Genetic Analysis of Agronomic and Physiologic Characteristics in Rapeseed (Brassica napus L.) under Drought Stress and Non-stress Conditions

To estimate combining ability and genetic parameters for some agronomic and physiologic characteristics, a reciprocal diallel experiment was conducted with nine rapeseed (Brassica napus L.) varieties. Parents and their F1's were sown in drought stress (S) and non-stress (NS) environments using 9 × 9 lattice design with two replications at the Dryland Agricultural Research Institute, Sararood, Kermanshah, in 2015-2016 cropping season. Results showed that effect of general and specific combining ability (GCA and SCA), and reciprocal crosses (REC) were significant (P < 0.01) for most traits in both environments. Parents Shiralee for seed oil content (SOC), Comet and Dalgan for seed yield (SY) were the best general combiners while cross RGS003 × Licord was the best specific combination for thousand seed weight (TSW), relative water content (RWC), SOC, and SY in both environments. Additive genetic variance was more important component for days to flowering, plant height, silique length, TSW and SOC in both environments, while dominance gene effect was greater than the additive component for SY (both environments), number of siliques/plant (NSP), RWC and leaf temperature (S) and electrolyte leakage (NS). According to the results of the graphical analysis, the gene action for most traits was partial dominance, while it was over-dominance for NSP (S), RWC and SY (NS). Maximum and minimum of narrow-sense heritability were obtained for TSW (0.92, in S) and RWC (0.21, in NS), respectively. This study showed that it is possible to improve SY, SOC and other agronomic and physiologic traits through crossing between different varieties of rapeseed for both conditions.