CONCENTRATIONS OF WATER-SOLUBLE NITROGEN AND AMINO-ACIDS AS CRITERIA FOR DISCRIMINATING VEGETABLE-TYPE AND GRAIN-TYPE SOYBEAN CULTIVARS

Soybean (Glycine max (L,) Merr,) cultivars occur in two types, the veg etable-type (edamame) and the grain-type cultivars. This study was car ried out to examine the characteristics of accumulation of water-solub le nitrogen and amino acids in immature and mature seeds from these tw o types of soybean cultivars, Ten vegetable-type and thirteen grain-ty pe cultivars were grown in an upland field of Yamagata University, The immature seeds were sampled 30 to 40 days after flowering, Concentrat ions of the water-soluble nitrogen measured in 1991 were highly correl ated with amino acid concentrations measured in 1992, The immature see ds of the vegetable-type cultivars contained higher concentrations of seven free amino acids (asparagine, alanine, glutamic acid, arginine, serine, histidine and valine) than those of the grain-type cultivars. Based on concentrations of these amino acids in immature seeds, we cor rectly discriminated the vegetable-type and grain-type cultivars, indi cating that differences in amino acid concentrations in the immature s eeds were sufficient to distinguish the two types of soybean cultivars , Furthermore, the concentration of water-soluble nitrogen may be a si mple measure that represents concentrations of free amino acids, and c an thus be used as one of the selection indices in breeding programs o f the vegetable-type cultivars.