Genome-wide association study of grain mold resistance in sorghum association panel as affected by inoculation with Alternaria alternata alone and Alternaria alternata, Fusarium thapsinum, and Curvularia lunata combined

Authors: Prom, Louis; Cuevas, Hugo; AHN, EZEKIEL - Texas A&M University; ISAKEIT, THOMAS - Texas A&M University; ROONEY, WILLIAM - Texas A&M University; MAGILL, CLINT - Texas A&M University

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2020
Publication Date: 6/30/2020
Citation: Prom, L.K., Cuevas, H.E., Ahn, E., Isakeit, T., Rooney, W., Magill, C. 2020. Genome-wide association study of grain mold resistance in sorghum association panel as affected by inoculation with Alternaria alternata alone and Alternaria alternata, Fusarium thapsinum, and Curvularia lunata combined. European Journal of Plant Pathology. 157:783-798. https://doi.org/10.1007/s10658-020-02036-3.
DOI: https://doi.org/10.1007/s10658-020-02036-3

Interpretive Summary: The most important disease of sorghum is grain mold, a complex disease associated with number of fungal pathogens. Yield losses of up to 100% can occur if susceptible lines are planted in areas with a lot of rains after grain maturity. A total of 377 lines from the sorghum association panel were treated with three different fungal species to determine their resistance. The results showed PI533871, PI576130, and PI656036 were resistant to grain mold and also the top-scoring SNPs were mapped to the nearest or a nearby annotated gene which has precedence for a role in host defense. This work is significant because it suggests these lines have potential for use in breeding, as well as for future tests to verify a role for these genes in active host defense.

Technical Abstract: A total of 377 sorghum association panel lines grouped into 10 subpopulations were evaluated for grain mold resistance by inoculating them with Alternaria alternata alone, a mixture of A. alternata, Fusarium thapsinum, and Curvularia lunata, and untreated control during 2010, 2013-2015 growing seasons at the Texas A&M AgriLife Research Farm, Burleson County, Texas. Each accession was evaluated at least twice. Eleven accessions exhibited grain mold severity ratings of 2 or less, indicating that they were resistant to highly resistant to the disease when challenged with A. alternata alone, 7 lines identified as such when inoculated with a mixture of A. alternata, F. thapsinum, and C. lunata, and 17 resistant lines were identified under the untreated control. Three lines PI533871, PI576130, and PI656036 exhibited resistant to highly resistant response to grain mold across treatments. Comparison for disease response among the 10 subpopulations evaluated in this study, accessions within subpopulation 4 had the lowest overall grain mold severity ratings, indicating that this subpopulation (zerazera/caudatum racial type) may harbor genes for grain mold resistance. A genome-wide association study with over 79,000 single-nucleotide polymorphic (SNP) loci from a publicly available genotype by sequencing dataset available for the SAP lines was conducted to identify genomic regions associated with grain mold resistance response based on the individual and combined treatments. In most cases, the top-scoring SNPs were mapped to the nearest or a nearby annotated gene has precedence for a role in host defense.