Recurrent selection for broad-spectrum resistance to anthracnose in common bean

Recurrent selection is an effective and well-known breeding method recommended for quantitative traits. However, the method has not been applied so far for traits typically controlled by numerous major loci, which is the case of resistance to anthracnose in common bean (Phaseolus vulgaris L.). In this study, we report the effectiveness of a recurrent selection program in developing common bean progenies with resistance to multiple races of Colletotrichum lindemuthianum, the causal agent of anthracnose in this crop. A total of 10 common bean lines, with distinct and complementary resistance profiles to races 65, 73, 81, and 89 of C. lindemuthianum, were intercrossed to establish a base population (Cycle 0). From Cycle 0, five iterative cycles of recombination, inoculation, and selection were carried out. Our results demonstrate that this recurrent selection approach can effectively combine resistance in common bean to different isolates from multiple races of C. lindemuthianum. A progressive increase in the number of progenies resistant to a higher number of C. lindemuthianum isolates was observed over the selection cycles. The genetic gain from CI to CV was 38.75% when the progenies were evaluated against a mixture of isolates from the four races of the pathogen. The reliance on specific genes makes race-specific anthracnose resistance in common bean vulnerable to breakdown. By allowing optimal combinations of different anthracnose resistance genes, this dynamic recurrent selection approach is an attractive option for the development of common bean cultivars with increased stability and durability for anthracnose resistance.