Molecular Genetic Analysis of a Novel Recessive White Flower Gene in Wild Soybean

Cultivated soybean [Glycine max (L.) Merr.] flowers are either white or purple, whereas nearly all wild soybean (G. soja Sieb. and Zucc.) accessions have purple flowers. As a result, the soybean flower color phenotype has attracted the attention of plant breeders, biochemists, and population geneticists. Here, we report genetic mapping of a novel recessive white flower gene in YWS415, a wild soybean accession collected in Korea. The W1 locus, which is the major locus determining purple (W1) or white (w1) flower color, encodes flavonoid 3′ 5′-hydroxylase in YWS415, which was more similar to the common W1-type sequences than w1-type sequences. Subsequent mapping results using an F₂ population from a cross between the ‘Hwangkeum’ (purple flower) and YWS415 variants indicated that the white flower color was controlled by a recessive allele at the W4 locus that encodes dihydroflavonol-4-reductase 2 (DFR2). The w4 allele arose through insertion of a 5584-bp nonautonomous transposon member of soybean GM_CACTA_33 family into the second intron of DFR2. It was designated as GM_CACTA_33_w4. Results from this study will enhance our understanding of soybean white flower inheritance and facilitate marker-assisted selection for the antioxidative anthocyanins in soybeans.