Problems of crosses between various oat species are considered with regard to establishing their taxonomic positions and genomic compositions of individual species. The evolution of the genus and approaches to the search for the diploid and tetraploid ancestor of the hexaploid species are considered. Use of wild oat species in breeding is demonstrated. The results of studies of the gene pool of wild oat species are presented. These studies were performed at the Vavilov All-Russian Plant Breeding Institute with the purpose of solving problems of phylogeny and practical breeding.