Soybean is a vital legume with significant nutritional and economic importance, contributing to global edible oil and protein supplies. In Nepal, soybean cultivation is expanding, yet its performance varies due to environmental heterogeneity and genotype-environment interaction. In the present study, the performance of 18 soybean genotypes over 5 locations during the rainy season of 2019 and 16 soybean genotypes over locations during the rainy season of 2020 was carried out in an alpha lattice design and investigated using AMMI and GGE biplot analysis to assess adaptability and stability using combined ANOVA, AMMI, and GGE biplot analyses. In 2019, environment contributed the most to variation in grain yield (27.84%), followed by genotype x environment interaction (55.31%) and genotype (16.83%). Conversely, in 2020, environment explained 65.8% of the variation, with genotype contributing only 5.14% and genotype x environment interaction 29.04%. Overall, the combined analysis revealed that genotype x environment interaction was a significant source of variation, particularly in 2019. The GGE biplot effectively visualized the relationships between locations and genotypes, with the first two principal components explaining 81.22% of the variation. It identified superior genotypes such as G-1873, TGX-1445-ID, and SB0122 in terms of high grain yield. Notably, G-1873 was closest to an ideal genotype, exhibiting both high yield and stability. The “Which-Won-Where” analysis grouped the testing sites into two mega-environments: one with three locations where G-1873 was the top performer, and another with a single location where GC8234GC-13 excelled. Locations like Surkhet, Salyan, and Doti were identified as the most suitable for soybean cultivation, being closest to the ideal in the concentric circle representation. Overall, the findings provide valuable insights for soybean breeding programs aimed at improving yield stability and adaptability across diverse environments in Nepal. The identification of location-specific genotypes will facilitate targeted cultivar development and deployment, ultimately supporting Nepal’s soybean industry and reducing reliance on imports.
