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Title: Identification of Several gy4 Nulls from the USDA Soybean Germplasm Collection Provides New Genetic Resources for the Development of High-Quality Tofu Cultivars

item Nelson, Randall
item Krishnan, Hari

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2008
Publication Date: 11/8/2008
Citation: Kim, W., Ho, H., Nelson, R.L., Krishnan, H.B. 2008. Identification of Several gy4 Nulls from the USDA Soybean Germplasm Collection Provides New Genetic Resources for the Development of High-Quality Tofu Cultivars. Journal of Agricultural and Food Chemistry. 56:11320-11326.

Interpretive Summary: Soybeans are an excellent source of high-quality protein. They serve as the principal source of protein in China, Korea, Japan and other rice-consuming Asian countries. Tofu, which is made from soymilk, is widely consumed in these countries because of its high protein and low saturated fat content. Health-conscious consumers have started using tofu as a meat alternative in their diet since it has been shown to reduce the risk of coronary disease and the worldwide demand for tofu and other food-quality soybeans has increased. As a result, there is a great need to develop high quality soybean cultivars with desirable seed composition traits, while at the same time maintaining superior agronomic characteristics. Tofu quality is profoundly influenced by soybean seed protein composition. Superior tofu quality has been associated with the absence of certain proteins. Consequently, soybean breeders have utilized these protein mutants as donor parents in their breeding program for the development of commercial tofu cultivars. Repeated use of few genotypes in the breeding programs has resulted in a narrow genetic base which hampers effective improvement of agronomic and seed traits in the future. To expand the genetic diversity, it will be desirable to utilize genetically diverse parental lines for the development of high-quality tofu cultivars. In this study, we have identified several diverse storage protein mutants by screening soybean accessions from the USDA Soybean Germplasm Collection. The identification of these nulls provides an opportunity for US soybean breeders to exploit these mutants in developing high food-quality soybeans with a broad genetic base.

Technical Abstract: Tofu, a cheese-like food made by curdling soymilk, is a major dietary staple of Asian countries. Consumption of tofu and other soy products is steadily increasing in North America due to its well known health benefits. Soybean A5, A4 and B3 peptide null lines 'Enrei' and 'Raiden' are commonly utilized in breeding programs to develop high-quality tofu cultivars. To expand the genetic diversity it is desirable to identify and utilize other A5, A4 and B3 null genotypes in the development of improved tofu cultivars that are adapted to North American conditions. In this study, we have screened diverse soybean accessions from the USDA Soybean Germplasm Collection to identify Gy4 mutants, the locus that controls A5, A4 and B3 peptide production. Analysis of total seed proteins from 485 soybean lines by SDS-PAGE enabled the identification of 38 accessions that lacked the A5, A4 and B3 peptides. These accessions showed marked differences in seed size and seed coat color and represented different maturity groups ranging from 0 to IX. To ascertain the molecular basis for the lack of A5, A4 and B3 peptides in the newly identified Gy4 mutants, nucleotide sequence of a portion of the Gy4 gene was determined from eight soybean accessions representing different maturity groups. All the analyzed Gy4 mutants revealed a single point mutation that changed the translation initiation codon ATG to ATA resulting in the A5, A4 and B3 null phenotype. The newly identified Gy4 mutants from our study will enable plant breeders to expand the genetic diversity of North American food-quality soybeans and also aid in the development of hypoallergenic soybeans.