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Triploid (seedless) watermelon [Citrullus lanatus (Thunb.) Matsum. and Nak.] pollen is nonviable; thus, diploid (pollenizer) watermelon cultigens are required to supply viable pollen for triploid watermelon fruit set. The objective of this research was to characterize maximum potential vegetative growth, staminate and pistillate flower production over time, and measure exterior and interior fruit characteristics of pollenizer cultigens. Sixteen commercially available and numbered line (hereafter collectively referred to as cultigens) pollenizer and two triploid cultigens were evaluated in 2005 and 2006 at Clayton, NC. Vegetative growth was measured using vine and internode length, and staminate and pistillate flower development was counted weekly. Fruit quality and quantity were determined by measuring individual fruit weights, soluble solids, and rind thickness. Based on vegetative growth, pollenizer cultigens were placed into two distinct groups. Pollenizers, which produced a compact or dwarf plant were ‘Companion’, ‘Sidekick’, ‘TP91’, ‘TPS92’, and ‘WC5108-1216’. Pollenizers having a standard vine length were ‘Jenny’, ‘High Set 11’, ‘Mickylee’, ‘Minipol’, ‘Pinnacle’, ‘Summer Flavor 800’ (‘SF800’), ‘Super Pollenizer 1’ (‘SP1’), and ‘WH6818’. Cultigens with compact growth habit had shorter internodes and vine lengths compared with the cultigens with standard growth habit. Cultigens with the greatest quantity of staminate flower production through the entire season were ‘Sidekick’ and ‘SP1’. The lowest number of staminate flowers was produced by ‘TP91’ and ‘TPS92’. Based on fruit quality characteristics and production, pollenizers currently or possibly marketed for consumption include ‘Mickylee’, ‘SF800’, ‘Minipol’, ‘Jenny’, and ‘Pinnacle’. The remaining cultigens evaluated in this study should be used strictly as pollenizers based on fruit quality. Arrangement of diploid pollenizers in a commercial planting of triploid watermelons is an important consideration depending on plant vegetative development. Based on staminate flower production, cultigens with higher staminate flower production are potentially superior pollenizers and may lead to improved triploid quality and production. Furthermore, pollenizer selection by fruit characteristics should include a rind pattern easily distinguished from triploid fruit in the field. Watermelon production in the United States was 38 million pounds in 2005 [U.S. Department of Agriculture (USDA), National Agricultural Statistics Service, 2006]. Triploid (seedless) watermelons were introduced to the United States in 1951 (Kihara, 1951); and in 2005, three-fourths of the United States’ watermelon production was devoted to triploid cultivars (USDA, Economic Research Service, 2005). In triploid watermelon production, diploids are included as a viable pollen source for pollination and fruit set (Kihara, 1951; Rubatzky and Yamaguchi, 1997). To provide sufficient pollen for maximum triploid fruit yield, plants should be planted in a ratio of one pollenizer plant for every two to four triploid plants (Fiacchino and Walters, 2003; Maynard and Elmstrom, 1992; NeSmith and Duval, 2001). The pollenizer cultivar has an effect on the yield of triploid fruit (Fiacchino and Walters, 2003; Freeman et al., 2007b). Triploid plants and pollenizers can be planted in separate rows or interplanted in the same row (Maynard and Elmstrom, 1992). The separate row planting method establishes one row of pollenizers and then two to four rows of triploids (Maynard and Elmstrom, 1992; Rubatzky and Yamaguchi, 1997). NeSmith and Duval (2001) reported a decrease in yield when the pollenizer ‘Ferarri’ was planted more than 6 m from the triploid ‘Genesis’ indicating that field arrangement of the pollenizer is an important consideration. Planting a pollenizer in the same row to reduce the distance between pollenizer and triploid plant can be done by planting the pollenizer in between two to three triploid plants (interplanted) or by planting a pollenizer in every third or fourth hill that would normally be occupied by a triploid plant. Planting in the same row adds complexity to the planting and harvesting of the crop (Maynard and Elmstrom, 1992). Pollenizer fruit should have a different rind pattern from the triploid so it can be separated and marketed properly (Kihara, 1951; Maynard and Elmstrom, 1992). The objective of this research was to characterize and quantify the growth and development of diploid watermelon pollenizers, especially recently bred pollenizers developed exclusively for triploid watermelon production (dedicated pollenizers). The vine and internode length were measured because plant competition and suitability of different planting arrangement for pollenizers need to be considered when planted with triploid plants. Determining number of flowers gives an understanding of potential pollen produced from the various pollenizers for fruit set on triploid watermelons. Counting fruit, quantifying harvestable fruit and size, measuring fruit qualities, and observing rind pattern provides information as to which pollenizers could be sold as seeded fruit as well as these that are more suitable for production with specific triploid cultivars. Materials and Methods Treatments. Thirteen pollenizer cultigens were evaluated: ‘Companion’, ‘Jenny’, ‘High Set 11’, ‘Mickylee’, ‘Minipol’, ‘Pinnacle’, ‘Summer Flavor 800’ (‘SF800’), ‘Super Pollenizer 1’ (‘SP1’), ‘Sidekick’, ‘TP91’, ‘TPS92’, ‘WC5108-1216’, and ‘WH6818’. Triploid watermelon cultigens, ‘Petite Perfection’ and ‘Tri-X-313’, were included for comparison of vegetative and floral habit. Cultural practices. Seeds were sown into 3.8 cm · 3.8-cm cell trays on 20 Apr. each year. Plants were grown in the greenhouse for 2 weeks and moved to a coldframe for 2 weeks of conditioning for field establishment. Seedlings were hand planted into beds covered with black polyethylene mulch at the Central Crops Research Station, Clayton, NC, into a Norfolk loamy sand (fine-loamy, kaolinitic, thermic typic Kandiudults) soil on 24 May 2005 and 17 May 2006. As beds were formed and just before mulch was laid, the soil was fumigated with 1,3-dichloropropene and chloropicrin (Telone C-35: Dow AgroSciences, Calgary, Alberta, Canada) and broadcast-fertilized (0N–0P–50K at 149.1 kg ha and 16N–0P–0K at 213.0 kg ha) according to soil test recommendations. Inrow spacing was 1.3 m and between-row spacing was 3.1 m. Plant spacing around plants was maximized to facilitate individual plant measurements. Four watermelon plants of each cultigen were included in each plot. Cultigens were arranged in a randomized complete block design with five replications. Pesticides and fertigation were applied based on North Carolina cultural recommendations (Sanders, 2004, 2005). Received for publication 8 July 2008. Accepted for publication 1 Nov. 2008. Technical assistance by W. Bradfred Thompson and statistical assistance from Joy Smith are greatly appreciated. Graduate research assistant. Professor. To whom reprint requests should be addressed; e-mail jonathan_schultheis@ncsu.edu. HORTSCIENCE VOL. 44(1) FEBRUARY 2009 59 JOBNAME: horts 44#1 2009 PAGE: 1 OUTPUT: December 29 22:41:23 2008 tsp/horts/180127/03114

Maximum Potential Vegetative and Floral Production and Fruit Characteristics of Watermelon Pollenizers