Phylogenetic relationships of Elymus L. and related genera (Poaceae) based on the nuclear ribosomal internal transcribed spacer sequences

To help in the clarification of the taxonomic status of Elymus L. and related genera Agropyron Gaertn., Leymus Hochst., Hordelymus (Jess.) Harz, and Brachypodium P.Beauv., the sequence diversity in the internal transcribed spacer (ITS) region of nuclear ribosomal DNA was studied. ITS data of 64 Triticeae accessions including 40 Elymus, 12 Agropyron, 7 Leymus, and 4 Hordelymus, and 1 Brachypodium as an out-group were analysed. The molecular diversity statistics indicated that the most diverse genus is Elymus among the studied genera. The constructed phylogenetic tree by the maximum parsimony method revealed that one specimen of Elymus, E. pycnanthus (Godr.) Melderis, clustered with species of Agropyron. Molecular diversity statistics also indicated that E. pycnanthus is distantly related to other species of Elymus, but is closer to Agropyron species. The finding of strong affinity of Elymus to the species of Leymus and Agropyron supports the view that the taxonomy of Elymus is further complicated by the role of hybridisation among different ancestral genera.