GENETIC VARIABILITY AND ASSOCIATION OF YIELD AND YIELD RELATED TRAITS IN SOYBEAN (Glycine max L.) GENOTYPES AT BOKO, EAST HARARGHE, ETHIOPIA

Abstract

Soybean (Glycine max L.) production is increasing as a multipurpose crop used for oil production, as balanced diet and industry prepared foods and export in Ethiopia, but its production is not common in East Hararghe. Very limited research was conducted on genetic variability of soybean genotypes in Eastern Hararghe. This research was conducted to assess genetic variability among soybean genotypes for yield and yield related traits, and to determine the associations of traits. The 61 introduced soybean genotypes and three check varieties were evaluated for 13 traits in 2023 in 8 x 8 simple lattice design at Boko in East Hararghe. The significant differences among soybean genotypes for all traits were evident from the results of analysis of variance. The grain yield of genotypes ranged from 470.76 to 2727.62 kg ha-1 with a mean of 1488.06 kg ha-1 . Six introduced genotypes produced higher (2168.301 to 2727.62 kg ha-1 ) than yield of Maya variety (2078.86 kg ha-1 ) that produced highest yield among check varieties. The genotypic (GCV %) and phenotypic (PCV %) coefficient variations ranged from 5.45 to 38.84 and 9.84 to 39.44%, respectively, whereas estimate of heritability in broad sense (H2%) for 13 traits ranged from 30.72 to 96.97% and genetic advance as percent mean (GAM) ranged from 6.23 to 78.9%. High and moderate GCV, PCV, H2 and GAM (%) were estimated for all traits except pod length and days to maturity. This indicated close correspondence between the genotype factors and phenotype expression of the genotypes for these traits and the selection of high performing genotypes could be possible to increase the mean of selected genotypes as compared to the base population. Grain yield had positive and significant correlation with days to maturity, plant height, pod per plant, number of seed/plant, number of branch per plant, number of pods per cluster, number of clusters per plant and hundred seeds weight at both genotypic and phenotypic levels. Hundred seeds weight, number of pods per plant, plant height and number of seeds/plant had moderate and positive direct effects on grain yield at genotypic level indicated the true relationship of these traits and yield suggested simultaneous selection was possible to increase the yield and these traits in soybean genotypes. The first four principal components with Eigen values >1 accounted for about 71% of the total variation observed among genotypes. The 13 traits each had small contribution to the total variability of genotypes suggested all traits could be used to group genotypes in different clusters. The genetic distance for all possible of pairs 64 soybean genotypes ranged from 3.02 to 13.89 and the genotypes were grouped into eight distinct clusters. Cluster VI, III and I consisted of 18, 10 and 9 genotypes, respectively, and these clusters accounted 57.81% of the genotypes and the other five clusters consisted of 3 to 8 genotypes. The four clusters, Cluster VIII, VII, III and I consisted 27 (42.19%) of the genotypes and had higher mean grain yield in the range between 10.94 and 22.39% than the overall mean yield of genotypes. The mean genotypes in these clusters was also higher than the overall mean of genotypes for most of agronomic traits and had higher inter-cluster distances between each other and with other four clusters suggested the development of varieties is possible by selection and/or crossing of genotypes from these clusters. The research results suggested the possibility of developing varieties for high yield and agronomic traits through selection and/or crossing of distant genotypes and further evaluation to East Hararghe.