Phylogenetic analysis of questionable tetraploid species in Roegneria and Pseudoroegneria (Poaceae: Triticeae) inferred from a gene encoding plastid acety1-CoA carboxylase

To evaluate the phylogenetic relationships of questionable tetraploid species Roegneria alashanica Keng, Roegneria magnicaespes (D.F. Cui) L.B. Cai, Roegneria elytrigioides C. Yen et J.L. Yang, Roegneria grandis Keng and Pseudoroegneria geniculata (Trin.) Á. Löve, the single copy sequences of the plastid acetyl-CoA carboxylase gene (Acc1) were analyzed among the five species and the related diploid and tetraploid species. The results indicated that: (a) R. alashanica contained one set of modified St genome which was closely related to the E^e genome, and the other set of genome was closely related to the P genome; (b) R. magnicaespes contained one set of St genome, the other set of genome might be closely related to the P genome. There are close affinities between R. magnicaespes and R. alashanica; (c) R. elytrigioides contained two sets of St genomes, and it is reasonable to be treated as Pseudoreogneria elytrigioides (C. Yen et J.L. Yang) B.R. Lu; (d) the genome of R. grandis should be designed as St^gY. The St^g genome was a differentiated form of the St genome in Pseudoroegneria and was homoeologous with the Y genome in Roegneria; (e) the genomic constitution of P. geniculata was similar to that of R. magnicaespes and R. alashanica and distinctly related to P. geniculata ssp. scythica (E^eSt). They should be treated as different species in different genera; and (f) the Y genome was possibly originated from the St genome, and was sister to the St, E^e, E^b and W genomes.     

Phylogenetic analysis of the species with awnless lemma in Roegneria (Poaceae,Triticeae) based on single copy of nuclear gene DMC1

To investigate the phylogenetic relationships among species with awnless lemmas in Roegneria and their related diploid genera, the possible genomic constitution and genome donor of species with awnless lemmas in Roegneria, phylogenetic analyses of disrupted meiotic cDNA (DMC1) sequences were investigated in this study. The results showed that: (1) Roegneria alashanica-1 grouped with the Y-type sequences and Roegneria alashanica-2 grouped with the St-type sequences, confirming that Roegneria alashanica has the StY genomes. (2) Roegneria grandis-1 grouped with the Y-type sequences and Roegneria grandis-2 grouped with the St-type sequences, confirming that Roegneria grandis has the St^gY genomes, where the St genome from R. grandis is different from the St genome but is homologous with the Y genome. (3) Two Roegneria elytrigioides sequences grouped with the St-type sequences, confirming that Roegneria elytrigioides has the St₁St₂ genomes and should therefore be classified as Pseudoroegneria elytrigioides. (4) We prefer the suggestion that the Y genome is closely related to the St genome, however, the data do not certify that the St and Y genomes have the same origin.     

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.     

大鹅观草与蛇河披碱草属间杂种的细胞遗传学研究

为探讨大鹅观草(Roegneria grandis,2n=4x=28)的染色体组组成,为其正确的分类处理提供细胞学依据。该研究通过人工远缘杂交,成功获得3株大鹅观草与蛇河披碱草(Elymus wawawaiensis,2n=4x=28)属间杂种F1植株。杂种植株形态介于两亲本之间,不育。亲本及杂种经I2-IK溶液染色后进行花粉育性检测,结果显示Roegneria grandis和Elymus wawawaiensis的花粉可育,育性高达94.6%和90.5%;杂种F1不育。花粉母细胞减数分裂中期I染色体配对结果显示,亲本花粉母细胞配对正常,均形成14个二价体,以环状二价体为主,Roegneria grandis有频率很低(0.04/细胞)的单价体出现;杂种F1平均每个花粉母细胞形成6.46个二价体,变化范围为5~8;在观察的83个花粉母细胞中,有35.2%的花粉母细胞形成了7个二价体,形成6个二价体的细胞占42.59%,较少细胞形成8个二价体;平均每个细胞形成14.66个单价体,变化范围为10~18;平均每细胞观察到0.14个三价体;杂种花粉母细胞染色体构型为14.66 I+6.46 II+0.14 III;平均每细胞交叉数为9.83,C值为0.35。结果表明:(1)R.grandis与Elymus wawawaiensis有一组染色体组同源的St染色体组,另外一组染色体组不是St或者H染色体组,Roegneria grandis的染色体组组成不是St Stg;(2)较低频率的三价体(平均0.14个/细胞),可能是由于R.grandis的St和Y染色体组间具有一定的同源性,也可能是染色体易位等原因导致,对于Y染色体组的起源还需深入地研究;(3)在不同地理来源的披碱草属和鹅观草属物种中St染色体组同源性不同,R.grandis与来自于北美的Elymus lanceolatus与E.wawawaiensis的St染色体组较与分布于亚洲的E.sibiricus和E.caninus的St染色体组同源性反而更高,其原因还需要进一步地研究。     

