Quantitative Analysis of Generations for Inheritance of Fruit Yield in Watermelon

There is a large genetic diversity for fruit size and yield in watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus]. Current cultivars have high fruit quality but may not be the highest yielders. This study was designed to estimate variance components and heritability of fruit yield (Mg.ha(-1)), fruit count (th.ha(-1)), and fruit size (kg/fruit) in a cross involving high-yielding 'Mountain Hoosier' with low-yielding 'Minilee'. Six generations (PaS1, PbS1, F-1, F-2, BC1Pa, and BC1Pb) were developed and tested in Summer 2008 at two locations in North Carolina. Discrete classes were not observed within the F-2 segregating population. The actual distribution of the F-2 population for fruit yield, fruit count, and fruit size deviated from the normal distribution. 'Mountain Hoosier' had higher parental and backcross variance than 'Minilee'. High F-2 variance for fruit yield indicated large phenotypic variance. There was a larger environmental variance than genetic variance associated with the yield traits. Estimates of broad- and narrow-sense heritability were low to medium. A large number of effective factors indicated polygenic inheritance for fruit yield and fruit size. Gain from selection for yield is amendable by selection. As a result of this complex inheritance, selection based on individual plant selection in pedigree method may not be useful for yield improvement in this population. Hence, a selection scheme based on progeny testing using replicated plots, perhaps at multiple locations, is recommended.