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Title: A dominant gene for garnet brown seed coats at the Rk locus in Dorado common bean and mapping Rk to linkage group 1

item BASSETT, MARK - University Of Florida
item Miklas, Phillip - Phil
item CALDAS, G - International Center For Tropical Agriculture (CIAT)
item BLAIR, M - International Center For Tropical Agriculture (CIAT)

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2010
Publication Date: 9/17/2010
Citation: Bassett, M., Miklas, P.N., Caldas, G.V., Blair, M.W. 2010. A dominant gene for garnet brown seed coats at the Rk locus in Dorado common bean and mapping Rk to linkage group 1. Euphytica. 176:281–290.

Interpretive Summary: Bean seeds with red color testa represent red kidney and small red and other red-seeded dry bean market classes consumed worldwide. Uniform red color appearance is preferred by the consumer. Breeders trying to improve red-seeded culitvars for agronomic perfomance, disease resistsance, etc., have difficulty in recovering the acceptable red seed colors. This study investigated the genetics of red seed color for the small red seed class (also referred to as the Honduran small red seed class). It was found that the red seed color for the small red seed class was controlled by a new gene at the Rk (red kidney) seed color locus. The new gene named Rkr is dominant to Rk and conditions a garnet brown (dark red) seed color. Knoweldge of the genetics of seed coat color will enhance cultivar improvement for the small red seed class by helping breeders to recover the red seed appearance desired by consumers.

Technical Abstract: The color of the seed coats of Dorado (Phaseolus vulgaris L.) is garnet brown (dark red kidney bean color) and differs from most other dry bean varieties in the Honduran red bean market class. A genetic investigation of the color of Dorado (same as DOR364) and G19833 (Liborino market class) seed coats was conducted. Crosses with genetic tester stocks demonstrated that the gene for garnet brown (GB) in Dorado was not allelic with the R gene for dominant red (oxblood) seed coat. An allelism test between the Dorado gene for GB seed coat and the rkdrv gene for recessive expression of GB demonstrated allelism. We propose the gene symbol for Rkr for the Dorado GB seed coat color gene. Rkr expresses partial dominance over Rk, where Rkr/Rk expresses a paler and highly variable intermediate red color. The genotypes for the seed coat color were found to be P [C r] J G B v Rkr for Dorado and P [C Rst] J G b v Rk for G19833. Segregation analysis in the mapping population made up of DOR364 x G19833 recombinant inbred lines showed that the Rkr gene mapped to linkage group 1. The new allele at Rk was located at a distance of 17 cM from the RFLP marker Bng130 with a LOD >3.0. The genetics of the Liborino market class is discussed and a systematic presentation of the bracket convention for the [C R] locus is made. .