Inheritance of anthracnose resistance in the common bean cultivar Widusa

Abstract

Snap bean (Phaseolus vulgaris L.) cultivar, Widusa, was crossed to Michigan Dark Red Kidney (MDRK), Michelite, BAT 93, Mexico 222, Cornell 49–242, and TO cultivars to study the inheritance of resistance to anthracnose in Widusa. The segregation patterns observed in six F₂ populations supported an expected 3R:1S ratio suggesting that Widusa carries a single dominant gene conditioning resistance to races 7, 65, 73, and 453 of Colletotrichum lindemuthianum, the causal organism of bean anthracnose. Allelism tests conducted with F₂ populations derived from crosses between Widusa and Cornell 49–242 (Co-2), Mexico 222 (Co-3), TO (Co-4), TU (Co-5), AB 136 (Co-6), BAT 93 (Co-9), and Ouro Negro (Co-10), inoculated with races 7, 9, 65 and 73, showed a segregation ratio of 15R:1S. These results suggest that the anthracnose resistance gene in Widusa is independent from the Co-2, Co-3, Co-4,Co-5, Co-6, Co-9, and Co-10 genes. A lack of segregation was observed among 200 F₂ individuals from the cross Widusa/MDRK, and among 138 F₂ individuals from the cross Widusa/Kaboon inoculated with race 65, suggesting that Widusa carries an allele at the Co-1 locus. We propose that the anthracnose resistance allele in Widusa be named Co-1 ⁵ as Widusa exhibits a unique reaction to race 89 compared to other alleles at the Co-1 locus. RAPD marker A18₁₅₀₀ co-segregated in repulsion-phase linkage with the Co-1 ⁵ gene at a distance of 1.2 cM and will provide bean breeders with a ready tool to enhance the use of the Co-1 ⁵ gene in future bean cultivars.