Combining ability analysis of plant height and yield components in spring type of rapeseed varieties (Brassica napus L.) using line × tester analysis.

Line ×tester of six lines and two testers of spring rapeseed (Brassica napus L.) cultivars were used to estimate general combining ability (GCA), specific combining ability (SCA) effects, high parent heterosis and narrow-sense herita- bility estimate for plant height, yield components and seed yield. Significant variance of line x tester for pods per plant and seed yield, indicating non additive genetic effects have important role for controlling these traits. Significant mean squares of parents vs crosses which are indicating significant average heterosis were also significant for all the traits except seeds per pod. High narrow-sense heritability estimates for all the traits except seeds per pod exhibited the prime importance of additive genetic effects for these traits except seeds per pod. Most of the crosses with negative SCA effect for plant height had at least one parent with significant negative or negative GCA effect for this trait. For most of the traits except pods per plant, the efficiency of high parent heterosis effect was more than SCA effect for determining superior cross combinations.