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Oral: Fungal Genomics


Elucidating the genetic basis of race differentiation in Cercospora sojina through genotype-by-sequencing approaches
S. SHARMA (1), B. Dhillon (1), A. Fakhoury (2), B. Bluhm (1) (1) University of Arkansas, U.S.A.; (2) Southern Illinois University, U.S.A.

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Cercospora sojina, the causal agent of frogeye leaf spot (FLS), is a widespread pathogen of soybean in the United States. Recently, a race structure was proposed for C. sojina based on susceptibility vs resistance responses of 12 soybean differential cultivars. We hypothesize that the delineation of races in C. sojina is attributable to variation in effector gene complements among individual isolates. To test this hypothesis, we devised a genotype-by-sequencing strategy for C. sojina to facilitate association mapping of loci associated with race structure. We developed a restriction-site associated DNA sequencing (RAD-seq) approach to cost-effectively genotype large numbers of C. sojina isolates, with the ultimate goal of identifying single nucleotide polymorphisms (SNPs) for association mapping. Bulk segregant analysis was performed with two pools of C. sojina isolates (48 isolates per pool, selected based on resistant or susceptible reaction on soybean cultivar UA5612). Ion Torrent PGM sequencing identified 15,158 SNPs, and candidate pathogenicity genes were identified based on differences in SNP density and non-synonymous SNPs between the resistant and susceptible pools. Elucidating the genetic basis of race structure in C. sojina will accelerate the development of DNA-based assays to differentiate races of the pathogen, and contribute to the fundamental understanding of genetic mechanisms underlying FLS.