Combining ability analysis of rapeseed genotypes under restricted nitrogen application.

Half diallel crosses of rapeseed (Brassica napus L.) varieties along with their parents were evaluated for siliquae per main shoot, siliquae per plant, seeds per siliqua, 1000-seed weight and seed yield without application of nitrogen. Analysis of variance based on Griffing’s method revealed significant mean squares of general combining ability (GCA) and specific combining ability (SCA) for all the traits. Significant ratio of GCA to SCA mean square and high narrow-sense heritability estimate observed for 1000-seed weight indicated the prime importance of additive genetic effects for controlling this trait. Significant positive correlation was exhibited between the GCA effects of siliquae per main shoot and seed yield, but for SCA effects, siliquae per plant had important role for seed yield. The parent PF7045/91 having significant positive GCA effects for yield components along with seed yield may be considered as good combiner. However, most of the crosses with significant positive SCA effects for seed yield had at least one parent with significant positive GCA effect for yield components.