The pigmentation of seedling hypocotyl is important in the knowledge, at a very early stage, of success in the cross of plants differing in this aspect. Several genes, among which are W1, W2, W3, W4 and wm, have been recognized as controlling flower pigmentation, and many studies indicate that flower and hypocotyl colors are closely associated. Hartwig and Hinson (1962) put in evidence that hypocotyl of W1W3W4 genotypes is darker than that of W1w3W4 ones.
Olivieri, A. M.; Lucchin, M.; and Parrini, P.
"Research Notes : The monogenic and digenic control of hypocotyl and flower
color in soybeans,"
Soybean Genetics Newsletter: Vol. 7
, Article 24.
Available at: http://lib.dr.iastate.edu/soybeangenetics/vol7/iss1/24