show Abstracthide AbstractThe genus Avena includes all wild and cultivated species of oat: an important and nutritious food crop. We characterized genetic diversity of more than 9000 wild and cultivated hexaploid oat accessions using single nucleotide polymorphisms derived from genotyping by sequencing. We found strong population structure within the wild species A. sterilis, including five sub-populations related to region of origin. The cultivated red oat, A. byzantina, also constituted a distinct population. The distinctness of these populations may support hypotheses of multiple polyploid origins and/or sexual barriers caused by differential chromosome structure.