Application of molecular markers to assess genetic relationships among accessions of wild oat, Avena sterilis

The Avena sterilis collection in the National Small Grains Collection (NSGC) is an invaluable source of genetic variation to be exploited by oat breeding programs. Prior knowledge of the structure and distribution of genetic variation within the A. sterilis collection would be useful to efficiently screen the collection for valuable traits. To determine genetic structure within a subset of the collection, restriction fragment length polymorphisms were analyzed in a stratified sample of 173 accessions originating in eight countries of Africa and Southwest Asia. Of the 48 probes used for this study 43 detected polymorphism among accessions. The average number of RFLP patterns per probe ranged from 2.9 among Ethiopian accessions to 3.7 among those from Iran. Genetic variation, as measured by genetic distances and polymorphic indexes, was highest in Iran and lowest in Ethiopia. The probability of drawing a genotype from Iran or Iraq that is not present in the more western regions was high, indicating large genetic divergence of the Iran-Iraq accessions from the other regional collections surveyed. Cluster analysis of genetic distances and probabilities of unique genotypes clearly differentiated the eastern region (Iran and Iraq) from the western region (Algeria, Ethiopia, Israel, Lebanon, Morocco, and Syria). The western region could be further subdivided into two clusters, an African cluster (Algeria, Ethiopia, and Morocco) and a southwestern Asia cluster (Israel, Lebanon, and Syria). Genetic distances were generally related to but not proportional to geographical distances.