Genetic Variability and Association of Traits in Soybean (Glycine max (L.) Genotypes in Ethiopia

Abstract

The study was conducted at Jimma andMetu, southwestern Ethiopia during 2019 main cropping season to estimate the extent of genetic variability  and association among traits in100soybeangenotypes(Glycine Max (L.). The field experiment was laid down in 10 x10 simple lattice design. The  combined analysis of variance revealed the presence of significant (P<0.01) and wide range ofvariation among the tested genotypes for most of the  traits. The maximum grain yield per hectare was recorded on genotypes; T1-EL-OS-JM17-E1, T4-EL-LG-65-JM17-A11 and T4-EL-LG-65-JM17-F2(2.50  t/ha each) while the minimum (0.85t/ha) was obtained from T5-EL-LD-77-JM17-D4.High yielding genotypes had a yield advantage of 32.98% and  61.29% compared with the standard checks (Nyala and Clark 63k), respectively. Subsequent combined high genotypic coefficients of variation (GCV),  high heritability (H2) and high genetic advance as present of mean(GAM) were recorded for plant height (24.80%, 87.85% and 47.95%), number of  pods per plant (25.34%, 69.38% and 43.55%) and hundred seed weight (20.74%, 75.29% 37.12%), which denotes, these traits can be improved  through direct selection more easily than other traits. Cluster analysis categorized 100 soybean genotypes into five clusters. The maximum inter  cluster distance was found between clusters-IV and V, suggesting superior recombinants can be realized by crossing genotypes in these clusters.  Principal component analysis (PCA) revealed that, the 1stfour PCA with Eigen values exceeding one were responsible for about 72.62 % of the total  variation. Out of the entire variations, 1stPCA and the 2ndPCA accounted for more than two third of the total variations (53.13%). Therefore,  discrimination of the genotypes into different clusters was mainly due to number of pod per plant, number of seed per plant, grain yield, plant  height, days to flowering, days to maturity and hundred seed weight. Grain yield exhibited significant (P<0.05) and positive phenotypic and  genotypic correlation coefficient to days to maturity, plant height , number of pod per plant, number of seed per plant, number of branch per plant and soybean rust. Except days to maturity and frog eye leaf spot, all other traits showed positive direct effect on grain yield. Number of pod per  plant and plant height showed positive direct effect and strong positive genotypic correlation coefficient with grain yield. Therefore, these traits  should be considered as important selection indices for yield improvement program. Generally, the present study revealed the existence of  enormous genetic variability among soybean genotypes for various important morphological traits.