Seed phenotype and maturity groups as determinants of protein, oil, and fatty acid composition patterns in diverse soybean germplasm.

Soybean seed physical characteristics are crucial for quality assessment, but the link between these characteristics and biochemical composition across different maturity groups (MGs) remains unclear. This study examined the relationships between seed physical characteristics (color and weight) and biochemical constituents, including oil content (OC), protein content (PC), and fatty acid (FA) composition in 191 diverse soybean accessions across eight MGs (0-VII) at three locations over two years. The results indicated that black-seeded accessions demonstrated a notably higher average of PC (47.33%) and a lower average of OC (15.78%) in contrast to yellow-seeded varieties, which had an average PC and OC of 42.52% and 19.12%, respectively. In addition, larger seeds exhibited increased OC (19.15%) and OA levels (23.27%), whereas smaller seeds revealed higher concentrations of PC (44.23%), LA (55.06%), and LNA (8.53%). Multivariate analyses, including principal component analysis, clustering heatmap, and radar plot, demonstrated distinct clustering patterns, exhibiting unique compositional profiles closely linked to seed physical characteristics. Furthermore, MGs exhibited notable correlations with LNA (R² = 0.238) and OC (R² = 0.233), especially in black-seeded and large-seeded accessions. These findings elucidate the complex interaction between seed physical traits and biochemical composition, presenting significant implications for soybean breeding programs aimed at specific quality attributes.