RESEARCH ARTICLE Fine Mapping and Characterization of Candidate Genes that Control Resistance to Cercospora sojina K. Hara in Two Soybean Germplasm Accessions

Frogeye leaf spot (FLS), caused by the fungusCercospora sojina K. Hara, may cause a sig-nificant yield loss to soybean growers in regions with a warm and humid climate. Two soy-bean accessions, PI 594891 and PI 594774, were identified to carry a high level of resistance similar to that conditioned by the Rcs3 gene in 'Davis'. Previously, we reported that the resis-tance to FLS in these two plant introductions (PIs) was controlled by a novel gene (s) on chro-mosome 13 that is different fromRcs3. To fine-map the novel FLS resistance gene(s) in these two PIs, F2: 3 seeds from the crosses between PI 594891 and PI 594774, and the FLS susceptible genotype 'Blackhawk ' were genotyped with SNPmarkers that were designed based on the SoySNP50k iSelect BeadChip data to identify recombinant events and locate candidate genes. Analysis of lines possessing key recombination events helped narrow down the FLS-resistance genomic region in PI 594891 from 3.3 Mb to a 72.6 kb region with five annotated genes. The resistance gene in PI 594774 was fine-mapped into a 540 kb re-gion that encompasses the 72.6 kb region found in PI 594891. Sequencing five candidate genes in PI 594891 identified three genes that have several mutations in the promoter, intron