Genetic Analysis of Resistance to Races of Magnaporthe grisea the Causal Agent of Blast Disease in some Iranian Rice Cultivars

To study genetic architecture of resistance of rice to blast disease، five diverse rice cultivars viz. Neda، Dasht، Domsiah، SHZ-2 and Ahlami tarom were selected and all cross combinations were made among them (a half-diallel). All genotypes including ten F1 together with their five parents، were evaluated in RCBD with three replications for components of resistance to blast in Rice Research Institute of Iran in Rasht and Amol during 2005-2007. Analysis of variance showed that there were significant differences among all rice cultivars and their cross combinations for all traits. Combining ability analysis based on Method II and Model Mixed B (Griffing) revealed that mean of squares for GCA and SCA were significantly different، hence both additive and non-additive components of genetic variance were important in controlling of traits. For most of traits additive components were predominant. Cultivars Neda، Dasht and SHZ-2 were good combiner for increasing resistance to blast disease. Most of combinations showed high significant SCA for components of resistance. Genetic analysis through Hayman`s method also proved the results obtained via Griffing’s method.