Estimation of Combining Ability in Rapeseed (Brassica napus L.) Using Line ×Tester Cross Method

In order to study the general combining ability(GCA), specific combining ability (SCA) and heredity ability in rapeseed, eight genotypes were crossed using line×tester method. Fifteen hybrids together with eight parents were compared in RCBD with three replication during 2002-2003 at Agricultural Research Station of Bayekola, Mazandaran. Mean of squares of GCA and SCA were significant for many of traits indicating significant differences for GCA effects of parents and SCA effects of hybrids. Estimation of degree of dominance more than one, and low heritability for plant height, total number of pods per plant and seed yield, indicated over-dominance gene effect and prime importance of non-additive gene effect for controlling above mentioned traits. Thus, producing hybrid seed for utlization of non-additive gene effects of these traits will be fruitful. For number of days to maturity,1000-seed weight and oil percentage, additive gene effects were more important. Thus, breeding based on selection for these traits will be effective. Among parents, Quantum and Legae and among testers, Foseto had high significant GCA effect for seed yield and some other traits. Therefor, these genotypes can be used for seed yield improvement. Among crosses, Foseto × Legae had the highest seed yield and high amount of SCA effect for number of seed per pod, number of pods plant and 1000 seed weight. In general the crosses with high SCA effect for seed yield, had at least one parent with high GCA effect, thus selection based on GCA effect of seed yield can be effective for improving SCA effect of seed yield