Abstract
Grain mold is one of the most devasting diseases in sorghum [ Sorghum bicolor L. (Moench)] that affects the endosperm and deteriorates the pericarp tissue, reducing the quality of the grain. Today, sorghum breeding programs have a limited number of sources of resistance for the development of resistant cultivars. Therefore, the USDA-Agriculture Research Service, National Plant Germplasm System Sudan core collection was assessed to identify new sources of grain mold resistance based on seed emergence and deterioration. A total of 246 accessions were evaluated for two years and a subset of 46 accessions with grain mold resistance were subsequently evaluated for two additional years together with 11 breeding resistant lines from the sorghum association panel. The analysis identified 39 grain mold resistance accessions including seven that showed both high seedling emergence (> 82%) and low seed deterioration (< 2.15). Phylogenetic analysis revealed that five accessions (PI 570382, PI 570776, PI 570330, PI 570702, and PI 570348) that clustered distantly from reference sets and showed both high seedling emergence and low seed deterioration can be classified as new resistance sources. Genome-wide association analysis using 147,069 SNPs identified two genomic regions in chromosome 2 and 3 associated with seedling emergence rate and seed deterioration, respectively. The analysis of both genomic regions found two genes of interest associated with phenylpropanoid metabolic process and phosphorylase kinase. These Sudanese grain mold resistance accessions provide new genetically diverse germplasm for breeding programs and insights in the defense resistance responses.