Cytogenetic analyses inKengyilia laxiflora (Poaceae, Triticeae)

Kengyilia laxiflora (2n = 42) was cytogenetically studied with testersK. hirsuta (2n = 42, PPStStYY) andRoegneria kamoji (2n = 42, HHStStYY). Our data suggested thatK. laxiflora may possess a modified P genome, the P¹. Its St and Y genomes may also contain some structural changes and are more closely related to the St and Y genomes ofK. hirsuta than to those ofR. kamoji. Kengyilia laxiflora is reproductively separated from bothK. hirsuta andR. kamoji. These results indicated thatK. laxiflora is a good species in the genusKengyilia.     

Hybridisation,genomic constitution and generic delimitation inElymus s. l. (Poaceae: Triticeae)

Intergeneric crosses were made between representatives of the genomically-defined generaElymus, Agropyron, Elytrigia, Pseudoroegneria, andThinopyrum. The genomic constitution ofElytrigia repens, the type species ofElytrigia, is shown to be SSH, a genomic combination otherwise found only inElymus. The S genome ofPseudoroegneria has almost always a dominant influence on the morphology of the taxa of which it is a component.Wang (1989) showed that the J genome inThinopyrum and the S genome have considerable homoeology, with a mean c-value of 0.35 in diploid SJ hybrids. A genetic coherence from S to SJ^e, J^e, J^eJ^b, and J^b can be expected, agreeing with the continuous morphologic variation pattern observed. Because of the absence of morphological discontinuities between the taxa,Pseudoroegneria (S),Elymus (SH, SY, sometimes with additional genomes),Elytrigia (SSH, SSHX), andThinopyrum (SJ, SJJ, J) are best treated as a single genus,Elymus, following the generic concept ofMelderis in Flora Europaea and Flora of Turkey. The basic genomic constituents ofElymus will then be the S and/or J genomes.Agropyron, with diploids, tetraploids, and hexaploids based on the P genome is morphologically distinct from other genera inTriticeae. In a few species ofElymus andPseudoroegneria, a P genome is an additional constituent. In these cases the P genome has a negligible morphological influence. Therefore, it seems reasonable to maintainAgropyron as a separate genus.     

The genome constitution ofRoegneria grandis (Poaceae, Triticeae)

Roegneria grandis was hybridized withR. ciliaris var.japonensis (2n = 28, SSYY),Elymus caninus (2n = 28, SSHH), andPseudoroegneria spicata (2n = 28, SSSS). Chromosome pairing was studied in parents and hybrids. It is concluded from this study that: (i)R. grandis is an allotetraploid species and contains the basic genomes S and Y: (ii) a certain degree of homoeology exists between the S and Y genomes of the species studied.     

