Establishment, Characterization, and Analysis of the Sorghum Bioenergy Association Panel: A Resource for Genetic Improvement.

Sorghum [Sorghum bicolor (L.) Moench] is a highly productive genetically diverse C₄ grass with over 3 million hectares in domestic annual production.  Sorghum, which has primarily been harvested for its grain, is increasingly being cultivated for its biomass as a forage and bioenergy feedstock. Forage and bioenergy sorghum require a different ideotype and carbon partitioning profile than the combine height grain sorghum currently in production. To facilitate the genetic improvement of sorghum as a forage and bioenergy feedstock, we characterized an association panel of 345 individuals with 232,303 high quality SNPs. Individuals were chosen based on racial, geographic, and phenotypic diversity.  Population structure and genomic analysis show that this panel is distinct from other established sorghum association panels To show the power of this panel for association mapping, we perform a GWAS on a known trait (pericarp pigmentation) along with more complex agronomic (height and dry weight) and compositional (structural and nonstructural carbohydrates) phenotypes. The GWAS revealed novel loci with candidate genes affecting carbon-partitioning patterns between structural and nonstructural carbohydrates. These results, combined with our characterization of phenotypic and genetic diversity, demonstrate the value of this panel for association genetics and lay the foundation for future sorghum bioenergy development.