Molecular and cytological evidences for the natural wheatgrass hybrids occurrence and origin in west China
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Keywords:
Elymus
Triticeae
Leymus
Tribe
Agropyron
To estimate the phylogenetic relationships between Hystrix and its related genera (Poaceae: Triticeae), the sequences of the single-copy nuclear gene Pgk1 were analyzed for five Hystrix taxa, together with three Pseudoroegneria (St) species, two Hordeum (H) species, two Psathyrostachys (Ns) species, four Elymus (StH) species, five Leymus (NsXm) species, Thinopyrum bessarabicum (E(b)), and Lophopyrum elongatum (E(e)). Sequence analysis indicated that an 81bp Stowaway insertion occurred in the Pgk1 sequences of L. arenarius and Psa. juncea, and a 29 bp Copia insertion occurred in the Pgk1 sequences of Hy. duthiei, Hy. duthiei ssp. longearistata and L. akmolinensis. Phylogenetic analysis indicated that: (1) Hy. patula was closely related to Pseudoroegneria, Hordeum, and Elymus; (2) Hy. duthiei, Hy. duthiei ssp. longearistata, Hy. coreana, and Hy. komarovii were closely related to Psathyrostachys and Leymus. Based on these results, it is reasonable to transfer Hy. patula from Hystrix to Elymus, and to combine Hy. duthiei, Hy. duthiei ssp. longearistata, Hy. coreana, and Hy. komarovii into Leymus.
Triticeae
Leymus
Elymus
Hystrix
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To help in the clarification of the taxonomic status of Elymus L. and related genera Agropyron Gaertn., Leymus Hochst., Hordelymus (Jess.) Harz, and Brachypodium P.Beauv., the sequence diversity in the internal transcribed spacer (ITS) region of nuclear ribosomal DNA was studied. ITS data of 64 Triticeae accessions including 40 Elymus, 12 Agropyron, 7 Leymus, and 4 Hordelymus, and 1 Brachypodium as an out-group were analysed. The molecular diversity statistics indicated that the most diverse genus is Elymus among the studied genera. The constructed phylogenetic tree by the maximum parsimony method revealed that one specimen of Elymus, E. pycnanthus (Godr.) Melderis, clustered with species of Agropyron. Molecular diversity statistics also indicated that E. pycnanthus is distantly related to other species of Elymus, but is closer to Agropyron species. The finding of strong affinity of Elymus to the species of Leymus and Agropyron supports the view that the taxonomy of Elymus is further complicated by the role of hybridisation among different ancestral genera.
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Leymus
Agropyron
Triticeae
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Abstract The taxonomic status of Hystrix and phylogenetic relationships among Hystrix and its related genera of Pseudoroegneria (St), Hordeum (H), Psathyrostachys (Ns), Elymus (StH), Leymus (NsXm), Thinopyrum bessarabicum (E b ) and Lophopyrum elongatum (E e ) were estimated from sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. The type species of Hystrix , H. patula , clustered with species of Pseudoroegneria , Hordeum , Elymus , Th. bessarabicum and Lo. elongatum , while H. duthiei ssp. duthiei , H. duthiei ssp. longearistata , H. coreana and H. komarovii were grouped with Psathyrostachys and Leymus species. The results indicate that: (i) H. patula is distantly related to other species of Hystrix , but is closely related to Elymus species; (ii) H. duthiei ssp. duthiei , H. duthiei ssp. longearistata , H. coreana and H. komarovii have a close affinity with Psathyrostachys and Leymus species, and H. komarovii might contain the NsXm genome of Leymus ; and (iii) the St, H and Ns genomes in Hystrix originate from Pseudoroegneria , Hordeum and Psathyrostachys , respectively, while the Xm in Hystrix and Leymus has a complex relationship with the E or St genomes. According to the genomic system of classification in Tiritceae, it is reasonable to treat Hystrix patula as Elymus hystrix L, and the other species of Hystrix as species of a section of Leymus , Leymus Sect. Hystrix .
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Hystrix
Elymus
Triticeae
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Abstract Leymus is a genus in the Triticeae tribe, Poaceae. The taxa of this genus are allopolyploid species which possess the Ns and Xm genomes. According to cytological, cytogenetic and molecular genetic analyses, some species of Hystrix and Elymus ought to be transferred to this genus. A world revision of the genus Leymus is needed. In this paper we summarize experimental results, provide a key to sections, species and varieties, and list all the taxa we recognize in Leymus with their synonyms. This synopsis is a new taxonomic system to be used for the revision of Leymus .
