MORPHOLOGICAL CHARACTERIZATION, VARIABILITY AND DIVERSITY AMONG SOYBEAN (Glycine max (L.) MERRILL) GENOTYPES IN SOUTH OMO ZONE, SOUTHERN ETHIOPIA

Abstract

Soybean [Glycine max (L.) Merrill] is one of the industrial crops of low- to medium-altitude legume crops that require a warm climate. Despite its high nutritional value, including 40% protein and 20% oil content, soybean productivity in Ethiopia lags behind the global average due to a lack of improved high-yielding varieties resistant to diseases and adaptable to stress conditions. Therefore, the study was conducted on 81 soybean genotypes with the objective of identifying morphological characteristics, genetic variability, and diversity. The experiment was laid out in 9x9 simple lattice designs at Jinka research site of southern Ethiopia in 2022 and 2023 July to October. Data were recorded for qualitative and quantitative traits and analyzed using appropriate statistical software SAS and R software. The result of the study showed that there were significant differences (P< 0.05) for the majority of the studied traits except for days to maturity among the tested genotypes. The variation observed among genotypes for grain yield ranged from 1238.33-2531.67 kg/ ha. Genotypes G-50, G-48, G 39, G-16, and G-15 showed superior performance compared to others, with the top three genotypes outperforming the standard check Gazela. The estimates of genotypic coefficient of variation (GCV), and phenotypic coefficient of variation (PCV) were high for plant height, seed per pod, pod length, pod per plant, branches per plant, hundred seed weight and yield per hectare, suggesting selection could be effective based on this traits.. High estimate of heritability was observed from 73.45% for seeds per pod and 92.25% for hundred seed weight. Expected genetic advances as a percent of mean (GAM) ranged from 8.39% for days to maturity to 71% for pods per plant. traits like hundred seed weight, plant height, pod length, pod per plant exhibited heritability coupled with high genetic advance as percent Grain yield showed a positive and highly significant correlation with hundred seed weight, number of branches per plant, yield per plot, pod per plant, both at the phenotypic and genotypic level. Yield per hectare exerted the highest positive direct effect on grain yield both at genotypic and phenotypic level. Principal components analysis (PCA) revealed that the four principal components accounted for 68.58% with Eigen values higher than one. Cluster analysis grouped 81 genotypes genotype into five clusters. The highest inter-cluster distance was observed between cluster I and V (D2=388.4**) which indicated that chance of selecting a member of genotypes in these clusters for hybridization. The results of Shannon diversity index for eight qualitative traits indicated that the average diversity index was 0.527, indicating the existence of adequate diversity on the tested genotypes which could be exploited in breeding programs. In conclusion, the findings of this study revealed the presence of sufficient genetic variability in soybean genotypes and this variability should be exploited for future soybean improvement program.