HORTSCIENCE 43(1):274–275. 2008. ever, all cultivars examined had high average viability and probably had no effect on reproductive success (Brevis et al., 2006). Pollen Viability of Selected Diploid Cultivars used in this study were chosen because previous research has illustrated Watermelon Pollenizer Cultivars differences in their performance and pollen 1 viability may be a contributing factor (Freeman Josh H. Freeman et al., 2007). The objective of this research Department of Horticulture, Virginia Polytechnic Institute and State was to determine the pollen viability of four University, Eastern Shore Agricultural Research and Extension Center, diploid watermelon pollenizer cultivars. Painter, VA 23420 Materials and Methods Stephen M. Olson Department of Horticultural Sciences, University of Florida, North Florida On 3 Apr. and 1 Aug. 2006, 4-week-old Research and Education Center, 155 Research Road, Quincy, FL 32351 watermelon seedlings were transplanted into raised beds covered with black polyethylene Eileen A. Kabelka mulch in the spring and white on black Department of Horticultural Sciences, University of Florida, Box 110690 polyethylene mulch in the fall. Experiments were performed at the North Florida Re- Fifield Hall, Gainesville, FL 32611 search and Education Center (NFREC) in Additional index words. Citrullus lanatus, Cucurbitaceae, seedless, in-row pollenizer, triploid, Quincy, FL. Soil type at NFREC is Norfolk special pollenizer loamy sand (fine-loamy, kaolinitic, thermic Typic Kandiudults). The experimental design Abstract. In the Spring and Fall 2006, the pollen viability of four diploid watermelon was a randomized complete block with four pollenizers was evaluated in Quincy, FL. Triploid watermelon plants [Citrullus lanatus replications. The pollen viability of four (Thunb.) Matsum. & Nakai.] do not produce sufficient viable pollen to pollenize diploid pollenizer cultivars, ‘Companion’, themselves and a diploid cultivar must be interplanted as a pollen source. Recent studies ‘Jenny’, ‘Mickylee’, and ‘SP-1’, was deter- have illustrated differences in triploid watermelon yields as a result of the pollenizer mined. Experimental plots were 4.57 m long cultivar used. The viability of the pollen produced by pollenizer cultivars may greatly with in-row spacing of 0.91 m and between- influence the fruit set and fruit quality in the triploid watermelon crop. Pollen samples row spacing of 2.43 m. Three pollenizer were taken from ‘Companion’, ‘Jenny’, ‘Mickylee’, and ‘SP-1’ and were stained to seedlings were planted at even spacing in determine their viability. There were no significant differences in pollen viability among the center of each plot. Fertilization, irriga- cultivars and all cultivars had high average viability. Pollen viability was never lower tion, and pesticide application practices were than 95% for any cultivar. This study indicates that pollen viability of the cultivars followed using recommendations provided evaluated should not influence their effectiveness as pollenizers. by the University of Florida Institute of Food and Agricultural Sciences (Olson et al., 2006). Seedless watermelons account for 78% and Schultheis (2005) illustrated that there In the spring, sampling was initiated on 17 of the watermelons sold in the United States were no statistical differences in pollen pro- May with additional pollen samples taken on (U.S. Department of Agriculture, 2006). duction between the two cultivars. This 24 May and 31 May. For the fall, sampling Triploid watermelon plants do not pro- suggests that there may be other factors that was initiated on 31 Aug. with other pollen duce sufficient viable pollen to pollenize contribute to a pollenizer’s performance. samples taken on 7 Sept. and 14 Sept. The themselves and a diploid cultivar must be Pollen viability could be a determining sampling period was scheduled to coincide interplanted as a pollenizer (pollen source) factor in the performance of watermelon with the fruit-setting period of adjacent trip- (Maynard and Elmstrom, 1992). Growers pollenizers. Pollen flow from a pollenizer loid plants transplanted on the same date. have traditionally planted every fourth or would be of little value if the viability was On the sampling dates, watermelon flow- fifth row in the field with a diploid cultivar low, because pollen tube growth and ovule ers were removed from the plant before the and harvested both seeded and seedless fertilization are necessary for seedless fruit flowers opened. This was to ensure that watermelons. maturation (Maynard and Elmstrom, 1992; pollinators would not remove pollen and an Diploid cultivars have recently been Rhodes et al., 1997; Robinson and Decker- adequate supply of pollen would be available developed