Genome-Wide Association Study for Grain Mold Resistance in Sorghum.

Grain mold (GM) is a globally important biotic constraint (panicle disease) of sorghum. Infection of this disease on sorghum panicles results in poor grain development with low seed quality, which ultimately limits yield and market value of sorghum grains. The complex interaction of host-pathogen-environment with polygenic inheritance and multiple mechanisms involved in GM resistance in sorghum makes breeding efforts challenging. Field experiments were conducted at Manhattan, Kansas in 2014 and 2015 growing seasons using 229 accessions of sorghum association panel (SAP) and screened for the major grain mold pathogen, Fusarium thapsinum under artificial inoculation following standard procedures. Agronomic traits [panicle grain mold rating (PGMR), thousand seed weight (TSW), glume length (GL), glume width (GW), days to flowering (DF) and days to physiological maturity (DPM) and kernel quality traits [total phenolic acids, total tannins (Tan), starch percent (SP) and 3-Deoxyanthocynanidins (3-Deo)] were used for the study. Genome-wide association study (GWAS) was performed to find associated quantitative trait loci (QTL) markers for GM resistance. A general linear model (GLM) and mixed linear model (MLM) considering kinship (K), and kinship and population structure (Q+K) were used to perform GWAS and Bonferroni correction at 0.05 level with P-value < 10^-7 was used to identify significant associations. Tannin 1 (tan-1) gene was used as positive control. Significant single nucleotide polymorphism (SNPs) were reported for the traits: PGMR, GL, GI, DF, DPM, Tan, Phe, TPP, SP, and 3-Deo.We reported two loci associated with grain mold resistance for PGMR at chromosome 1 and 9. In chromosome 1, C was the major allele with -1.93 and T were the minor allele with 0.00 effects, and in chromosome 9, G was major allele with -0.58 and A was minor allele with -0.14 effects. Identified alleles for grain mold resistance were reported in accessions SC309, SC213, SC833, SC971, and SC1047.