Biochemical aspects of seedcoat colour inheritance in Phaseolus vulgaris L.

The influence was investigated of 2 gene pairs (V-v ^laeand Sh-sh) and a multiple allelic series of 3 alleles (C ^r-C-c ^u) on pigment synthesis in the seedcoat of Phaseolus vulgaris. All 12 homozygous combinations were examined in pure lines. These lines were obtained from F ₂ offspring by visual selection. Each type possessed the basis gene P, which did not itself produce any colour but whose presence was needed for the activity of other genes influencing seedcoat colour.

As pigments 18 different flavonoid compounds were isolated and 15 of them identified.

The gene pair V-v ^laecontrolled the number of hydroxyl groups in the B ring of the compounds formed. V probably acted on a precursor from which all these compounds were synthetized. The number of hydroxyl groups in the B ring proved to influence the action of other genes, determining the heterocyclic part of structure.

The multiple allelic series C ^r-C-c ^ucontrolled the formation of anthocyanins or flavonol glycosides. With c ^unone of these compounds was formed. The role also of C and C ^rcould be traced. A hypothesis was put forward to explain the phenomena, not previously found in any plant species.

Sh controlled the formation of leuco-anthocyanidins and stimulated the production of anthocyanins and flavonol glycosides formed in the presence of C of C ^r. This was the first investigation in which a single gene had been found responsible for the production of leuco-anthocyanidins.