# Fine Mapping of the Co-12 Anthracnose Resistance Gene in the Andean Common Bean Cultivar in Brazil

## TL;DR

Researchers identified the location of the Co-12 gene in common beans, which helps resist anthracnose disease, and found new candidate genes involved in this resistance.

## Contribution

The study fine-maps the Co-12 resistance gene and identifies new candidate genes, including lipid transfer proteins, linked to anthracnose resistance in common beans.

## Key findings

- The Co-12 gene was mapped to chromosome Pv04 within a 41 kb interval.
- Three candidate genes, including two lipid transfer proteins (LTP2), were identified in the Co-12 region.
- LTP2 genes suggest a new resistance mechanism against anthracnose in common beans.

## Abstract

The common bean (Phaseolus vulgaris L.) cultivar Jalo Vermelho carries the Co-12 gene, which confers resistance to both Andean and Mesoamerican races of Colletotrichum lindemuthianum. Despite its importance for breeding programs, the genomic location and candidate genes underlying this resistance remain poorly defined. The Co-12 locus was fine-mapped using a biparental population derived from the cross Jalo Vermelho × Crioulo 159. A total of 172 F2 plants were used to generate 172 F2:3 families, which were phenotyped after inoculation with race 1545 of C. lindemuthianum. Segregation analysis confirmed a 1:2:1 Mendelian ratio, consistent with a single dominant resistance gene. Genotyping of resistant and susceptible plants using the BARBean6K_3 Illumina BeadChip (5398 SNP markers) mapped Co-12 to chromosome Pv04, between 1695 bp (ss715649768) and 9,651,954 bp (ss715646644). Subsequent fine mapping with simple sequence repeat (SSR) markers delimited the locus to a 41 kb genomic interval flanked by BARCPVSSR04557 and BARCPVSSR04570. Within this region, three candidate genes were identified, including one encoding a gamma-glutamyl-GABA enzyme and two encoding lipid transfer proteins (LTP2). Lipid transfer proteins are widely recognized components of plant defense; however, their association with anthracnose resistance in the common bean has not been previously reported. The identification of LTP2 genes within the Co-12 interval suggests a previously unrecognized resistance mechanism and expands the current understanding of host defense pathways in Phaseolus vulgaris. The markers identified here provide valuable tools for marker-assisted selection and will facilitate efficient introgression of Co-12 into common bean cultivars.