Estimation of gene action and heritability of important agronomic traits in rice (Oryza sativa L.)

In order to estimate the gene action and heritability of 8 important agronomic traits, 6 genotypes of rice were studied in a 6×6 half-diallel cross. Parents and their progenies were grown in a randomized complete block design with three replications in Field Research Station of the University of Guilan, Rasht, Iran, in 2006 cropping season. Eight traits including pre-anthesis phase, post anthesis phase, flag leaf area, panicle length, number of grain per panicle, 1000 grain weight and grain yield were evaluated. Analysis of variance of data showed significant differences (p<0.01) between genotypes for all studied traits. Results from graphical analysis based on Hayman method showed that non-additive effect for all traits, except pre-anthesis phase and panicle length, were important than the additive effect. Pre-anthesis phase and panicle length were controlled by partial dominance effect (with higher additive effect) and the other traits were controlled by over-dominance gene effect in selected genotypes. For panicle length, the parents had more recessive allele frequencies, while for other traits the frequencies of dominant alleles were greater in parents. Narrow-sense heritability varied from 0.165 to 0.794 for duration of post-anthesis phase and panicle length, respectively. It can be concluded that both hybridization and selection approaches can be used to improve panicle length and duration of pre-anthesis phase, however, for the other traits including grain yield heterosis and hybrid development are recommended.