poured onto the soil surface except for the Tri-X-313 controls. The Horsfall-Barratt rating system was used to evaluate severity of Fusarium wilt on watermelon seedlings on October 12, 14, 17, 19, and 21. The Area Under the Disease Progress Curve (AUDPC) was determined by trapezoidal integration. Results Troubadour was the variety with the highest numerical yield at 28.0 tons/acre and was significantly greater than nine of the 30 varieties evaluated (Table 1). The other 20 varieties did not differ from Troubadour in terms of yield, ranging from 19.3 tons/acre to 27.3 tons/acre. RWT8228 was the variety producing the greatest average melon weight at 19.1 lbs and was significantly greater than 25 of the varieties evaluated (Table 1). Troubadour also had the greatest number of fruit per acre and was significantly greater than 14 of the other varieties (Table 1). Fenway had the highest numerical percentage of soluble solids (12.4) and was significantly greater than 24 of the varieties evaluated (Table 2). However, the highest yielding variety, Troubadour, did not differ significantly from the sugar content of Fenway. The flesh of Distinction had the greatest numerical firmness (4.4 lbs-force) and was significantly greater than 22 of the varieties evaluated this season. Cronos had the greatest numerical rind thickness (0.87 inch) and was significantly greater than 27 of the varieties evaluated (Table 2). There were some significant differences with regard to degree of seedlessness, but all varieties were in the range of less than five seeds. One point to note different from past seasons is that yield data was affected to some extent. The reason for this was due to coyote feeding damage, thus unmarketable fruit were more prevalent in the 2010 season than in previous years. The unmarketable fruit were not included in the yield data. Symptoms of Fusarium wilt were first observed eight days post-inoculation. Fusarium wilt symptoms were observed in one pot of Tri-X-313 uninoculated controls, perhaps due to unintentional inoculation. Nine triploid varieties were not significantly different from AC 4674, the variety with the lowest AUDPC. Sixteen varieties had a significantly lower AUDPC than the variety with the highest AUDPC, Treasure Chest. Acknowledgements The authors would like to extend their appreciation to the following individuals for all their help and assistance with the completion of the variety trials this year: Bill Davis, Sara Hoke, Dennis Nowaskie, and Angie Thompson.
