Determination of Gene Effects and Combining Ability of Early Maturity and Yield Triats In Rice

Five rice genotypes (Hassani, Dailamani, Shastak-mohammadi, Sange-tarom andDaei-shastak) and their 10 hybrids obtained through half a diallel set were evaluated forcombining ability and gene effects studies of early maturity and yield traits. Singleseedlings of each entries were transplanted at 20×20 cm spacing in 2×4 m2 plots using arandomized block design with three replications during 2004-2005 at research station ofSari Agricultural Sciences and Natural Resources University. General combining ability(GCA) and specific combining ability (SCA) were calculated for these agronomic traits.The results showed significant difference between general (GCA) and specificcombining ability (SCA) for the investigated characters. This indicates the role ofadditive and non-additive gene effects in inheritance of the traits. Also the resultsshowed that selection for early maturity and yield characters can’t well succeed,because of there were a high amount of non-additive gene effects in the geneticvariance. Thus, these characters were important for production of hybrid variety andapplication of heterosis. In this study, investigation of graphic Wr-Vr analysis for earlymaturity indicated overdominance effect because the regression line intercepted the Wraxis at negative point (a = -6.64). The GCA effects of each parent for these traitsshowed that the Daei-shastak is good general combiner for yield.