Comprehensive Evaluation of Agronomic Traits and Nutritional Composition in Summer-Sown Vegetable Soybean Varieties from Shanghai, China.

Shanghai-native vegetable soybean (Glycine max [L.] Merril) landraces are valuable germplasms, but their systematic evaluation for agronomic and nutritional traits remains insufficient. This study aimed to assess their phenotypic and nutritional diversity to explore their potential for breeding and meeting dietary needs. Twenty-nine local landraces and one control cultivar ('Qingsu 7') were evaluated for key agronomic traits, yield components, nutritional traits, and isoflavone profiles, using hierarchical clustering, principal component analysis (PCA), and correlation analysis. Substantial phenotypic diversity was found, with the germplasm classified into four groups. First pod height and effective pods per plant were highly variable. Nutritional traits showed low variability for crude protein but high diversity for crude fat, soluble sugars (dominated by sucrose), vitamin C, and free amino acids. Total isoflavone content in dry seeds varied widely, with genistin, daidzin, and daidzein as the main forms. 'Xiangshui Maodou' had high free amino acids and vitamin C, 'Heiyan Susudou' showed superior soluble sugar content, and two landraces exceeded 1500 μg/g DW total isoflavones. The landraces possess rich phenotypic diversity and nutritional diversity. This germplasm represents a valuable resource for breeding programs to enhance crop quality and address global nutritional demands.