Analysis of Flavonoids in Flower Petals of Soybean Flower Color Variants

We previously identified two anthocyanins, malvidin 3,5-di-O-glucoside and delphinidin 3,5-di-O-glucoside, in flower petals of soybean cultivars with purple flowers, 'Harosoy' and ''Clark'. However, two other anthocyanins found by high performance liquid chromatography (HPLC) analysis could not be identified. We further evaluated the effects of flower color genes W1, W3, W4, and Wm on flavonoid components using near-isogenic lines for these genes. The first objective of this study was to determine the two unidentified anthocyanins in flower petals of Clark. The second objective was to evaluate the effects of Wp for pink flower and W2 for purple-blue flower on flavonoid biosynthesis using purple-blue flowered cultivars Nezumisaya, Yogetsu-1-blue, and w2-20, and a pink flowered line LD05-15019-pink. Chemical analysis revealed that the two remaining anthocyanins were petunidin 3,5-di-O-glucoside and delphinidin 3-O-glucoside. Composition and amount of flavonoids in purple-blue flowers were generally similar to those of Clark suggesting that anthocyanin structure or copigmentation with other flavonoids may not be responsible for the color. Pink flowers contained 72% of total anthocyanins, 9% of the total flavonol glycosides, and 28% of aromadendrin 3-O-glucoside relative to Clark. Further, pink flowers lacked kaempferol 3-O-glucoside. It is uncertain whether the reduction in flavonol glycosides in combination with lower anthocyanin levels might fully explain the low intensity of pigmentation in pink flowers.