to be planted in-row as pollen Walters, 1997). Poor pollination in water- for analysis. Three staminate flowers were sources between triploid plants without alter- melon can affect fruit shape and thus its removed from each plot and placed into ing the triploid spacing’s or affecting market- marketability and may be a contributing plastic cups and covered to exclude pollina- able yield. Freeman et al. (2007) observed factor to the physiological disorder termed tors. Flowers were taken to the laboratory and significant differences in the performance hollowheart (Fiacchino and Walters, 2003; of in-row pollenizers based on seedless Maynard, 1992). Research in other plant watermelon yield. Triploid plants pollenized families has shown that there can be sub- Table 1. Analysis of variance for pollen viability by ‘Companion’ yielded less than those stantial differences in pollen viability within a of watermelon pollenizer cultivars tested in pollenized by ‘Jenny’, ‘Patron’, ‘SP-1’, and species and between closely related species Spring and Fall 2006 at Quincy, FL. ‘Sidekick’. Fiacchino and Walters (2003) (Fortescue and Turner, 2004; Lavi et al., Source df MS P value demonstrated that ‘Crimson Sweet’ was a 1996; Nikkanen et al., 2000; Parzies et al., Spring more effective pollenizer than ‘Fiesta’ based 2005). Fortescue and Turner (2004) reported Replication 3 0.00410 0.410 on greater seedless watermelon yields and significant differences in pollen viability Sampling date 2 0.02827 0.003 Cultivar 3 0.00856 0.124 less incidence of hollowheart. Studies on between cultivars of banana (Musa acumi- Date*cultivar 6 0.00281 0.669 ‘Crimson Sweet’ and ‘Fiesta’ by Stanghellini nata Colla). Studies conducted in mandarin Error 33 0.00415 orange (Citrus reticulata Blanco) have Fall shown that pollen source can affect yield Replication 3 0.00290 0.408 Received for publication 11 July 2007. Accepted and quality characteristics such as soluble Sampling date 2 0.00302 0.367 for publication 7 Aug. 2007. solids (Vithanage, 1991; Wallace and Lee, Cultivar 3 0.00281 0.422 1To whom reprint requests should be addressed; 1999). Differences in pollen viability have Date*cultivar 6 0.00257 0.519 e-mail [email protected] been reported in rabbiteye blueberry; how- Error 33 0.00292
274 HORTSCIENCE VOL. 43(1) FEBRUARY 2008 Table 2. Pollen viability of four diploid watermelon pollenizer cultivars at Quincy, FL, during the Spring of pollen and pollen-ovule ratios in four rabbi- and Fall 2006. teye blueberry cultivars. J. Amer. Soc. Hort. Pollen viability Sci. 131:181–184. Dafni, A., M. Neppi, and E. Pacini. 2005. Pollen Pollenizer cultivar 17 May 24 May 31 May 31 Aug. 7 Sept. 14 Sept. and stigma biology, p. 83–147. In: A. Dafni, P.G. z z z z z z Mickylee 97.8 NS 98.0 NS 98.7 NS 97.4 NS 98.2 NS 97.8 NS Kevan, and B. Husband (eds.). Practical pollina- Companion 97.4 97.2 99.2 97.6 98.1 98.8 tion biology. Enviroquest, Cambridge, Canada. Jenny 97.3 97.2 98.3 97.8 97.7 97.0 Fiacchino, D.C. and S.A. Walters. 2003. Influence SP-1 97.2 95.5 98.1 97.9 98.7 97.6 y y of diploid pollenizer frequencies on triploid Date means 97.4 b 97.0 b 98.6 a 97.7 NS 98.2 97.8 watermelon quality and yields. HortTechnol- zP = 0.05; means are compared within the same column. ogy 13:58–61. yP = 0.05; means from the same season are compared within the row. Fortescue, J.A. and D.W. Turner. 2004. Pollen NSNonsignificant. fertility in Musa: Viability in cultivars grown in southern Australia. Australian J. Agr. Res. 55:1085–1091. Freeman, J.H., G.A. Miller, S.M. Olson, and W.M. allowed to open. Samples were analyzed after 24 May, respectively. The average pollen Stall. 2007. Diploid watermelon pollenizer anther dehiscence was verified using a hand viability over all cultivars and all dates for cultivars differ with respect to triploid water- lens. Pollen was removed from the anthers spring and fall were 97.7% and 97.9%, melon yield. HortTechnology 17:518–522. and placed on a slide. Viability was deter- respectively. There was little variation within Lavi, U., S. Nachman, I. Barucis, D. Gaash, and A. mined using the diaminobenzidine (DAB) the data and the coefficients of variation were Kadman. 1996. The effect of pollen donors and test for peroxidase activity in pollen (Dafni never higher than 0.84%. pollen viability on fruitlet drop in Macadamia et al., 2005). Rodriguez-Riano and Dafni integrifolia (Maiden & Betche). Trop. Agr. (2000) compared the results of four vital dyes 73:249–251. Discussion Maynard, D.N. 1992. Growing seedless water- versus pollen germination results and illus- melon. Univ. Fla. Coop. Ext. Serv. Fact sheet trated the superiority of peroxidase tests over The results of this study illustrate that HS687. 10 Dec. 2006.
HORTSCIENCE VOL. 43(1) FEBRUARY 2008 275