Genome-Wide Association Studies of Grain Traits in Sorghum.

Cereal grains account for two-thirds of human caloric consumption and are the main food source for livestock.  Locating genes in sorghum [Sorghum bicolor (L.) Moench] associated with grain yield and quality will be useful for marker-assisted breeding and allow for the use of genomic tools to understand and manipulate these traits.  To identify the genetic variation underlying grain yield and quality, a genome-wide association study (GWAS) on a diverse panel of approximately 400 accessions, all of which have been genotyped-by-sequencing for over 265,000 single nucleotide polymorphisms (SNPs), will be used to locate regions and candidate genes throughout the sorghum genome associated with grain size, number per panicle, thousand grain weight, starch quantity and variation, crude protein, fat, and acid detergent fiber.  Near-infrared reflectance (NIR) spectroscopy will be employed to determine grain compositional characteristics.  Preliminary data show significant starch variation among cultivars in the panel which includes all five subpopulations as well as the ten intermediates. Several a priori starch candidates identified in previous studies and sorghum orthologs of maize genes within the starch biosynthesis pathway provide target locations for further study across the genome.