Biosystematic study ofRoegneria tenuispica, R. ciliaris andR. pendulina (Poaceae:Triticeae)

Morphological and cytological studies of three tetraploidRoegneria species,R. tenuispica, R. pendulina andR. ciliaris, and their artificial hybrids were carried out.Roegneria tenuispica was morphologically similar toR. pendulina. The general appearance of the interspecific hybrids was intermediate between the parents. The hybrids showed comparatively high chromosome pairing at meiosis, but were completely or almost completely sterile. The results indicate that the three independent species share two basic genomes (S_tY) and thatR. tenuispica is more closely related toR. pendulina than toR. ciliaris. The genomes ofR. tenuispica could be designated as S _t ^t Y^t.     

应用RAPD特异标记分析拟鹅观草属部分物种的基因组组成

选用小麦族中8个基本基因组(E、H、I、P、St、W、Ns、R)的特异RAPD引物进行PCR扩增检测,分析Pseudoroegneriagracillima、P.kosaninii、Roegneriaalashanica和R.magnicaespes这4个四倍体物种的基因组组成。结果表明:P.gracillima、P.kosaninii、R.alashanica和R.magnicaespes中除了含有St或经修饰的St基因组外,都不含E、H、I、P、W、Ns和R基因组,由此推断P.gracillima和P.kosaninii至少含有一个St或经修饰的St基因组,另一个基因组是否为Y基因组,需要进一步研究证实。结合前人细胞遗传学研究的结果,推断R.alashanica和R.magnicaespes为同源四倍体或部分同源四倍体,其基因组组成为StStStSt或St1St1St2St2。因此,结合外部形态特征以及前人细胞遗传学、分子标记研究和核型分析的结果,推断R.alashanica和R.magnicaespes与P.elytrigioides一样,也可能是在中国分布的四倍体拟鹅观草属物种,为系统整理和研究国产拟鹅观草属物种及其地理分布提供了DNA分子水平上的资料。     

Distinct origin of the Y and St genome in Elymus species: evidence from the analysis of a large sample of St genome species using two nuclear genes

Background

Previous cytological and single copy nuclear genes data suggested the St and Y genome in the StY-genomic Elymus species originated from different donors: the St from a diploid species in Pseudoroegneria and the Y from an unknown diploid species, which are now extinct or undiscovered. However, ITS data suggested that the Y and St genome shared the same progenitor although rather few St genome species were studied. In a recent analysis of many samples of St genome species Pseudoroegneria spicata (Pursh) À. Löve suggested that one accession of P. spicata species was the most likely donor of the Y genome. The present study tested whether intraspecific variation during sampling could affect the outcome of analyses to determining the origin of Y genome in allotetraploid StY species. We also explored the evolutionary dynamics of these species.

Methodology/Principal Findings

Two single copy nuclear genes, the second largest subunit of RNA polymerase II (RPB2) and the translation elongation factor G (EF-G) sequences from 58 accessions of Pseudoroegneria and Elymus species, together with those from Hordeum (H), Agropyron (P), Australopyrum (W), Lophopyrum (E^e), Thinopyrum (E^a), Thinopyrum (E^b), and Dasypyrum (V) were analyzed using maximum parsimony, maximum likelihood and Bayesian methods. Sequence comparisons among all these genomes revealed that the St and Y genomes are relatively dissimilar. Extensive sequence variations have been detected not only between the sequences from St and Y genome, but also among the sequences from diploid St genome species. Phylogenetic analyses separated the Y sequences from the St sequences.

Conclusions/Significance

Our results confirmed that St and Y genome in Elymus species have originated from different donors, and demonstrated that intraspecific variation does not affect the identification of genome origin in polyploids. Moreover, sequence data showed evidence to support the suggestion of the genome convergent evolution in allopolyploid StY genome species.     

