Genomic Resources for Complex Trait Dissection and Molecular Breeding in Sorghum

Sorghum is a critical staple food crop of semi-arid regions, a major source of feed and forage worldwide, and an emerging bioenergy crop. Given its relatively compact genome and diverse carbon allocation patterns (i.e. starch, sugars, and structural carbohydrates), it is also an excellent model system for the dissection of complex traits relevant to the Saccharinae (e.g. maize, sugarcane, and Miscanthus). Here we present new genomic resources in sorghum that facilitate the use of diverse germplasm in genetic mapping and molecular breeding. We describe a genome-wide map of single-nucleotide polymorphisms (SNPs), currently covering >1,400 accessions genotyped at >370,000 SNPs, that permits high-resolution genome-wide association studies (GWAS) and marker-assisted selection. Based on this SNP map, we present a general strategy for high-powered GWAS in sorghum, which takes into account the complex genetic history and population structure of this widely-adapted crop and its wild relatives. Finally, we summarize progress on the development of nested association mapping (NAM) populations for genetic dissection of biomass traits in high-yielding, photoperiod-sensitive bioenergy type sorghum.