Estimation of C o mbining Ability and Gene Effects of Grain Density at Rice (Oryza Sativa L.)

Five rice genotypes (Hasseni, Dailamani, Shastak-mohammadi, Sange-tarom andDaei-shastak) and their 10 hybrids obtained through half diallel set were evaluated forcombining ability and gene effect studies of grain density trait. Single seedlings of eachentries were transplanted at 20×20 cm spacing in 3×5 m2 plots in a randomized blockdesign replicated three times during 2004-2005 at research station of Agricultural Sciencesand Natural Resources University General combining ability (GCA) and specific combiningability (SCA) was analyzed for this agronomic trait. The results showed significantdifference between general (GCA) and specific combining ability (SCA) for theinvestigated character. This indicates the role of additive and non-additive gene actionin inheritance of the trait. Also the results showed that selection for grain densitycharacter can’t well succeed, because of there was a high amount of non-additive geneaction in the genetic variance. Thus this character was important for production ofhybrid variety and application of heterosis. In this study, investigation of graphic Wr-Vranalysis for grain density indicated overdominance effect because the regression lineintercepted the Wr axis at negative point (a = -118/024). Also, the GCA effects of eachparent for this trait showed that the Daei-shastak is good general combiner for graindensity.