垂穗披碱草与达乌里披碱草基因组细胞遗传学比较

采用顺序FISH-GISH技术,12个重复序列探针,包括9个三核苷酸简单重复序列、2个卫星DNA重复序列pSc119.2和pAs1以及5S rDNA,通过重复序列的物理定位对达乌里披碱草和垂穗披碱草基因组中部分重复序列的分布特征进行了比较分析,为进一步研究垂穗披碱草和达乌里披碱草的物种形成及演化提供新的分子细胞遗传学证据。结果表明:(1)所有的序列在这2个物种的染色体上都能产生可检测的杂交信号,且在2个物种中(AAC)_(10)、(ACT)_(10)、(CAT)_(10)都表现为共分布,(AAG)_(10)与(AGG)_(10)表现为近似共分布;2个物种的H基因组除5S rDNA序列外,其他序列都产生强烈且丰富的杂交位点,St与Y基因组不同重复序列探针的荧光位点数目有所差别,表现为5S rDNA、pSc119.2、(AAC)_(10)、(CAT)_(10)、(ACT)_(10)、(CAC)_(10)探针的信号位点较少或无信号,其余的探针信号位点稍多。(2)达乌里披碱草的第2对染色体上具有(AAC)_(10)、(CAT)_(10)、(ACT)_(10)的杂交位点、第6对染色体上具有(CAC)_(10)的杂交位点,而在垂穗披碱草的St基因组中未观察到上述序列杂交位点;达乌里披碱草St基因组仅有第4对染色体的端部具有pSc119.2杂交位点,而在垂穗披碱草St基因组中的pSc119.2杂交位点位于第5对染色体长臂的间隔区;相对于达乌里披碱草,垂穗披碱草St和Y基因组染色体含有更多的重复序列杂交位点。(3)达乌里披碱草的H/Y基因组间易位在不同材料间是稳定存在的,达乌里披碱草基因组相对稳定,不同材料间H基因组重复序列杂交信号多态性高于St和Y基因组;垂穗披碱草基因组的变异较大,不同材料间St和Y基因组重复序列杂交信号多态性高于H基因组。研究认为,垂穗披碱草和达乌里披碱草的H基因组均起源于布顿大麦,St基因组可能起源于不同的拟鹅观草属物种;与达乌里披碱草相比垂穗披碱草St与Y基因组可能具有更高的染色体结构变异性,而垂穗披碱草St与Y基因组变异较大的原因可能是与同区域分布的含StY基因组的物种发生了种间渗透杂交。     

Phylogenetic relationships of species in <Emphasis Type="Italic">Pseudoroegneria</Emphasis> (Poaceae: Triticeae) and related genera inferred from nuclear rDNA ITS (internal transcribed spacer) sequences

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 and E ^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.     

The origin of the H, St, W, and Y genomes in allotetraploid species of Elymus L. and Stenostachys Turcz. (Poaceae: Triticeae)

Based on sequences from two single-copy nuclear genes (DMC1 and EF-G), four plastid genes (rbcL, rpoA, matK, and ndhF), and one mitochondrial gene (coxII), we investigate the origin of the H, St, W, and Y genomes in four allotetraploid species of Elymus and two allotetraploid species of Stenostachys. Despite significant incongruence between the two nuclear genes and between the nuclear and organelle data partitions, individual and combined analyses of the data partitions unequivocally show that the St and H genomes of the tetraploid American species of Elymus are derived from Pseudoroegneria and Hordeum, respectively, with Pseudoroegneria serving as the female parent, and that the H and W genomes of Stenostachys are derived from Hordeum and Australopyrum, respectively, with Hordeum serving as the female parent. The analyses equally clearly demonstrate that the St genome of the tetraploid Asiatic Elymus species is derived from Pseudoroegneria, with the latter serving as the female parent, but the relationship of the Y genome is less clear. Individual analyses of the nuclear genes provide conflicting results, but combined analysis of all data suggests a sister group relationship to Heteranthelium, albeit without any jackknife support.     