Leymus
Triticeae
Hystrix
Elymus
Chemotaxonomy
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The taxonomy of the perennial grasses of the Triticeae tribe ( Agropyron, Elymus , et al.) has been in an unsettled state for many years, with Eurasian and North American authorities often using different systems of classification and applying different names to the same species. North Americans have generally relied on the treatment given in A.S. Hitchcock's 1951 Manual of the Grasses of the United States , while realizing that it was seriously outdated. Publication of treatments of the Triticeae in Poaceae URSS by N.N. Tzvelev in 1976 and in Flora Europaea by A. Melderis et al. in 1980 has made it advisable for North Americans to reevaluate their taxonomic traditions with respect to these grasses. Tzvelev's treatment is compatible with biological relationships as determined by chromosome pairing in interspecific and intergeneric hybrids. The perennial genera of the Triticeae recognized by Tzvelev include: 1) Agropyron (restricted to A. cristatum and other crested wheatgrasses), 2) Elymus (self‐fertilizing and caespitose species previously in Elymus and Agropyron ) 3) Leymus (usually cross‐pollinating and often rhizomatous species previously in Elymus ), 4) Elytrigia (usually cross‐pollinating and rhizomatous or caespitose species previously included in Agropyron , with the exception of the crested wheatgrasses), 5) Psathyrostachys (crosspollinating species with brittle rachises and multiple spikelets, including Russian wildrye), and 6) Hordeum (treated in its traditional sense). With a few exceptions, I endorse Tzvelev's treatment because it closely reflects biological and phylogenetic relationships.
Triticeae
Elymus
Agropyron
Leymus
Agropyron cristatum
Polyploid
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Leymus
Triticeae
Elymus
Concerted evolution
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The phylogenetic relationships of 15 taxa from Hystrix and the related genera Leymus (NsXm), Elymus (StH), Pseudoroegneria (St), Hordeum (H), Psathyrostachys (Ns), and Thinopyrum (E) were examined by using the Giemsa C-banded karyotype. The Hy. patula C-banding pattern was similar to those of Elymus species, whereas C-banding patterns of the other Hystrix species were similar to those of Leymus species. The results suggest high genetic diversity within Hystrix, and support treating Hy. patula as E. hystrix L., and transferring Hy. coreana, Hy. duthiei ssp. duthiei and Hy. duthiei ssp. longearistata to the genus Leymus. On comparing C-banding patterns of Elymus species with their diploid ancestors (Pseudoroegneria and Hordeum), there are indications that certain chromosomal re-arrangements had previously occurred in the St and H genomes. Furthermore, a comparison of the C-banding patterns of the Hystrix and Leymus species with the potential diploid progenitors (Psathyrostachys and Thinopyrum) suggests that Hy. coreana and some Leymus species are closely related to the Ns genome of Psathyrostachys, whereas Hy. duthiei ssp. duthiei, Hy. duthiei ssp. longearistata and some of the Leymus species have a close relationship with the E genome. The results suggest a multiple origin of the polyploid genera Hystrix and Leymus.
