Inheritance and Characterization of a Null Allele for Group A Acetyl Saponins found in a Mutant Soybean (Glycine max (L.) Merrill)

Abstract

A total of 801 cultivated soybean accessions and 330 wild soybean accessions were screened for genotypes lacking group A acetyl saponins in seed hypocotyls using thin layer chromatography and high performance liquid chromatography. Only one accession from the soybean cultivars, A-b(F) Iacked group A acetyl saponins but it had an unknown saponin. The inheritance of a null allele for group A acetyl saponins in soybeans was determined by crosses between A-b(F) and Shirosennari, which had group A acetyl saponin Aa, and Suzuyutaka, which had group A acetyl saponin Ab, respectively. All F₁ seeds from these crosses had Aa and Ab respectively. F₂ seeds resulting from these crosses segregated 3:1 indicating that the absence of group A acetyl saponins is inherited as a simple recessive. The gene symbol Sg-1 is assigned to the allele coding for the absence of group A acetyl saponins, Sg-1^a for the presence of group A acetyl saponin Aa and Sg-1^b for the presence of group A acetyl saponin Ab, respectively. Sg-1^a and Sg-1^b are co-dominant alleles. Through FAB-MS and chemical analyses, the unknown saponin accumulated in the seed hypocotyls of A-b(F), was assumed to be 3-O-[β-D-glucopyranosyl-(1→2)-β-D-galactopyranosyl-(1→2)-β-D-glucuronopyranosyl]-22-O-[α-L-arabino-pyranosyl] soyasapogenol A.