Variance Component Analysis of Sex Expression-Related Traits In Melon (Cucumis melo L.)

Understanding sex expression is important for hybrid seed production. Sex expression in melon is influenced by both genetic and environmental factors as well as their interactions, which however are not well studied. In the present study, in two-year (2007 and 2008) trials, we investigated the inheritance of flowering-related traits in melon with variance component analysis in three populations (F₁, F₂ and F₃) derived from a cross between two inbred lines 3-2-2 (monoecious) and Top Mark (andromonoecious). Traits under investigation included days to the first female flower (DFF), node to the first female flower (NFF), and the percentage of female flowers (PFF). Only NFF in F₂ generation was significant; all traits of F₃ progeny except the NFF in 2008 were significant indicating that flowering-related traits were moderately affected by environment condition. DFF was shorter in spring of 2008 than that in fall of 2007. PFF in spring of 2008 was higher than the parental lines in fall of 2007. However, the performance of F₁, F₂, and F₃ progeny in spring of 2008 was lower than that in the fall of 2007 for NFF. No difference was found in all three traits in F₁ in both seasons. However, the difference of F₁ and F₃ progeny from parental lines in two seasons estimated with regard to the time of the appearance of the first female flower. Dfference was found between the relative contribution of additive and dominance genetic variances across growing environments in flower related traits. The contribution of the additive genetic variances to the total genetic variances in the fall of 2007 was 0.18, 0.06, and 0.36 in fall 2007, and 1.20, 0.01 and 0.01 in spring, 2008 for DFF, NFF, and PFF, respectively indicating that additive gene effects may be important. While the respective narrow sense heritability for DFF, NFF and PFF in spring of 2008 was 43, 3 and 19 %, the broad sense heritability of DFF< NFF and PFF was 11.2, 53.6 and 29.4%, respectively.