The effect of tropical sorghum conversion and inbred development on genome diversity as revealed by high-resolution genotyping

Abstract

Graphical genotypes have been generated for a set of sorghum [Sorghum bicolor (L.) Moench] germplasm, which includes selected public inbreds, germplasm from the world collection, and ancestral lines central to the early breeding efforts of sorghum. We have focused our present examination on sorghum chromosome SBI-06, which encodes ma1 and dw2, two genes critical to sorghum improvement dating to the original introduction of tropical sorghums into the United States. Utilizing the pedigree relationship between sorghum cultivars, the patterns of genetic variation were detailed within segmental chromosomal blocks of SBI-06. Segmental genomic blocks were traced back through multiple generations of a pedigree, often back to founder tropical accessions. The graphical genotypes reveal genomic signatures of historical breeding decisions, especially evidence of directional selection during the conversion of tropical accessions to temperate adaptation. This information is central to our efforts to understand those crop improvement processes that have shaped the genomic diversity of elite sorghum cultivars.