Genetic analysis of plant height, yield components and seed yield in rapeseed (Brassica napus L.) cultivars

Half F2 diallel crosses of spring rapeseed (Brassica napus L.) varieties along with their parents were evalu- ated for plant height, first siliqua height, siliquae on main axis, siliquae per plant, 1000-seed weight and seed yield. The Analysis of variance based on Cockerham’s method revealed significant mean squares of general combining ability (GCA), specific combining ability (SCA) for all the traits indicating that both additive and non-additive genetic effects were involved in controlling these traits. Parent vs crosses mean square which is indicating average heterosis was significant for all the traits. In Hayman’s method the regression lines esti- mated for all the traits except plant height cut the Wr axis below the origin in the negative zone, suggesting the overdominance type of gene action for these traits except plant height. Based on the array points on the regression lines, 19H had maximum dominant genes for siliquae on main axis, siliquae per plant 1000-seed weight and seed yield, being closest to the origin, while Option500 possessed recessive genes for first siliqua height, siliquae per plant and 1000-seed weight, as evidenced by its distant position from the origin. Due to low narrow-sense heritability estimates for most of the traits, selection for improving these traits should be carried out in delayed segregating generations.