Genetic parameters assessment of siliquae associated with stress indices in rapeseed cultivars

The objective of the present study was to determine the genetic control and heritability of siliquae per plant at two places including without and application of nitrogen (Pp and Ps) and its related stress tolerance indices based on half diallel crosses of six spring rapeseed varieties. Significant mean squares of general combining ability (GCA) were detected for Pp and Ps and also the other related stress indices except tolerance index (TOL) and stress susceptibility index (SSI), indicating the importance of additive genetic effect. Significant mean squares of specific combining ability (SCA) were observed for all the studied traits except TOL indicating the importance of non additive genetic effects for them. Low narrow sense heritability estimates for Pp and Ps and also other associated stress indices except geometric productivity (GMP) indicated the prime importance of non additive genetic effects for these traits except GMP. Most of the crosses had significant SCA effects of siliquae per plant at non application of nitrogen condition, therefore selection of combinations based on SCA effect of Ps will be more efficient than SCA effect of Pp. The variations of SCA effects of the crosses for mean productivity (MP) and GMP are higher than the other stress indices, so selection of the crosses based on this two stress indices will have sufficient gain. High parent heterosis effects of TOL, STI and SSI were more variated than SCA effects, therefore selection based on high parent heterosis effects will be more efficient than SCA effects.