EVALUATION OF GENETIC VARIANCE COMPONENTS FOR SOME QUANTITATIVE TRAITS IN RAPESEED (Brassica napus L.)

Three hybrid combinations obtained by crossing six winter rapeseed cultivars were analyzed for the impact of genes with additive and dominant effects and their interactions with inheritance of plant height and first lateral branch height. The linkage among the expected progeny means was checked using the scaling test method (Mather, 1949), while the estimates of genetic effects and mode of inheritance was made by the Generation Mean Analysis (Mather and Jinks, 1982). The additive dominant model did not prove adequate for plant height in all three crosses, and for first lateral branch height in the second and third cross. The inadequacy of the model showed epistatic gene effects were also of large importance in the inheritance of these traits. Duplicate epistasis for plant height inheritance was found in all three cross combinations and for inheritance of height of the first lateral branch in second and third cross combination. However, it should be emphasized that duplicate epistasis among dominant positive genes occurred on plant height inheritance in C1 and C3, and on inheritance of first lateral branch height in C3. Duplicate epistasis among dominant negative genes occurred in C2 on the mode of inheritance of both traits.