Molecular phylogeny of RNA polymerase II gene reveals the relationships of tetraploid species with St genome (Triticeae: Poaceae)

To evaluate phylogeny of tetraploid with St genome, phylogenetic analyses of RNA polymerase II (RPB2), a member of the nuclear gene family encoding the second largest subunit, were performed. Our results showed that: (1) Roegneria magnicaespes and Roegneria alashanica are related to Pseudoroegneria. (2) Roegneria elytrigioides has StStStSt genomes and should therefore be classified as Pseudoroegneria elytrigioides. (3) Pseudoroegneria tauri and Pseudoroegneria deweyi which have StStPP genomes should be transferred to Douglasdeweya and be renamed as Douglasdeweya wangii and Douglasdeweya deweyi, respectively. (4) Pseudoroegneria geniculata ssp. scythica is related to Pseudoroegneria and Lophyrum, and hence should be identified as a species of Trichopyrum. (5) Pseudoroegneria libanotica might be a parental donor for Elytrigia caespitosa rather than Elytrigia caespitosa ssp. nodosa. It is unreasonable to recognize El. caespitosa ssp. nodosa as a subspecies of El. caespitosa. (6) Interspecific and intergeneric variations are detected in St genome of these tetraploid species.