Genetic characterization of group A acetylsaponin-deficient mutants from wild soybean (Glycine soja Sieb. and Zucc.)

Group A acetylsaponins are the main causative components for bitter and astringent tastes of soybean (Glycine max). In this study, we examined the genetic nature of the absence of group A acetylsaponins in 12 Korean wild soybean (Glycine soja) accessions. In all 12 accessions, the coding region (1431-bp) of Sg-1 locus was identical with Sg-1^a, which adds the xylose sugar moiety at the terminal position of the C-22 sugar chain of SS-A, except one nucleotide (G→A change) at +948th position. This point mutation results in change of one amino acid from tryptophan (TGG) to stop codon (TGA). We observed that the mutated Sg-1 was controlled by a single recessive gene (sg-1^0-a1). This gene was mapped between BARCSOYSSR_07_1561 and BARCSOYSSR_07_1598 on soybean chromosome 7. Our study demonstrated that the mutated Sg-1 gene in Korean wild soybeans is genetically different from those identified in Japanese soybean cultivar 'Kinusayaka' and wild soybean JP-36121. We believe that the new Sg-1 mutants can also be utilized to produce a new soybean variety without bitter and astringent properties.