Estimation of combining ability for yield and yield components in rice (Oryza sativa L.) cultivars using diallel cross

In order to estimate combining ability and gene action of a number of rice cultivars, a 5 x 5 half a diallel cross genetic design has been used. Parents and their hybrids have been evaluated in a randomized complete block design with 3 replicates for yield and 6 yield components in 2007 in Rice Research Station of Iran-Amol. Mean squares of genotypes for all traits were highly significant (p < 0.01). Significant mean squares of combining ability for all traits showed additive and non-additive effects in control of the related traits. Having nonsignificant MS(GCA)/MS(SCA) ratio for all traits but 1000-grain weight show higher importance of nonadditive effects in comparison with additive effects of controlling genes. High relative importance of specific combining ability indicated that all traits but 1000-grain weight are highly affected by impacts of specific combining ability. Generally, Dasht, Neda and Binam were the best parents for general combining ability and Binam x IR62871-175-1-10 and Mashhad Domsiah x Binam were the best hybrids for grain yield and its components.