Genetic Divergence, Combining Ability and Heterosis for Yield andPaperback, 18 April 2012

The experiment was carried out with genetic divergence of spring wheat and combining ability, heterosis and heritability for yield and yield contributing characters from a five parent- half diallel cross in F2 generation for genotypes of wheat. Genetic divergence was assessed through Mahalanobis' D2 -statistics and Principal Component Analysis (PCA). The genotypes were grouped into six clusters. The combining ability analysis studied in the diallel cross populations. General combining ability (GCA) and specific combining ability (SCA) mean squares in F2 generation was significant for all the characters. There was significant expression of non additive gene actions even in F2 generation, which indicates that epistatic components of non additive gene actions might have been involved. The crosses Sonora x Opata and SA-92 x Rawal had positive and significant SCA effects for grain yield. Maximum mid parent heterosis for grain yield was 39.97% in the cross Sonora x NK-5 which was much higher than mid parent heterosis for other yield contributing characters. Positive relation was observed between heterosis of the crosses with their corresponding SCA effects.