Molecular Biology and Evolution, doi:10.1093/molbev/msn167
Population Based Re-sequencing Reveals that the Flowering Time Adaptation of Cultivated Barley Originated East of the Fertile Crescent
Huw Jones et al.
Gene re-sequencing and association analysis present new opportunities to study the evolution of adaptive traits in crop plants. Here we apply these tools to an extensive set of barley accessions to identify a component of the molecular basis of the flowering time adaptation, a trait critical to plant survival. Using an association-based study to relate variation in flowering time to sequence-based polymorphisms in the Ppd-H1 gene, we identify a causative polymorphism (SNP48) that accounts for the observed variation in barley flowering time. This polymorphism also shows latitude-dependent geographical distribution, consistent with the expected clinal variation in phenotype with the non-responsive form predominating in the north. Networks, genealogies and phylogenetic trees drawn for the Ppd-H1 haplotypes reveal population structure both in wild barley and in domesticated barley landraces. The spatial distribution of these population groups indicates that phylogeographical analysis of European landraces can provide information relevant to the Neolithic spread of barley cultivation, and also has implications for the origins of domesticated barley, including those with the non-responsive ppd-H1 phenotype. Haplotypes containing the non-responsive version of SNP48 are present in wild barley accessions, indicating that the non-responsive phenotype of European landraces originated in wild barley. The wild accessions whose non-responsive haplotypes are most closely similar to those of landraces are found in Iran, within a region suggested as an area for domestication of barley east of the Fertile Crescent but which has previously been thought to have contributed relatively little to the diversity of European cultivars.