Inheritance and Allelism of a New Low-Stachyose Soybean Mutant.

Sucrose, raffinose, and stachyose constitute the major soluble sugars in soybean seed. Sucrose favorably influences the quality and flavor of soyfood products, whereas raffinose and stachyose reduce their digestibility. A breeding line (V99-5089) developed by Virginia Tech has been identified as having reduced stachyose content. The objectives of this study were 1) to determine the number of genes controlling the low-stachyose trait, and 2) to investigate the allelomorphic relationship between the new mutant gene(s) and a previously reported recessive gene in PI 200508.  For objective 1, 123 F_2:3 lines from V97-3000 x V99-5089 (normal stachyose x low stachyose) were grown at 2 locations with 2 replications in 2008. For objective 2, 126 F_2:3 lines from PI 200508 x V99-5089 (low stachyose x low stachyose) were grown at 1 location with 2 replications in 2008. A seed sample from each plot was analyzed for soluble sugar content with a high performance liquid chromatography (HPLC) system. Chi-square analysis was used to test goodness-of-fit of observed segregation to expected genetic ratios. Results showed a single recessive gene responsible for the low-stachyose content in V99-5089. This gene is non-allelic to the recessive gene (stc1a) reported in PI 200508. A gene symbol stc2a is proposed for the new locus conferring low-stachyose content in V99-5089. The new mutant gene in V99-5089 offers an option for breeders to use in breeding for low-stachyose soybean.