Study on parents combining ability and Gene action of some agronomic and Physiological traits in rapeseed hybrids (Brassica napus L.)

In order to estimate combining ability, heterosis and gene action, 9 rapeseed lines were selected and crossed in 9×9 half diallel method in research field of Dryland Agricultural Research sub-Institute (Kermanshah) in 2008. The parents and their 36 crosses evaluated in an RCBD with 3 replications for 8 agronomic and physiologic traits in 2009. Results showed significant differences among genotypes mean squares of all traits. Specific combining ability variance for all traits except 1000 seeds weight was significant. General combining ability variance for all traits except plant height was significant. The results of genetic variance components and heritability showed that plant height, number of seeds per pod, number of pods per plant, relative water content and seed yield were controlled by dominant genes and had low narrow sense heritability. In contrast, ion leakage was controlled by additive genes and had high narrow sense heritability. 1000 seeds weight was controlled by additive and dominant genes and had moderate narrow sense heritability. Estimation of heterosis in hybrids showed that it was positive and significant in some traits like number of pods per plant and seed yield, in spite of weak and non-significant GCA of parents. It was due to high proportion of dominant variance in heritability of these traits. On the bases of results IL4× IL9 cross due to positive and significant GCA of its parents for seed yield and negative GCA for ion leakage might be used in breeding programs to access high productive rapeseed genotypes. Three hetrotic crosses, i.e. IL1× IL8, IL6× IL9 and IL6× IL7 due to positive and significant SCA for seed yield can be used as thehighestyielding single cross hybrids of rapeseed for introducingto farmers.