Effect of Cultivar, Polyploidy and “Reciprocal” Hybridization on Characters Important in Breeding Triploid Seedless Watermelon Hybrids1

Abstract

Abstract C5 (sister line of ‘Sweet Princess’), ‘Sugar Baby’ and ‘Florida Giant’ cultivars of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai], and their hybrids were compared at the diploid (2x), triploid (3x) and tetraploid (4x) chromosome levels. Ovary, fruit and seed shape was significantly rounder in the polyploids than in the diploids. There was no change in fruit shape in the already round cultivar, ‘Sugar Baby’. Fruit weight and ploidy level were inversely related. Hollow heart was more severe in the polyploids. The polyploids had a significantly thicker rind, contained larger seed, and were more field resistant to anthracnose than were the diploids. “Reciprocal” triploid hybrids [C5 (4x) x ‘Sugar Baby’ (2x) compared to ‘Sugar Baby’ (4x) x C5 (2x)] had significantly different means for ovary shape, fruit shape and anthracnose resistance. The “reciprocal” triploid hybrids differed significantly in 1 of 2 seasons for the traits fruit weight, hollow heart incidence, rind thickness, and seed shape. In breeding seedless watermelon hybrids it is important to consider the parent cultivar used as the seed (tetraploid) parent.