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Triticeae
Elymus
Polyploid
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The typification and circumscription of some genera allied to Agropyron Gaertn. and Elymus L. are outlined. It is concluded that Agropyron is not a native of Britain; the species formerly included in it, or in Elylrigia Desv. or Roegneria C. Koch, should be treated under Elymus L., and the single British species treated under Elymus should be transferred to Leymus Hochst. New combinations are made for two varieties and three hybrids under Elymus, and for one inter-generic hybrid under x Elyhordeum Mansfeld ex Zizin & Petrova. GENERIC LIMITS The absence of clear-cut generic characters has created much difficulty in the delimitation of the group of genera around Agropyron Gaertn. sensu lato and Elymus L. sensu lato . Recent cytogenetical evidence and analysis of the morphological characters of species belonging to these genera have , however, thrown some light on the inter-relationships of these genera. The results of these investigations have been utilized in a revisio;} of the genera in question (Melderis 1978), and the new combinations were adopted in Flora Europaea (Melderis 1980). The name Agropyron Gaertn., Nov. Comment. Acad. Sci. Imp. Petrop., 14 (1): 539 (1770), has been typified by A. cristatum (L.) Gaertn. This species and its allies seem to be well-isolated , being taxonomically and genetically distinct from the other genera. The species of this genus possess a single genome, which has not been found elsewhere. Some members of Agropyron, such as A . cristatum subsp. pectinatum (Bieb.) Tzvelev and A . desertorum (Fischer ex Link) Schultes, are rare casuals in Britain. Agropyron caninum (L.) Beauv. and its allies have mostly been placed in the genus Agropyron, but are sometimes segregated into Roegneria C. Koch, Linnaea, 21: 413 (1848), of which the type species is R. caucasica C. Koch. They exhibit a close morphological and ecological affinity with Elymus sibiricus L., which is the type of both Elymus L. , Sp. Plo 83 (1753) and Clinelymus (Griseb.) Nevski, Bull. Jard. Bot. Acad. Sci. URSS, 30: 640 (1932), but in the past they were kept in separate genera, mainly on the basis of the spikelet arrangement on the rhachis (solitary in A. caninum and its allies , in pairs or threes in E. sibiricus and its allies). Occasionally, however, A. caninum and some related species bear spikelets in pairs in the lower part of the rhachis. On the other hand, the Asiatic Elymus nutans Griseb. , a close relative of E. sibiricus, occasionally possesses solitary spike lets on the rhachis , causing difficulty in distinguishing it from an Asiatic species of Agropyron (A. schrenkianum (Fisch . & Mey.) Cantargy) related to A. caninum. These facts indicate that the arrangement of spikelets on the rhachis is of limited taxonomic value. The recent cytogenetical investigations also indicate a close relationship between these groups, which have similar genomes in common. Therefore, they should both be placed in the genus Elymus. The genus Elytrigia Desv. , Nouv. Bull. Sci. Soc. Phi/om. Paris, 2: 190 (1810), is often used to include the group of species around the rhizomatous E. repens (L.) Nevski, which is the type species, although more usually they have been placed in Agropyron. Some representatives of the A . repens
Elymus
Agropyron
Leymus
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Typification
Agropyron cristatum
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Hystrix
Triticeae
Leymus
Elymus
Polyploid
Agropyron
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Citations (54)
Abstract Understanding the classification and biosystematics of species in Triticeae Dumort., an economically important tribe in the grass family (Poaceae), is not an easy task, particularly for some perennial species. Does genomic analysis facilitate the understanding of evolutionary relationships of these Triticeae species? We reviewed literature published after 1984 to address questions concerning: (1) genome relationships among the monogenomic diploid species; (2) progenitors of the unknown Y genome in Elymus polyploids, X genome in Thinopyrum intermedium , and Xm genome in Leymus ; and (3) genome constitutions of some perennial Triticeae species that were unknown or misidentified. A majority of publications have substantiated the close affinity of the E b and E e genomes in Th. bessarabicum and Th. elongatum , supporting the use of a common basic genome symbol. The E genome is close to the St genome of Pseudoroegneria and ABD genomes of Triticum / Aegilops complex, providing an explanation for transferring genes from the E to ABD genomes with relative ease. Although the solid proof is still lacking, the W , P , and especially Xp genomes are possible origins for the Y genome of polyploid Elymus . The absence of the E genome and the allopolyploidy nature of tetraploid Leymus species have been unequivocally confirmed by both cytogenetic and molecular studies. However, the donor of the Xm genomes of Leymus was only speculated to be related to the P genome of Agropyron and F genome of Eremopyrum . Intermediate wheatgrass ( Th. intermedium ) has been extensively studied. The presence of the St (as the previously designated X ) genome in Th. intermedium is now unequivocal. Its two more closely related E 1 and E 2 genomes are shown to be older versions of the E genome rather than the current E b and E e genomes. Speciation of Th. intermedium was similar to that of Triticum aestivum , in which the J s /E s (like B ) genomes had the greatest differentiation from the current J ( E b ) genome owning to repetitive sequences of the V genome, whereas its St (like D ) had the least differentiation from the current St genome. Species with unknown or misidentified genomes have been correctly designated, including those with the ESt , StP , StPY , StWY , EStP , HW , StYHW , and NsXm genomes. Some of those species have been transferred to and renamed in appropriate genera.
Triticeae
Leymus
Elymus
Polyploid
Agropyron
Aegilops
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