Phenomorphological Characterization and Genetic Diversity Assessment of Grain and Vegetable Soybean (Glycine max. (L.) Merrill) Lines for Breeding Advancements

Introduction: Vegetable soybean is emerging as a valuable crop due to its nutritional and economic benefits. However, its genetic and phenotypic diversity remains less explored com-pared to grain-type soybeans. This study aimed to evaluate the breeding potential of vegetable soy-beans through a comparative analysis of grain- and vegetable-type genotypes. Methods: Ten soybean genotypes (six vegetable-type and four grain-type) were characterized using phenotypic, reproductive, and genetic trait evaluations. Observations included growth stages, pod traits, and yield-related characteristics. Statistical analyses such as ANOVA, GCV, heritability es-timates, Principal Component Analysis (PCA), hierarchical and Tocher’s clustering, and Simple Sequence Repeat (SSR) marker analysis were conducted to assess trait variability and genetic di-versity. Results: Significant genotype-specific variation was observed. EC892880 matured fastest (R1-R7 in 37-57 days), while RKS-18 took 112 days. EC892882 exhibited the longest pod length (5.63 cm), and EC892880 had the highest number of pods per cluster (6.93). High genetic control was noted for days to 50% flowering (GCV: 27.42%, heritability: 99.89%) and test weight (GCV: 25.38%, heritability: 99.74%). PCA revealed that days to pod setting and maturity (R7) were the primary contributors to phenotypic variation, with PC1 and PC2 accounting for 84.5% of the total variance. Tocher’s analysis showed the highest genetic divergence (D² = 28,292.49) between Clus-ters II and III. Among 45 SSR markers, 41 were amplified but showed no polymorphism. Discussion: The results highlight substantial phenotypic diversity among genotypes, especially in maturity duration and yield-related traits, with some traits under strong genetic control. However, the lack of SSR polymorphism suggests limited molecular diversity, indicating the need for more robust genomic tools. Vegetable-type soybeans showed high intra-group similarity, which may limit genetic gain unless broader diversity is introduced. Conclusion: This study identifies key traits and diverse genotypes suitable for targeted breeding in vegetable soybeans. The findings emphasize the potential of phenotypic selection and highlight the urgent need for enhanced genomic marker development to facilitate molecular breeding efforts in vegetable soybean improvement.