Combining ability in relation to heterosis for quantitative characters in sugarcane

Genetic variances were estimated by full-sib and half-sib analysis in sugarcane among the 30 F₁s involving 10 female lines and 3 testers. Variances due to lines were significant for stalk height, stalk girth, and stalk weight, whereas variance due to testers was significant only for stalk density. Variances due lines x testers were significant for stalk height and stalk girth. σ²A/σ²D showed the predominant role of nonadditive gene action in the inheritance of No. of millable canes/stool, stalk height, stalk girth and stalk density, and additive gene action for stalk weightand stool weight. The degree of dominance wasin the range of overdominance for No. of millable canes/stool, stalk height, stalk girth and stalk density. Lines contributed maximum to variances due to hybrids for all the charactersexcept stalk density. On the basis of per se performance and gca effects, CoS 8210, Sea 271/78 and CoS 7931 were good general combiners for stool weight. On the basis of per se performance and sca effects and heterotic response, the crosses Sh 670/79 x Sca 4/79, P11598 x Sca 4/79, Sca 271/78 x CoS 7931 and UP1 x CoS 758 were best specific combinations for stool weight.