Table 1. Yields of various seedless watermelon varieties. Variety Seed Company Cwt/ Acre Tons/Acre Fruit No./Acre Avg. Fruit Weight (lbs) Troubadour HM 560.5 28.0 a 1 3,781.3 a 14.8 ghij AC4674 AC 546.1 27.3 ab 3,403.1 abc 16.2 cdefgh Melody SY 541.8 27.1 ab 3,592.2 ab 15.1 fghij Crunchy Red HM 537.7 26.9 ab 3,289.7 abcd 16.3 bcdefgh Cooperstown SM 537.2 26.9 ab 3,365.3 abc 15.9 defgh AC7167 AC 507.7 25.4 abc 3,025.0 abcde 16.7 bcdefgh AC6177 AC 504.9 25.2 abc 2,873.8 abcdef 17.9 abcd Palomar SY 493.5 24.7 abcd 2,873.8 abcdef 16.8 bcdef Tri-X 313 SY 492.3 24.6 abcd 2,911.6 abcdef 17.2 abcde Fresh Cut WI 490.9 24.5 abcd 3,025.0 abcde 16.1 defgh RWT8228 SY 472.9 23.6 abcde 2,457.8 bcdefg 19.1 a AC6277 AC 458.9 22.9 abcde 2,722.5 abcdefg 16.8 bcdef Imagination SY 446.8 22.3 abcdef 3,365.3 abc 13.3 ij Treasure Chest SD 442.5 22.1 abcdef 2,571.3 bcdefg 17.1 bcdef ACR4106 AC 441.4 22.1 abcdef 2,684.7 abcdefg 16.4 bcdefgh AC7197 AC 427.3 21.4 abcdefg 2,646.9 abcdefg 16.2 cdefgh WX4838 WI 423.9 21.2 abcdefg 2,873.7 abcdef 14.7 ghij Cut Master WI 418.7 20.9 abcdefg 2,798.1 abcdefg 15.2 efghi Fascination SY 416.9 20.8 abcdefg 2,571.2 bcdefg 16.4 bcdefgh Cronos SM 412.9 20.6 abcdefg 2,268.8 cdefg 18.1 abc Distinction SY 385.2 19.3 abcdefg 2,117.5 efg 18.3 ab Majestic SM 364.0 18.2 bcdefg 2,268.8 cdefg 15.9 defgh AC6127 AC 359.8 18.0 bcdefg 2,155.3 defg 16.6 bcdefgh Summer King SY 355.3 17.8 bcdefg 2,306.6 cdefg 15.3 efghi Fenway SM 328.1 16.4 cdefg 2,420.0 cdefg 13.5 ij AC7197 AC 311.2 15.6 defg 1,890.6 efg 16.7 bcdefg Triple Threat SY 307.6 15.4 defg 2,306.6 cdefg 13.1 j Indiana SW 288.0 14.4 efg 1,815.0 fg 15.5 efgh Sorbet HL 266.2 13.3 fg 2,041.9 efg 13.1 j Ruby HL 250.0 12.5 g 1,663.8 g 14.7 hij 1 Means in columns separated by Fisher s least significant difference test (P 0.05), means with same letter are not significantly different.
Table 2. Internal fruit quality of seedless watermelons. Variety Seed Company %SS 1 Firmness (lbs-force) 2 Fruit Length (in) Fruit Width (in) Rind Thickness (in) Degree of Seedlessness 3 Fenway Continued on next page SM 12.4 a 4 2.4 k 9.2 l 8.8 fghi 0.56 i 1.3 abc Indiana SW 12.4 a 2.6 hijk 9.7 kl 9.1 efghi 0.66 bcdefghi 1.3 abc Triple Threat SY 11.8 ab 2.7 ghijk 9.4 l 8.8 fghi 0.61 efghi 1.3 abc Sorbet HL 11.7 abc 3.1 efghij 9.3 l 9.1 cdefghi 0.67 bcdefghi 1.6 a WX4838 WI 11.6 abcd 2.8 ghijk 9.4 l 8.8 efghi 0.63 cdefghi 1.3 abc Troubadour HM 11.5 abcde 4.3 a 11.4 cdefg 9.0 efghi 0.72 bcdef 1.4 ab AC6277 AC 11.3 bcdef 3.3 efg 11.8 abcd 9.3 bcde 0.61 defghi 1.1 bc Cooperstown SM 11.2 bcdefg 3.0 fghijk 11.1 efghi 9.0 efghi 0.73 bcde 1.0 c AC7197 AC 11.2 bcdefg 4.0 abc 11.3 cdefgh 9.1 efghi 0.69 bcdefgh 1.3 abc Majestic SM 11.2 bcdefg 3.5 cdef 11.3 cdefgh 8.9 efghi 0.77 ab 1.3 abc Crunchy Red HM 11.1 bcdefgh 4.2 ab 12.1 ab 9.0 efghi 0.75 abc 1.3 abc Fresh Cut WI 11.0 bcdefghi 2.6 jk 11.6 abcdef 9.0 efghi 0.69 bcdefgh 1.3 abc Palomar SY 11.0 bcdefghi 2.8 ghijk 10.2 jk 9.7 abc 0.68 bcdefghi 1.3 abc AC7167 AC 11.0 bcdefghi 3.3 defg 11.2 defgh 9.0 efghi 0.57 hi 1.0 c Ruby HL 11.0 bcdefghi 2.6 jk 10.2 jk 8.6 i 0.65 bcdefghi 1.1 bc Tri-X 313 SY 10.9 bcdefghi 2.6 ijk 11.5 bcdefg 9.3 bcde 0.69 bcdefgh 