The [SNP's] That Shake the Barley

Scientists at the University of Minnesota and UC Irvine recently published their analysis of 803 regional domesticated varieties (landraces) and 277 wild strains of barley. The study finds that barley---a self-pollinating diploid cereal grain with a long history of human cultivation, ideal for genetic studies---cannot be traced to a single origin of domestication. Comparing single-nucleotide polymorphisms, Poets et al confirm that barley has been domesticated multiple times in human history, but over the course of extensive trade in this crop, regional cultivars have admixed with sympatric wild strains. Recent introgression is ruled out, so the ultimate conclusion falls to ancient gene flow. Each domestic cultivar exhibits admixture from multiple wild types, but with the greatest contributions being from geographically proximate wild barleys; domestic barley in the Levant shares more SNP's with Levantine wild barley, domestic barley in Central Asia shares more SNP's with Central Asian wild barley, and so on. Most fascinatingly, certain regions of the genome seem more prone to fixing this gene flow, raising the possibility that alleles gained from local wild barley are somehow adaptive. As the world's barley-growing regions are quite diverse, this makes sense and gives some insight to the nature of early human agriculture.

Fig. 1 - Negative correlation between admixture and geographic distance between cultivar and wild strain

Source article published in Genome Biology