Genetic architecture of yield and yield components in rapeseed (Brassica napus L.)

The present investigation "Genetic architecture of yield and yield components in rapeseed (Brassica napus L.)" was carried out to study the extent of genetic variability in the material, nature of interelationship among various quantitative traits alongwith their heritability and expected genetic gain. Diallel analysis over environments was carried out to characterize the nature of combining ability variances and effects together with the nature and magnitude of gene action involved in the expression of various traits. Component as well as graphical analysis of FI and F2 progenies was also undertaken to study the nature of various genetic parameters. The materials comprised ten parents, their 45 F1’s and 45 F2 progenies generated in diallel fashion). The mean squares due to progenies were highly significant in F1 and F2 diallel hybrid progenies for all the traits under study except for primary branches per plant in FI and F2 generations, and for secondary branches per plant in, F1 generation. The heritability estimates in broad sense were. higher than the corresponding heritability estimates in narrow sense for all the traits except plant height. The heritability estimates (broad sense) were high for days to 50% flowering, siliquae on main raceme, siliquae per plant, seeds per siliqua, 1,000-seed weight, seed yield per plant and oil content; medium for days to maturity and low for plant height. The estimated genotypic correlation coefficients were higher in magnitude in comparison. to their corresponding phenotypic correlation coefficients. Among the developmental traits, days to 50% flowering exhibited highly significant positive correlation with days to maturity at .both genotypic and phenotypic levels, whereas, plant height had significant positive association with siliquae on main raceme, siliquae per plant, seeds per siliqua at genotypic level, but positive and significant association with siliquae on main raceme at phenotypic level only. Oil content exhibited positive significant association with 1,000-seed weight. The combining ability analysis carried over environment, revealed significant mean squares for general combining ability and specific combining ability for all the characters studied in both the generations except for seed yield per plant for which mean squares due to general combining ability in F2 generation were non-significant. The components of variance revealed preponderance of sca variances for all the traits in both FI and F2 generations. The study of sca effects revealed that none of the crosses was a good specific combiner for all the characters in both the generations. The estimates of narrow sense heritability were moderate to low for the traits under study in both the generations. However, the estimates of heritability in narrow sense were less in magnitude in F2 generations as compared to corresponding estimates in F1 generations. The implications of breeding methodology and the lines identified for further utilization from the present set of materials have been discussed