Maternal origin,genome constitution and evolutionary relationships of polyploid <Emphasis Type="Italic">Elymus</Emphasis> species and <Emphasis Type="Italic">Hordelymus europaeus</Emphasis>

The trnS/psbC region of chloroplast DNA (cpDNA) was sequenced for 18 Elymus polyploid species, Hordelymus europaeus and their putative diploid ancestors. The objective was to determine the maternal origin and evolutionary relationships of these polyploid taxa. Phylogenetic analysis showed that Elymus and Pseudoroegneria species formed a highly supported monophyletic group (100 % bootstrap values), suggesting that Pseudoroegneria is the maternal genome donor to polyploid Elymus species studied here. The phylogenetic tree based on cpDNA sequence data indicates that E. submuticus contains a St-genome. Taking into consideration of our previously published RPB2 data, we can conclude that hexaploid E. submuticus contains at least one copy of St and Y genomes. Our Neighor-joining analysis of cpDNA data put Psathyrostachys juncea, Hordeum bogdanii and Hordelymus europaeus into one group, suggesting a close relationship among them.     

Molecular evolution and diversity of dimeric alpha-amylase inhibitor gene in Kengyilia species (Triticeae: Poaceae)

Kengyilia Yen et J. L. Yang is a group of allohexaploid species with StYP genomic constitutions in the wheat tribe. To investigate the evolution and diversity of dimeric alpha-amylase inhibitor genes in the Kengyilia, forty-five homoeologous DAAI gene sequences were isolated from sampled Kengyilia species and analyzed together with those of its close relatives. These results suggested that (1) Kengyilia species from Central Asia and the Qinghai–Tibetan Plateau had different origins from those of the geographically differentiated P genome; (2) the St and P genomes of Kengyilia were donated by Pseudoroegneria and Agropyron, respectively, and the Y genome had an independent origin and showed an affinity with the St genome; (3) purifying selection dominated the DAAI gene members and the St-DAAI gene was evolving at faster rate than the P- and Y-DAAI genes in Kengyilia; and (4) natural selection was the main factor on the codon usage pattern of the DAAI gene in Kengyilia.     

Phylogenetic relationships between Leymus (Poaceae,Triticeae) and related diploid Triticeae species based on isozyme and genome-specific random amplified polymorphic DNA (RAPD) markers

Abstract

To investigate the phylogenetic relationships between Leymus and related diploid species of the Triticeae tribe, the esterase isozyme (EST), superoxide dismutase (SOD) isozymes, and genome-specific random amplified polymorphic DNA (RAPD) markers were used to analyze for 14 Leymus species, together with two Psathyrostachys species (Ns), three Pseudoroegneria species (St), two Hordeum species (H), Lophopyrum elongatum (E^e), Australopyrum retrofractum (W), and Agropyron cristatum (P). The data were used to construct dendrograms by means of UPGMA in the NTSYS-pc computer program. The results suggested that (1) isozyme analysis can be used in the systematic studies of these perennial Triticeae; (2) there is a close relationship between Leymus, Psathyrostachys juncea, three Pseudoroegneria species, and Lophopyrum elongatum; (3) the Ns genome-specific RAPD marker was present in all 14 polyploid species of Leymus, while the E^e and P genome-specific RAPD markers were absent in 14 polyploid species of Leymus; the St, W and H genome-specific RAPD markers were present in some species of Leymus; (4) Leymus species have multiple origins, and different Leymus species derived their genomes from different donors.     

A cointegrate of the bacteriophage P1 genome and the conjugative R plasmid R100

Restriction cleavage analysis identified a P1CmSmSuTc plasmid isolated by Mise and Arber (1976) (Virology 69, 191–205) as a cointegrate between bacteriophage P1 and the R plasmid R100. Cointegration occurred by reciprocal recombination between the IS1 element of P1 and IS1b of R100. It involved neither gain nor loss of genetic material, so that the cointegrate carries three IS1 elements in the same orientation. The cointegrate propagates with relatively high stability as plasmid in Escherichia coli host bacteria. It displays the Tra⁺ functions of R100, incompatibility FII of R100, and incompatibility Y of P1, Res⁺ (P1), Mod⁺ (P1) functions of P1 and P1 immunity. Production of P1 phage particles is inducible as for wild type P1. However, because of the large genome size of 180 kb, progeny phage particles contain only a fraction (about 100 kb) of the cointegrate genome. Because of cyclic permutation all genome regions are equally represented in a population of the phage particles of an induced lysate. Occasionally, reciprocal recombination between IS1 elements allows the restoration of the P1 genome. These segregants are found as plaque formers at a rate of about 1 per 300 phage particles in induced lysates.     

