Phylogenetic Analysis of Leymus (Poaceae: Triticeae) Inferred from Nuclear rDNA ITS Sequences

Abstract

To investigate the phylogenetic relationships of polyploid Leymus (Poaceae: Triticeae), sequences of the nuclear rDNA internal transcribed spacer region (ITS) were analyzed for 34 Leymus accessions representing 25 species, together with three Psathyrostachys species (Ns genome), two Pseudoroegneria (St genome) species, Lophopyrum elongatum (E(e) genome), and Thinopyrum bessarabicum (E(b) genome). The phylogenetic analyses (maximum likelihood and Bayesian inference) supported two major clades, one including 21 Leymus species and three Psathyrostachys species, the other with nine Leymus species and four diploid species. The ITS RNA secondary structure of the Leymus species was compared with that of their putative diploid donor. It is suggested that (1) the species from the same areas or neighboring geographic regions are closely related to each other; (2) L. coreanus, L. duthiei, L. duthiei var. longearistatus, and L. komarovii are closely related to other Leymus species, and it is reasonable to transfer these species from the genus Hystrix to Leymus; (3) the ITS sequences of Leymus are evolutionarily distinct; (4) the different Leymus species and different distribution of a species derived their Ns genome from different Psathyrostachys species; and (5) there is a close relationship among Leymus, Pseudoroegneria, Lophopyrum, and Thinopyrum, but it is difficult to presume that the St, E(e), and E(b) genome may be the Xm genome donor of the Leymus species.

Phylogenetic analysis of Elymus (Poaceae) in western China

“…E. dolichatherus (AY740834, AY740836, and AY740837) from Sichuan Province and E. dolichatherus (KF905169) contained some nrITS copies in clade I, but collections (KF905155, KF905156, KF905167, and KF905172) from the Qinghai-Tibetan plateau were in clade II. Similar results were observed in Leymus based on nrITS sequences (Sha et al, 2008). Their results showed that species from the same areas or neighboring geographic regions were closely related to each other Leymus species.…”

Sequence variation in ITS spacers and 5.8S rDNA and relationship of E, St, P, Ns, Xm, and H genomes in the genera of Agropyron, Elytrigia, Leymus, Pascopyrum, Psathyrostachys, and Hordeum

“…Thus size variations were not extensive among the haplotypes. The narrow range of size variations of the ITS-1 and ITS-2 in our analysis and invariable length of 5.8S rDNA were noted in other studies (Baldwin et al, 1995;Sha et al, 2008). Slightly longer ITS-1 to ITS-2 in E and P genomes was also reported by Baldwin et al (1995) in various species in several plant families.…”

“…In our analysis, the in/del of penta-nucleotide (A/T)GGGG in ITS-1 of E and St genomes makes them slightly longer than ITS-2. Sha et al (2008) also reported similar penta-nucleotide in/del variation among the Leymus species. In their analysis, different accessions within a species showed presence/absence polymorphism of the penta-nucleotide.…”

Phylogenetic relationships between Leymus and related diploid Triticeae species revealed by ISSR markers

“…ITS date showed that L. hybrid, L. triticoides, L. ambiguous, L. salinus, and L. cinereus which distributed in North America were grouped together with some Leymus species from central Asia (Sha et al 2008).RAPD analyzing suggested that the Leymus species from North America were scattered in different groups and clustered with those species from central Asia ). The present study showed that L. ambiguus scattered in subgroup Ia, the two accessions of L. triticoides and L. mollis clustered in subgroup Ib, meanwhile, two accessions of L. cinereus, two accessions of L. salinus, L. hybrid and L. innovatus were relatively grouped together in subgroup Ic.…”

“…Leymus was originally defined as a genomically allopolyploid genus with two distinct subgenomes Ns and Xm. Meiotic pairing data from interspecific and intergeneric hybrids (Dewey 1984;Wang 1994) and molecular studies (Jensen et al 1997;Sha et al 2008) had revealed that the Ns genome of Leymus was originated from Psathyrostachys. Despite decades of intensive efforts in cytogenetic and molecular biology researches, there are still uncertainties regarding the origin of the Xm genome of Leymus.…”