Heterosis and Combining Aability Aanalysis for Yield and Related-Yield Traits in Hybrid Rice

Study of combining ability and heterosis were conducted on 12 F1 hybrids along with seven rice genotypes (three cytoplasmic male sterile lines and four restorer varieties) to know the pattern of inheritance of some morphological traits for selecting superior genotypes. The experiment was carried out according to line x tester mating design, in Sari Agricultural Sciences and Natural Resources University (SANRU) agricultural experiment station, during 2007-08. Analysis of variance revealed significant differences among genotypes, crosses, lines, testers and line x tester interactions for tiller number, plant height, days to 50% flowering, panicle length, number of spikelets per panicle, spikelet fertility and grain yield traits. Variances of SCA were higher than the GCA variances for traits except for plant height which indicated predominance of non-additive gene action nature of inheritance of the traits. The highest heterosis (106.60%) was observed in cross IR68899A x Poya followed by other eight crosses for yield and most of its related traits. The proportional contribution of testers was observed to be higher than that of the interactions of line x tester that revealed the higher estimates of GCA variance that shwon an additive gene action existing among the testers used. Within CMS parents, IR62829A and among male parents, IR50 and Poya were observed to be good general combiners for most of the characters studied. The cross combinations IR62829A x Mosa-tarom, IR68899AxPoya, IR58025AxIR50 and IR58025AxPoya were observed to be good specific cross combinations for grain yield and most of its related traits due to highly significant SCA and heterotic effects.