Interaction of Flesh Color Genes in Watermelon

Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] flesh color is controlled by several genes to produce red, orange, salmon yellow, canary yellow, or white. The objective of these experiments was to study the interaction of three independently reported gene loci, each having two or three alleles: C (canary yellow) versus c (red), y (salmon yellow) versus Y (red) versus y8 (orange), and i (inhibitory to C) versus I (noninhibitory to C). The interaction of C, y, y8, and i is of interest to those developing new cultivars of watermelon and has not been reported previously. Five crosses were used to study gene action: Yellow Baby 3 Tendersweet Orange Flesh, Yellow Doll 3 Tendersweet Orange Flesh, Yellow Baby 3 Golden Honey, Yellow Doll 3 Golden Honey, and Yellow Baby 3 Sweet Princess. Based on performance of PA, PB, F1, F2, BC1A, and BC1B, the parents have the following genotypes: Yellow Baby 5 CCYYII, Yellow Doll 5 CCYYII, Tendersweet Orange Flesh 5 ccy8y8II, Golden Honey 5 ccyyII, and Sweet Princess 5 ccYYii. Segregation of flesh color in the progeny of the five families supported the previous report of a multiple allelic series at the y locus, where Y (red) was dominant to y8 (orange) and y (salmon yellow). In conclusion, epistasis is involved in the genes for major flesh colors in watermelon, with ii inhibitory to CC (canary yellow), resulting in red flesh, and CC (in the absence of ii) epistatic to YY, producing canary flesh.