Discovery of second gene for solid dark green versus light green rind pattern in watermelon

The watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus) has high variability for fruit size, shape, rind pattern, and flesh color. This study was designed to measure the qualitative inheritance of rind phenotypes (solid dark green vs. light green). For each of the 2 families, "Mountain Hoosier" × "Minilee" and "Early Arizona" × "Minilee," 6 generations (P(a)S(1), P(b)S(1), F(1), F(2), BC(1)P(a), BC(1)P(b)) were developed. Each family was tested in summer 2008 in 3 environments in North Carolina. Phenotypic data were analyzed with the χ(2) method to test the segregation of Mendelian genes. Deviations from the expected segregation ratios based on hypothesized single dominant gene for solid dark green versus light green rind pattern were recorded, raising questions on the inheritance of this trait. Inheritance of solid dark green rind versus light (gray) rind showed duplicate dominant epistasis. Duplicate dominant epistasis gives rise to a 15:1 ratio (solid dark green:light rind pattern) in F(2) generation. When both the loci are homozygous recessive, we observe light rind pattern. The g-1 and g-2 genes were identified to control light green rind when in homozygous recessive form.