Identification and genetic mapping of a rust resistance gene on chromosome Pv04 in the common bean cultivar CNC using bulked segregant sequencing

Rust, caused by the fungus Uromyces appendiculatus , is one of the most significant diseases of common beans in the United States and worldwide. The identification and characterization of new rust resistance genes are essential for developing cultivars with broad and durable resistance. The black common bean cultivar Compuesto Negro Chimaltenango (CNC) exhibits broad resistance to most known races of the rust pathogen, still its resistance has not been fully characterized. To genetically characterize and map the resistance loci in this cultivar, we crossed it with susceptible cultivar UI114 and evaluated the F ₂ population for resistance against races 20-6 and 31-1 of U. appendiculatus . Our results showed that rust resistance in CNC for races 20-6 and 31-1 co-segregates and is conditioned by a single dominant gene. Whole genome sequencing-based bulked segregant analysis identified a genomic region on the proximal end of chromosome 4 associated with rust resistance in CNC. To further validate the identified region, molecular markers spanning this region were mapped on the complete F ₂ population. This further delimited the resistance locus in a genomic interval of 653.8 kb. The genetic mapping information and the molecular markers developed in this study will be helpful in developing rust-resistant cultivars of common bean.