CHARACTERIZATION OF THE GENETIC-RESISTANCE TO COLLETOTRICHUM-LINDEMUTHIANUM IN COMMON BEAN DIFFERENTIAL CULTIVARS

The inheritance of genetic resistance to bean anthracnose in genotypes Catrachita and SEL 1360 derived from two anthracnose differential cul tivars, AB 136 and G 2333, respectively, is described. Segregation dat a from three different F-2 populations and their respective F-2:3 fami lies indicated that a single dominant gene is responsible for the anth racnose resistance in Catrachita. In the test for allelism, chi-square test confirmed that the single dominant resistance gene in Catrachita was situated at a different locus from previously characterized resis tance genes A, Are, Mexique 1, Mexique 2, and Mexique 3. It is propose d that the single dominant resistance gene present in Catrachita be as signed the genetic symbol Co-6, Co for Colletotrichum and 6 because it is the sixth major anthracnose resistance gene characterized and repo rted in the literature. Segregation in the three F-2 populations where SEL 1360 was used as the resistant parent fitted a 3:1 (R-:rr) ratio and a 1:2:1 (RR:Rr:rr) ratio in the F-2:3 families. Segregation data s uggested that a single dominant gene was conditioning resistance to an thracnose in SEL 1360. The test for allelism involving SEL 1360 indica ted that the single dominant gene in SEL 1360 is independent from A (C o-1), Are (Co-2), Mexique 1 (Co-3), and Mexique 2 (Co-4) genes. Howeve r, the dominant gene in SEL 1360 did not segregate independently from the resistance gene Mexique 3 in the differential cultivar TU, demonst rating that both dominant alleles are located at the same locus. Deplo yment of major genes of Middle American origin, such as Co-6 and Mexiq ue 3 (Co-5), in different combinations with other characterized genes of Andean origin is possible and should contribute to more durable ant hracnose resistance in common bean.