A NEW ALLELE, RK(CD) WITH CONVERTIBLE EXPRESSION AT THE RED KIDNEY LOCUS FOR SEEDCOAT COLOR IN COMMON BEAN

Authors: BASSET, MARK - UNIV FL, GAINESVILLE; Miklas, Phillip - Phil

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2002
Publication Date: 2/1/2003
Citation: BASSET, M.J., MIKLAS, P.N. A NEW ALLELE, RK(CD) WITH CONVERTIBLE EXPRESSION AT THE RED KIDNEY LOCUS FOR SEEDCOAT COLOR IN COMMON BEAN. JOURNAL OF AMERICAN SOCIETY OF HORTICULTURAL SCIENCES, 128:552-558. 2003.

Interpretive Summary: Four of ten dry bean market types Pink, Small Red, Light Red Kidney, and Dark Red Kidney worth about $100 million in annual U.S. farm-gate value express red seedcoat color. Breeding less disease prone cultivars with higher yield is problematic for these red-seeded market classes because recovery of the red seed color is extremely difficult. Most crosses used to improve red beans result in progeny with brown seed, with or without a red hue. We initiated crosses among standard red-seeded cultivars of each market class. Two new novel genes, one with convertible and the other with weak expression at the red kidney locus for seedcoat color, were discovered. The genes condition red and pink seed colors, and help to explain the difficulty breeders have faced with recovery of commercially acceptable Pink, Small Red, Light Red Kidney, and Dark Red Kidney bean cultivars. Knowledge gained will lead to new red and pink bean cultivars with enhanced disease resistance and improved yield.

Technical Abstract: Among light red and dark red kidney common bean (Phaseolus vulgaris L.) cultivars, pink seedcoat color (light red kidney) is dominant to dark red, but when small red cultivars (with dark red seedcoats) are crossed with dark red kidney cultivars, dark red seedcoat is dominant to the pink segregants observed in F2. A genetic investigation of this ¿reversal of dominance¿ was performed by making crosses in all combinations among standard light red kidney `California Early Light Red Kidney¿, pink `Sutter Pink¿, small red `NW63', and dark red kidney `Montcalm¿ cultivars and observing segregation for seedcoat colors in F2 and F3 progenies. The data were consistent with the hypothesis that `NW63' carries a new allele at Rk, viz., rkcd, where cd stands for convertible dark red kidney. In the F2 progenies of BC2 to 5-593, the cu b v rk segregants from `Redkloud¿ gave true pink seedcoats, whereas those derived from `Sutter Pink¿ gave consistently very weak pink color under Florida growing conditions. We propose the gene symbol rkp, where p stands for pale pink, for the distinctive rk allele in `Sutter Pink¿. The more general implications of the above findings were discussed.