Genetic and molecular regulation of flower pigmentation in soybean

Flower color is one of the key traits, which has been widely considered for genetic studies on soybean. A variety of flower colors, such as dark purple, purple, purple blue, purple throat, magenta, pink, near white, and white, has been identified in cultivated soybean (Glycine max). Out of the 19,649 soybean accessions deposited in the United States Department of Agriculture-Germplasm Resources Information Network database, 67 % have purple flowers, 32 % have white flowers, and merely 1 % have flowers with different colors. In contrast, almost all accessions of wild soybean (Glycine soja) have only purple flowers. Flavonoids, mainly anthocyanins, are the most common pigments contributing to flower coloration in soybean. In the recent decades, the flavonoid biosynthesis pathway for anthocyanins has been well established, and some of the genes controlling flower color in soybean have been identified and characterized. Flower pigmentation of soybean is mainly controlled by six independent loci (W1, W2, W3, W4, Wm, and Wp) along with the combination of various other factors such as anthocyanin structure, vacuolar pH, and co-pigments. In this review, we summarize the current status of genetic and molecular regulation of flower pigmentation in cultivated and wild varieties of soybean.