Phylogenetic relationships among the species of <Emphasis Type="Italic">Elymus</Emphasis> sensu lato in Triticeae (Poaceae) based on nuclear rDNA ITS sequences

The genus Elymus L. sensu lato includes Roegneria, Elymus, Hystrix, Sitanion and Kengyilia, and they are very important group in the tribe Triticeae. However, the phylogenetic relationships and taxonomic status of them are still in dispute. The ITS sequences were obtained and analyzed for their phylogenetic relationships by using Maximum Parsimony (MP) and Bayesian Inference (BI) methods. The main results were as follows: (1) Most species in Roegneria, Elymus and Sitanion were clustered in the St clade with diploid St genome species, and it was difficult to distinguish the species in Roegneria and Elymus; (2) The polyploid species with St genomes in the St clade were divided into three groups, which suggests that there exists differentiation of St genome in polyploids; (3) Most species of Kengyilia have only P-type of clone and clustered with diploid Agropyron species, which may suggest that Kengyilia is a valid genus; (4) Hy. patula, the type species of Hystrix was clustered with species of Elymus, while Hy. duthiei ssp. duthiei, Hy. duthiei ssp. longearistata, Hy. coreana and Hy. komarovii were grouped with diploid Psathyrostachys species. It indicated that Hy. patula is distinct related to other Hystrix species, and it is reasonable to treat Hystrix patula as Elymus hystrix and other species in Hystrix should be transferred to Leymus; (5) The “clones bias” in ITS sequences are widespread in the allopolyploid species. The article is published in the original.     

Phylogenetic relationships among Leymus and related diploid genera (Triticeae: Poaceae) based on chloroplast trnQ–rps16 sequences

To investigate the phylogenetic relationships among Leymus and related diploid genera, the genome donor of Leymus, and the evolutionary history of polyploid Leymus species, chloroplast trnQ–rps16 sequences were analyzed for 36 accessions of Leymus representing 25 species, together with 11 diploid taxa from six monogenomic genera. The phylogenetic analyses (Neighbor‐Joining and MJ network) supported three major clades (Ns, St and Xm). Sequence diversity and genealogical analysis suggested that 1) Leymus species from the same areas or neighboring geographic regions are closely related; 2) most of the Eurasian Leymus species are closely related to Psathyrostachys: P. juncea might serve as the Ns genome donor of polyploid Eurasian Leymus species; 3) the Xm genome may originate from ancestral lineages of Pseudoroegneria (St), Lophopyrum (E^e), Australopyrum (W) and Agropyron (P); 4) the trnQ–rps16 sequences of Leymus are evolutionarily distinct, and may clarify parental lineages and phylogenetic relationships in Leymus.     

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

The Pseudoroegneria species are perennial grasses in the Triticeae tribe, whose St genome has been linked to several important polyploid species. Due to frequent hybridization and complex genetic mechanism, the relationships within Pseudoroegneria, and within the Triticeae have been heavily disputed. Using the chloroplast rbcL gene we estimated the nucleotide diversity of 8 Pseudoroegneria species. We also examined the phylogenetic relationships within Pseudoroegneria and of Pseudoroegneria within the Triticeae. The estimates of nucleotide diversity indicated that Pseudoroegneria tauri and Pseudoroegneria spicata species had the highest diversity, while Pseudoroegneria gracillima had the lowest diversity. The phylogenetic analysis of Pseudoroegneria placed all P. spicata species into a clade separate from the other Pseudoroegneria species, while the relationship of the other Pseudoroegneria species could not be determined. Due to the groupings of Pseudoroegneria with the polyploid Elymus, our results strongly supported Pseudoroegneria as the maternal genome donor to Elymus. There was also weak support that P. spicata may be the maternal donor to the StH Elymus species.