Genome-wide association mapping of anthracnose (Colletotrichum sublineolun) resistance in the U.S. sorghum association panel

Authors: Cuevas, Hugo; Prom, Louis; COOPER, ELIZABETH - Clemson University; Knoll, Joseph - Joe; Ni, Xinzhi

Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2018
Publication Date: 3/29/2018
Citation: Cuevas, H.E., Prom, L.K., Copper, E.A., Knoll, J.E., Ni, X. 2018. Genome-wide association mapping of anthracnose (Collectotrichum sublineolun) resistance in the U.S. sorghum association panel. The Plant Genome. 11:170099.

Interpretive Summary: The identification of sorghum accessions resistant to anthracnose in temperate adapted germplasm is imperative to sustain productivity and profitability in the U.S. To achieve this goal, 335 temperate-adapted accessions of sorghum representing genetic diversity from public and private breeding programs were evaluated for anthracnose resistance response and resulted in the identification of 75 resistant accessions. Phylogenetic analysis suggest the presence of multiple resistant sources that could be strategically used in breeding programs to increase resistance durability. Three resistance locus at chromosome 5 and two at chromosome 1 were detected through genome-wide association analysis and can help breeders to introgress these resistance genes into elite breeding lines.

Technical Abstract: The productivity and profitability of sorghum [Sorghum bicolor (L.) Moench] is reduced by susceptibility to fungal diseases such as anthracnose, which causes yield loss of both grain and biomass. A limited number of resistant accessions are present in temperate adapted germplasm, while resistant sources in exotic germplasm collections are not currently available for breeding programs. To characterize the genetic diversity of resistant lines currently available to breeders, 335 accessions from the previously genotyped sorghum association panel (SAP) were tested for anthracnose resistance. A total of 86 accessions were resistant, and phylogenetic analysis of these accessions showed the presence of high genetic diversity and multiple resistant sources. Genome-wide association scans (GWAS) were conducted using 268,289 SNPs to identify loci associated with the anthracnose resistant response. Two GWAS based on the quantitative and binary (resistant or susceptible) scoring of resistant response identified associations in chromosome 8 and 5, respectively, and the associated region in chromosome 5 was located with a previously mapped anthracnose resistant locus. Another GWAS limited to the Caudatum germplasm identified an association on chromosome 1 and the same previous association on chromosome 5. Candidate genes within these loci were not related to R-gene families, suggesting the resistant response is instead controlled by genes involved in signaling cascades and transcriptional reprograming rather than recognition of pathotype-associated molecular patterns. The strategic integration of exotic resistant germplasm into SAP will be needed to identify additional rare resistant alleles via GWAS.