Nucleotide divergence and genetic relationships of Pseudoroegneria species

Nucleotide variation in 8 diploid Pseudoroegneria species was characterized using two single copy nuclear genes, the second largest subunit of RNA polymerase II (RPB2) and the translation elongation factor G (EF-G), and one chloroplast TrnD/T intergenic region. Among the Pseudoroegneria species studied, the estimates of nucleotide diversity (π) ranged from 0.04577 (RPB2) and 0.00183 (TrnD/T) for Pseudoroegneria tauri to 0.10667 (RPB2), 0.06174 (EF-G) and 0.03743 (TrnD/T) for Pseudoroegneria spicata. The highest nucleotide diversity of the RPB2 data set was found for P. spicata among the taxa analyzed. Our phylogenetic analyses separated the accessions of P. spicata into several groups, with 7 accessions of P. spicata forming a highly supported subclade (BS = 100%, PP = 1.00). The phylogenetic analysis also suggests that P. spicata, Pseudoroegneria gracillima and Pseudoroegneria stipifolia have a closer relationship than the other species within Pseudoroegneria. Pseudoroegneria libanotica and P. tauri were also found to exhibit a high level of sequence homology, however, only nuclear gene data (RPB2 and EF-G) clearly indicated the differentiation between the P. libanotica + P. tauri group with other St genome species.