Assessment of genetic variability and diversity in soybean (Glycine max L.) germplasm from Myanmar

Abstract

Genetic variability within germplasm collections forms the foundation of effective crop improvement programs by providing essential resources for selection, adaptation, and yield enhancement. In Myanmar, soybean genetic resources conserved in the national seed bank are limited and largely composed of local landraces, many of which remain underutilized in formal breeding efforts. Therefore, this study aimed to characterize and quantify the extent of genetic diversity among soybean germplasm conserved in Myanmar in order to identify promising genotypes for future breeding programs. A total of 60 soybean accessions obtained from the Myanmar Seed Bank, together with five released check varieties (Yezin 3, Yezin 6, Yezin 12, Yezin 14, and Yezin 15), were evaluated during the post-monsoon season of 2024 at the Seed Bank Field, Department of Agricultural Research, Yezin, Nay Pyi Taw, Myanmar. The experiment was conducted using an augmented design. Genotypes were characterized for nine qualitative and twelve quantitative agro-morphological traits following soybean BI descriptors. Data were analyzed using analysis of variance, estimation of genetic variability parameters, correlation analysis, principal component analysis (PCA), cluster analysis, and descriptive statistics in R Studio version 4.5.1. The results revealed significant variation among genotypes for most traits, indicating the presence of substantial exploitable genetic diversity. The coefficient of variation ranged from 2.40% for number of seeds per pod to 24.28% for hundred seed weight, reflecting differential phenotypic stability among traits. High genotypic and phenotypic coefficients of variation (>20%), coupled with high heritability and high genetic advance as percent of mean, were observed for days to emergence, days to flowering, number of nodes on the main stem, plant height, and hundred seed weight, suggesting the predominance of additive gene action and the effectiveness of direct selection. Hierarchical cluster analysis grouped the genotypes into five distinct clusters, with Cluster V containing the largest number of genotypes, while Cluster IV consisted of a single highly divergent genotype. PCA indicated that the first six principal components accounted for 70.78% of the total variation, with yield-related and phenological traits contributing most to genetic divergence. Significant positive correlations among key traits further support the potential for simultaneous trait improvement. Overall, the substantial genetic diversity identified highlights Myanmar soybean germplasm as a valuable source of elite parental lines for the development of high-yielding and well-adapted cultivars.