IDENTIFICATION AND APPLICATION OF A RANDOM AMPLIFIED POLYMORPHIC DNA MARKER FOR THE-I GENE (POTYVIRUS RESISTANCE) IN COMMON BEAN

The dominant inhibitor I gene has recently become a liability for common bean (Phaseolus vulgaris) cultivars infected with temperature-insensitive, necrosis-inducing strains of bean common mosaic virus (BCMV). Although cultivars with the I gene can be protected from hypersensitive lethality by recessive resistance genes, the most broadly effective resistance gene combination (land bc-3 genes) is difficult to identify due to epistasis (dominance with epistasis of bc-3/bc-3 over I/-; hypostasis). Our objectives were to identify a molecular marker linked to the I gene and to evaluate indirect selection with the marker to facilitate pyramiding of the I and bc-3 resistance genes. Pairs of near-isogenic lines with and without the I gene were screened with random decamer primers in the polymerase chain reaction to identify linked random amplified polymorphic DNA (RAPD) markers. A single RAPD marker was identified (OW13(690), generated by a 5'-CACAGCGACA-3' decamer) and found to be tightly linked in coupling with the I gene in five segregating populations (recombination from 1.3 +/- 0.8 to 5.0 +/- 2.2 centimorgans). Selections from complex backcross populations, made for the presence of bc-3/bc-3 genotypes, were also assayed for OW13(690) to identify selections carrying the hypostatic I gene. Our results demonstrate the utility of RAPD markers when used as indirect selection criteria for pyramiding epistatic BCMV resistance genes.