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

Abstract

A total of 377 lines from Sorghum Association Panel (SAP) grouped into 10 subpopulations based on eight phenotypic traits, including flag leaf width, terminal branch length, flag leaf height, and flowering time and genetic data 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 water-sprayed 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. When the 10 subpopulations were compared for disease response, accessions within subpopulation 4 had the lowest overall grain mold severity ratings, indicating that this subpopulation (zerazera/caudatum racial type) harbors genes that may contribute to 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 with precedence for a role in host defense.