Exploring seed and meal composition and protein solubility in soybean genotypes from different domestication periods

Traditionally, commercial soybean breeding has focused on increasing seed yield by crossing elite cultivars and limiting the genetic diversity within commercial germplasm. Wild and ancestral soybean genotypes have higher seed protein concentrations than commercial ones. Different seed protein concentrations and compositions result in diverse functional properties of soybean meal, in particular solubility is important for beverages and protein isolates production. The objectives of our study were (i) to characterize seed protein concentration and composition in genotypes from different soybean domestication periods (types) and (ii) to evaluate the protein concentration and solubility profiles of the defatted meals obtained from these genotypes. Variation within seed and meal protein concentration, composition, and solubility was evident along the domestication process. Wild relative (G. soja) and Elite genotypes had the maximum and minimum seed protein concentrations, respectively (42.9 and 36.3 g 100 g⁻¹). Soybean meal protein concentrations were 55.1, 47.7, 48.4 and 44.1 g 100 g⁻¹ for Wild relative (G. soja), Asian landraces, North American (Nam) ancestors and Elite, respectively. Ample genotypic variation was observed for β-conglycinin components, such as for β, α, and α′ subunits and for total glycinin and its components. Asian landraces had the highest protein solubility. Wild and ancestral germplasm are a reservoir of useful traits to improve soybean seed quality. This study opens the gates to the introduction of ancestral germplasm to breeding programs focused on protein quality and functionality.