Molecular Genotyping of Historical Barley Landraces Reveals Novel Candidate Regions for Local Adaption

Barley landraces from Northern Europe form genetically distinct latitudinal groups, suggesting that adaption plays an important role in the geographical distribution of genetic diversity. Here, we investigate how Northern European barley landraces relate to landraces from other parts of Europe and whether candidate genes for climate adaption can be identified. For this purpose, 27 barley landraces, available as century-old seed specimens, were genotyped with a 384 single nucleotide polymorphism (SNP) assay. Landraces from the Nordic countries formed a genetically distinct group relative to landraces from Central and Southern Europe. Polymorphic positions in the flowering time genes HvCO1, HvFT1, Ppd-H1, and VRN1-H1 were genotyped. The previously known allele distribution of Ppd-H1 with the responsive allele present in the South and the nonresponsive allele in the North was confirmed. The other three genes were more variable in Central and Southern Europe compared to the North and neither of the flowering time genes showed any geographically correlated variation within the Nordic countries. Allelic frequencies from the 384 SNP set were correlated with climatic variables. This allowed us to identify five SNPs putatively associated with length of growth season, and two SNPs putatively associated with precipitation. The results show how historical crop specimens can be used to study how genetic variation has been geographically distributed and the genetics of adaption.