Genetic mapping of the resistance allele 'Co-52' to 'Colletotrichum lindemuthianum' in the common bean MSU 7-1 line

Anthracnose is a devastating fungal disease of common bean (Phaseolus vulgaris L.), the causal agent of which is Colletotrichum lindemuthianum. MSU 7-1 is a common bean breeding line that contains the Co-52 and Co-7 anthracnose resistance genes. In this study, phenotypic analyses were conducted in an F2 population derived from the Mexico 222 (S) x MSU 7-1 (R) cross that was inoculated with race 64 of C. lindemuthianum. Segregation analysis revealed a 3R:1S ratio, indicating that only Co-52 confers resistance to race 64 once the Co-7 gene has been defeated by this race. The molecular marker g12333250, in linkage group Pv07, was linked in coupling phase to Co-52 at a distance of 1.2 cM. The presence or absence of this marker was also determined in the G 2333, TU, H1 and PI 207262 cultivars. It was found that the g12333250 molecular marker was present in G 2333 and absent in the other cultivars. Because the allele and marker are physically linked in a cis configuration, the Co-52 resistance allele present in MSU 7-1 and G 2333 cultivars can be monitored with great efficiency using g12333250. These results will be very useful for breeding programs aimed at developing anthracnose-resistant bean cultivars via marker-assisted selection.