IMPROVEMENT OF SOME ECONOMIC TRAITS IN CANOLA (BRASSICA NAPUS L.) USING DIFFERENT SELECTION PROCEDURES

摘要

Some selection procedures i.e. selection index involving three indices and pedigree line selection for two separately traits (seed yield/plant and seed oil content) were used to improve seed yield and yield components in early segregating generations; F_2, F_3 and F_4 of the canola cross (Line 99 x Serw 4). Mean performances of F_4 generation were higher than those of F_3 for seed yield/plant, oil seed content, 1000 seed weight and plant height. The highest predicted genetic advance from F_3 generation and exceeded 35% of the F_3 mean was obtained with the indices I_(w1), ped_(.w) and I_(w123). These indices maintained the same trend in F_4 generation as the highest realized and predicted advances as values and percentages (more than 23% and 18% of F_4 mean, respectively). Deviations of the realized advance from the predicted of seed yield determined in F_3 to F_4 generation were negative for selection index involving oil seed content and number of racemes/plant and pedigree selection for oil seed content. These results showed that the genetic variations for seed yield in early generations did not be exhausted enough and the improvement of seed yield/plant could be continued in further generations using direct pedigree selection for seed yield/plant and the indices I_(w123) and I_(w1). High heritability estimates were recorded for all the studied traits with higher values in F_4 generation than those of F_3 generation, except for seed yield/plant, indicating high magnitude of genetic variability and a possible success in the selection of the early generations. The values of phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) in F_4 were higher than those of F_3 generation for most studied traits, this indicated that the magnitude of the genetic variability continued in these materials was sufficient for providing rather substantial degrees of improvement through the selection of superior progenies. Seed yield/plant showed positive and highly significant phenotypic and genotypic correlations with number of racemes/plant in F_3 generation, positive and significant or highly significant phenotypic correlation with number of racemes/plant and 1000 seed weight in F_4 generation and positive and highly significant genotypic correlation with 1000 seed weight in F_4 generation. The path coefficients of seed yield with its components were changed from F_3 to F_4 generations. This could be due to the efficiency of selection procedures applied in this study.