New Insights into the Genomic Structure of Avena L.: Comparison of the Divergence of A-Genome and One C-Genome Oat Species.

We used next-generation sequencing analysis of the 3'-part of 18S rDNA, ITS1, and a 5'-part of the 5.8S rDNA region to understand genetic variation among seven diploid A-genome Avena species. We used 4-49 accessions per species that represented the As genome ( A. atlantica , A. hirtula , and wiestii ), Ac genome ( A.   canariensis ), Ad genome ( A. damascena ), Al genome ( A. longiglumis ), and Ap genome ( A. prostrata ). We also took into our analysis one C-genome species, A. clauda , which previously was found to be related to A-genome species. The sequences of 169 accessions revealed 156 haplotypes of which seven haplotypes were shared by two to five species. We found 16 ribotypes that consisted of a unique sequence with a characteristic pattern of single nucleotide polymorphisms and deletions. The number of ribotypes per species varied from one in A. longiglumis to four in A. wiestii . Although most ribotypes were species-specific, we found two ribotypes shared by three species (one for A. damascena , A. hirtula , and A. wiestii , and the second for A. longiglumis , A. atlantica , and A. wiestii ), and a third ribotype shared between A. atlantica and A. wiestii . A characteristic feature of the A. clauda ribotype, a diploid C-genome species, is that two different families of ribotypes have been found in this species. Some of these ribotypes are characteristic of Cc-genome species, whereas others are closely related to As-genome ribotypes. This means that A. clauda can be a hybrid between As- and C-genome oats.