Illustration of the effect of wp on flower and seed coat phenotypes. (A) Stable purple flower of plants with Wp genotype (left panel) or stable pink flower of plants with wp genotype (right panel) in lines LN89-5320-6 (iiRtW1Wp) and LN89-5322-2 (iiRtW1wp) both of which have yellow seed coats. In soybean I (CHS), R and T (F3'H) are three independent loci that control pigmentation in seed coats and W1 (F5'3'H) and Wp (F3H) were described as flower color markers, but all five loci seem to be encoding genes of the anthocyanin and proanthocyanidin pathways. Mutant alleles of those loci (i, ii, r, t, w1 and wp) affect flower, seed coat, hypocotyle or pubescence coloration [1, 28, 30, 31]. (B) Imperfect black color of seed coats of plants with iRtW1Wp genotype (left panel) as contrasted with the lighter shaded seed coats of plants with iRtW1wp genotype (right panel). Effect on the seed coat phenotype was revealed by crossing the wp allele into lines having the recessive i allele that allows spatial pigmentation of the entire seed coat . The cracks on both seed coat types result from an epistatic effect of t . (C) Black seed coats of plants with iRTW1Wp genotype where the T allele drives the synthesis of cyanidins (left panel) contrasted with the lighter seed coats of plants with iRTW1wp genotype (right panel). (D) Abbreviated schematic representation of the three branches leading to the synthesis of the three anthocyanin classes and the genes encoding the enzymes relevant to the present study.