A set of diallel crosses involving nine genotypes of rice (Oryza sativa L.) with early and medium maturity were evaluated for grain yield, morpho–physiological and some of the quality traits. Gene action estimated through Harman’s (1954) approach revealed that both additive and non additive gene actions for traits viz., plant height(cm), days to 50% flowering, leaf area index(%), harvest index(%), net-assimilation rate(g cm-² day-¹), biological yield(g), grain yield(g), panicle length(cm), 100 grain weight(g), grain length(mm), grain breadth(mm), dry matter(g) and L\B ratio. Non-additive gene action (dominance and epistasis) were predominant as compared to additive gene action except for L\B ratio, which is easily transferred through hybridization for crop improvement programme. The positive and negative genes in the parents were distributed unequally for all the traits except for harvest index (0.25). Correlation coefficient was negative and significant indicating the dominance of positive genes for days to 50% flowering, grain yield per plant, days to maturity and 100 grain weight. Significant value of F for days to 50% flowering, days to maturity, leaf area index and grain breadth indicated asymmetrical distribution of dominant and recessive genes in the parents. The high heritability in narrow sense was established for days to 50% flowering, days to maturity leaf area index and medium for plant height, length of panicle, 100 grain weight and net-assimilation rate. Consequently any selection method adopted could lead to desirable improvement in the above mentioned traits. For varietal

improvement in very early group, the exploitation of parent VLDhan 221 might be useful, as it possesses more number of desirable recessive genes for earliness.