Genetic variability and character association in soybean (Glycine max L. Merrill) genotypes

Abstract

Information on the extent and pattern of genetic variability, interrelationship among different agronomic characters and knowledge of diversity are essential to design breeding strategies in the available germplasm of soybean and helps to identify elite genotypes that will be incorporated into soybean crop improvement programs to address the growing demand of the crop in Ethiopia. Forty-nine soybean (Glycine max (L.) Merrill) genotypes were tested in 7x7 simple lattice design at Jimma and Assosa with the objectives of estimating genetic variability and associations among characters, and to estimate genetic divergence and, thereby, to cluster the test genotypes into genetically divergent classes. Analysis of variance revealed that there was statistically significant difference among the forty nine genotypes for most of the traits studied except root volume and root dry weight at Jimma. The relatively wide range of the mean values for most of the characters indicated the existence of variations among the tested genotypes. High phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) was recorded for grain yield, biomass yield, pod number per plant, plant height, total nodules per plant, effective nodules per plant, and harvest index at both locations. The highest heritability value was recorded for grain yield at both locations. High heritability, coupled with high expected genetic advance as percent of mean, was observed for grain yield, harvest index, biomass yield, total nodules per plant, effective nodules per plant and pod number per plant across both locations. This indicates that the characters can be improved through selection. Days to 50% flowering, days to pod setting and days to maturity showed negative and significant genotypic and phenotypic association with grain yield at Jimma. Grain yield was negatively and significantly correlated with biomass yield, pod number per plant and hundred seed weight both at genotypic and phenotypic levels at Assosa. Genotypic path analysis revealed that effective nodules per plant and pod number per plant at Jimma and Assosa, respectively exerted the highest positive direct effect. The D2 analysis grouped the 49 soybean genotypes into five and three distinct clusters at Jimma and Assosa, respectively. The principal component analysis revealed that 6 and 5 principal components at Jimma and Assosa, respectively have accounted for 79.90% and 73.81% of the total variation, respectively.