Estimation of genetic parameters for some quantitative traits in large seeded bean (Phaseolus vulgarisL.) lines by factorial analysis of generation means
Understanding the nature of gene action in the breeding materials is helpful for breeders in formulating breeding strategy. In order to understand the type of gene actions operating in the breeding materials, six generation means (P1, P2, F1, F2, BC1 and BC2) from two crosses among large seeded bean lines grown at Awassa 2002 were used to estimate the genetic effects of some quantitative traits. The result revealed that for seed yield (gm/plant), pods/plant and pod length additive genetic model was not sufficient to explain most of the genetic variation for the expression of these traits. Epistatic effects contributed to the inheritance of these traits in the two crosses used. For seeds/pod and plant height epistatic gene effect was present in one of the two crosses. The nature of epistasis operating in the inheritance of seed yield (gm/plant), pods/plant, pod length, and plant height is duplicate type whereas it is complimentary type for seeds/ pod. This indicates that particular allelic combinations at several loci determine the performance of these traits. Thus, population improvement and gamete selection breeding methods may help to improve these traits. Realized heterosis (over mid-parent) was observed for seed yield(gm/plant), pods/plant and plant height in one of the two crosses with no inbreeding effect in F2 indicating that the heterosis is largely caused by non-allelic interaction even though over dominance was also observed. Pods/plant could be an important trait for plant selection in segregating generations as it revealed a significant positive correlation and high direct effect with seed yield.