Phylogenetic relationships of species in Pseudoroegneria (Poaceae: Triticeae) and related genera inferred from nuclear rDNA ITS (internal transcribed spacer) sequences

Abstract

To evaluate the phylogenetic relationships of species in Pseudoroegneria and related genera, the nuclear ribosomal internal transcribed spacer (ITS) sequences were analyzed for eighteen Pseudoroegneria (St), two Elytrigia (E e St), two Douglasdeweya (StP), three Lophopyrum (E e andE b ), three Agropyron (P), two Hordeum (H), two Australopyrum (W) and two Psathyrostachys (Ns) accessions. The main results were: (i) Pseudoroegneria gracillima, P. stipifolia, P. cognata and P. strigosa (2x) were in one clade, while P. libanotica, P. tauri and P. spicata (2x) were in the other clade, indicating there are the differentiations of St genome among diploid Pseudoroegneria species; (ii) P. geniculata ssp. scythica, P. geniculata ssp. pruinifera, Elytriga caespitosa and Et. caespitosa ssp. nodosa formed the E e St clade with 6-bp indel in ITS1 regions; and (iii) Douglasdeweya wangii, D. deweyi, Agropyron cristatum and A. puberulum comprised the P clade. It is unreasonable to treat P. geniculata ssp. scythica and P. geniculata ssp. pruinifera as the subspecies of P. geniculata, and they should be transferred to a new genus Trichopyrum, which consists of species with E e St genomes. It is also suggested that one of the diploid donor of D. wangii and D. deweyi is derived from Agropyron species, and it is reasonable to treat tetraploid species with StP genomes into Douglasdeweya.

Phylogenetic analysis of the genus Pseudoroegneria and the Triticeae tribe using the rbcL gene

“…These grasses are palatable to animals and are drought and salt tolerant. This makes them highly desirable for plant breeders (Dewey, 1984;Lӧve, 1984;Yu et al, 2008).…”

“…A cytological study by Wang et al (1995), found that the St genomes of different Pseudoroegneria species have become highly diverged. This indicates that there may be more than one form of the St genome within the Pseudoroegneria genus, and new genomic designation may be necessary (Yu et al, 2008). Further studies, including those on the granule-bound starch synthase I (GBSSI) gene (Mason-Gamer, 2001;MasonGamer et al, 2010), the RPB2 genes (Sun et al, 2008;, ITS of nuclear rDNA (Yu et al, 2008), the EF-G genes (Sun & Komatsuda, 2010; phosphoenolpyruvate carboxylase (Pep-C) (Mason-Gamer et al, 2010) and ß-amylase (Mason-Gamer et al, 2010), have found two distinct clades within the St genome of Pseudoroegneria.…”

“…This indicates that there may be more than one form of the St genome within the Pseudoroegneria genus, and new genomic designation may be necessary (Yu et al, 2008). Further studies, including those on the granule-bound starch synthase I (GBSSI) gene (Mason-Gamer, 2001;MasonGamer et al, 2010), the RPB2 genes (Sun et al, 2008;, ITS of nuclear rDNA (Yu et al, 2008), the EF-G genes (Sun & Komatsuda, 2010; phosphoenolpyruvate carboxylase (Pep-C) (Mason-Gamer et al, 2010) and ß-amylase (Mason-Gamer et al, 2010), have found two distinct clades within the St genome of Pseudoroegneria. In the GBSSI, RPB2, EF-G, and ß-amylase gene phylogenies, P. libanotica and P. tauri have very similar sequences and are sufficiently different from the other diploid Pseudoroegneria so as to form a separate clade (Mason-Gamer et al, 2010;Sun et al, 2008;Sun & Komatsuda, 2010;.…”

Identification of EeSt-genome species in Pseudoroegneria and Elytrigia (Poaceae: Triticeae) by using SCAR markers from ITS sequences

“…Based on chloroplast and nuclear DNA data, Mason-Gamer (2004) found a complex pattern of reticulate evolution, introgression, and intertribal gene capture in E. repens. Yu et al (2008) (Liu and Wang, 1993a,b;Xu and Conner, 1994;Zhang et al, 1996;Refoufi et al, 2001;Ellneskog-Staam et al, 2003;Yu et al, 2010). SCAR primers generated right fragments in these E e St-genome taxa, but not in St-genome and E-genome species.…”

“…Therefore, detecting E e St genomes in polyploid species using genome analysis or based on morphology similarity is inadequate, and the taxonomic treatment of E e St-genome species remains disordered. Previous internal transcribed spacer (ITS) analysis showed that a 6-base pair (bp) indel (TTTTCA) exits in E e St-genome species, but not in species with St or E (E e and E b ) genomes (Li et al, 2004;Yu et al, 2008). This provides insight into E e St-genome diagnosis using sequence characterized amplified region (SCAR) markers on a molecular level.…”