1.1 bc Cut Master WI 10.9 bcdefghi 3.1 efghij 11.1 efghi 8.8 ghi 0.71 bcdefg 1.0 c AC6127 AC 10.8 defghi 3.1 efghij 10.9 ghi 8.6 i 0.59 ghi 1.1 bc RWT8228 SY 10.8 defghi 3.2 efgh 12.2 a 9.9 a 0.73 bcdef 1.3 abc Summer King SY 10.8 defghi 3.0 fghijk 11.6 abcdef 8.7 hi 0.65 bcdefghi 1.1 bc ACR4106 AC 10.7 defghi 3.2 efgh 11.7 abcde 9.3 bcdef 0.70 bcdefgh 1.0 c AC7197 AC 10.7 defghi 3.9 abcd 11.9 abc 9.2 cdefgh 0.69 bcdefgh 1.3 abc AC6177 AC 10.6 efghi 4.1 ab 10.9 ghi 9.8 ab 0.74 bcd 1.1 bc
Table 2 (continued) Variety Seed Company %SS 1 Firmness (lbs-force) 2 Fruit Length (in) Fruit Width (in) Rind Thickness (in) Degree of Seedlessness 3 Treasure Chest SD 10.6 efghi 2.9 ghijk 10.7 hij 9.9 a 0.60 fghi 1.1 bc Fascination SY 10.5 fghi 3.7 bcde 11.4 cdefg 9.3 bcdef 0.63 cdefghi 1.3 abc AC4674 AC 10.4 ghi 2.8 ghijk 11.3 cdefgh 8.6 i 0.71 bcdefg 1.4 ab Imagination SY 10.3 hi 3.1 efghij 9.9 kl 9.2 cdefg 0.63 cdefghi 1.1 bc Distinction SY 10.3 hi 4.4 a 10.5 ij 9.9 a 0.63 cdefghi 1.3 abc Cronos SM 10.2 i 4.1 ab 11.0 fghi 9.6 abcd 0.87 a 1.1 bc Melody SY 10.2 i 3.2 efghi 9.8 kl 9.1 defghi 0.65 bcdefghi 1.1 bc 1 %SS: percent soluble solids. Higher values are related to higher sugar content in the fruit. 2 Pressure: firmness of the flesh of the melon. Higher values are associated with higher firmness. 3 Degree of Seedlessness: 1=0 seeds, 2=1-5 seeds, 3=> 5 seeds. 4 Means in columns separated by Fisher s least significant difference test (P 0.05), means with same letter are not significantly different.
Table 3. Susceptibility to Fusarium wilt of various seedless watermelon varieties. Variety Seed Company AUDPC 1 Treasure Chest SD 303.5 a 2 Triple Threat SY 297.1 ab WX 4838 WI 288.8 ab Sorbet HL 271.2 abc Melody SM 262.6 abcd Cooperstown SM 251.4 abcd AC 7187 HQ AC 226.3 abcde Crunchy Red HM 224.8 abcde ACR 6277 AC 216.6 abcdef Tri-X-313 SY 212.1 abcdefg Ruby HL 207.2 abcdefg ACR 4106T AC 203.6 abcdefg Troubadour HM 196.1 abcdefg AC 7197 HQ AC 189.3 abcdefg Imagination SY 185.8 bcdefg Cut Master WI 169.1 cdefgh Fresh Cut WI 169.0 cdefgh ACR 6177 AC 153.6 defghi Fenway SM 127.7 efghij ACR 6127 AC 121.7 efghij Palomar SY 103.6 fghijk AC 7167 AC 98.4 ghijk Fascination SY 61.4 hijk Summer King SY 58.5 hijk Majestic SM 56.4 hijk Indiana SW 53.2 ijk Distinction SY 53.0 ijk Cronos SM 49.6 ijk RWT 8228 SY 30.5 jk Tri-X-313 control 3 SY 25.8 jk AC 4674 AC 6.3 k 1 Area Under the Disease Progress Curve. 2 Means within each column with a letter in common are not significantly different (Fisher s Protected LSD), P=0.05. 3 Uninoculated control
Literature Cited R. G. Esposito and A. M. Fletcher. 1961. Arch. Biochem. Biophys. 93:369. United States Department of Agriculture, 2010. National Agricultural Statistics Service. Vegetables 2009 Summary. http://usda.mannlib.cornell.edu/usda/current/vegesumm/vegesumm-01-27-2010.pdf.