New Andean source of resistance to anthracnose and angular leaf spot: Fine-mapping of disease-resistance genes in California Dark Red Kidney common bean cultivar

Anthracnose (ANT) and angular leaf spot (ALS) caused byColletotrichum lindemuthianumandPseudocercospora griseola, respectively, are devastating diseases of common bean around the world. Therefore, breeders are constantly searching for new genes with broad-spectrum resistance against ANT and ALS. This study aimed to characterize the genetic resistance of California Dark Red Kidney (CDRK) toC.lindemuthianumraces 73, 2047, and 3481 andP.griseolarace 63-39 through inheritance, allelism testing, and molecular analyses. Genetic analysis of response to ANT and ALS in recombinant inbred lines (RILs) from a CDRK x Yolano cross (CY) showed that the resistance of CDRK cultivar is conferred by a single dominant loci, which we namedCoPv01(CDRK)/PhgPv01(CDRK). Allelism tests performed with race 3481showed that the resistance gene in CDRK is independent of theCo-1andCo-AC. We conducted co-segregation analysis in genotypes of 110 CY RILs and phenotypes of the RILs in response to different races of the ANT and ALS pathogens. The results revealed thatCoPv01(CDRK)andPhgPv01(CDRK)are coinherited, conferring resistance to all races. Genetic mapping of the CY population placed theCoPv01(CDRK)/PhgPv01(CDRK)loci in a 245 Kb genomic region at the end of Pv01. By genotyping 19 RILs from the CY population using three additional markers, we fine-mapped theCoPv01(CDRK)/PhgPv01(CDRK)loci to a smaller genomic region of 33 Kb. This 33 Kb region harbors five predicted genes based on the common bean reference genome. These results can be applied in breeding programs to develop bean cultivars with ANT and ALS resistance using marker-assisted selection.