Molecular Phylogenetic And Cytological Studies On Elymus L. Sensu Lato (Triticeae: Poaceae)

Triticeae Dumortier is a very important group in the tribe Poaceae which includes three of the most important cereal crops,i.e.,wheat,barley,and rye,as well as many economically valuable forage grasses.The genus Elyrnus L.sensu lato delimited by L(o|¨)ve is an important perennial genus of Triticeae Dumortier(Poaceae),and contains approximately 150 perennial and exclusively polyploid species occurring from the Arcic and temperate to subtropicalall regions.It includes the traditional species of Roegneria, Hystrix,Sitanion and Kengyilia.Many species are free herbages,and some species have characters of resistance to disease,insect resistance and stress tolerance,which are precious germplasm resources in crop forage breeding.The species in Elymus s.1.are allopolyploids ranging from tetraploids,hexaploids to octaploids with different genomic constitutions.Because of the large numbers and wide distribution,the definitions,precise taxonomic ranks of the genus and the phylogenetic relationships among species have been under discussion.Cytological studies suggest that five basic genomes,namely,the St,Y,H, P,and W in various combinations constitute Elymus species.St was/ecognized as the maternal donor of the species in Elymus s.1.,however,this result need further confirmation. The Y genome was also an important foundamental genome in Elymus s.1.Because of the unknown donor of the Y genome the extensive investigations should be carried out.In this study,data from molecular systematical and cytogenetic analyses have been used to systematically evaluate the phylogenetic relationships of the genus and to deduce the evolution history of the polyploid species.The main results are as follows:1.The ITS sequences were analyzed from 75 species by using Maximum Parsimony(MP) and Bayesian Inference(BI) methods.The main results were:(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 Psctthyrostachys 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.2.The plasid trnL-F sequences were analyzed from 48 species.The results indicated that: (1) the maternal donor of Elymus s.1.species is not always from Pseudoroegneria.The P genome serves as the maternal donor of K.melanthera and K.thoroldiana,while the Ns genome is the maternal donor of Hy.duthiei ssp.duthiei and Hy.duthiei ssp.longearistata; (2) the MP tree from trnL-F reveals the close relationships among P,W and St genomes, while the H and Ns are distinctly related to them;(3) K.melanthera and K.thoroldiana were clustered with diploid Agropyron species,which indicated the close relationships among them.Hy.patula was clustered in the St clade,while Hy.duthiei ssp.duthiei and Hy. duthiei ssp.longearistata were grouped in the Ns clade.It indicated that the genomic constitution of Hy.patula is different from Hy.duthiei ssp.duthiei and Hy.duthiei ssp. longearistata,which supported the ITS results from this study;(4) the five diploid species. with St genome didn't form the monophyletic clades,which suggested the differentiation of the diploid species;(5) The polyploid species with St genomes were not clustered in one clade,which suggests that there exists differentiation of St genome in polyploids;(6) the species distributed in Asia may originated from the diploid species of Pseudoroegneria from Eurasia,while the North America Elymus species may originated from North America Pseudoroegneria species.Some species may have a multiple origin and experienced recurrent hybridization between species with different genomes.3.The chloroplast trnL-F sequences of 14 Kengyilia species and its related diploid species were analyzed by using Maximum Parsimony(MP) and Bayesian Inference(BI) methods. The species in Kengyilia were clustered into two different clades.K.melanthera,K.mutica and K.thoroldiana grouped with diploid Agropyron(P) species,while the rest species clustered in St+E^e+E^b clade,which indicated that Agropyron(P) is the likely maternal genome donor to K.melanthera,K.mutica and K.thoroldiana,while the maternal donor to K.batalinii,K.nana,K.kokonorica,K.kaschgarica,K.hirsuta,K.alataviea,K.gobicola, K.zhaosuensis,K.rigidula,K.longiglumis and K.grandiglumis was St or Y genome. 4.The single copy sequences of the plastid acetyl-CoA carboxylase gene(Accl) of R. alashanica,R.magnicaespes,R.elytrigioides,R.grandis and P.geniculata and their related species were analyzed.The results indicated that:(1) R.alashanica contains one set of modified St genome which is closely related to the E^e genome,and the other set of genome was closely related to the P and H genomes;(2) R.magnicaespes contains one set of St genome,the other set of genome may be closely related to the P and H genomes;(3) R.elytrigioides contains two sets of St genomes,and it is reasonable to be treated as P. elytrigioides;(4) the genome of R.grandis should be designed as St^gY.The St^g genome is a differentiated form of the St genome in Pseudoroegneria and is homoeologous with the Y genome in Roegneria;(5) P.geniculata contains one set of St genome,the other set of genome may be closely related to the P,H and W genomes.The genomic constitution of P. geniculata is distinctly related to P.geniculata ssp.scythica(E^eSt),and they should be treated as different species in different genera;(6) the Y genome was possibly originated from the St genome,and was closely related to E^e,E^b,St and W genomes;and(7) R. alashanica,R.magnicaespes,P.geniculata were closer to each other than to R. elytrigioides.R.grandis is distinctly related to the four species.5.The interspecific and intergeneric hybrids among diploid Pseudoroegneria species and Elymus s.1.species with different genomes were analyzed.The fertility and chromosome paring behavior in meiosis of the parents and their hybrids F₁ were investigated.The results indicated that:(1) the St genome in P.libanotica and P.tauri which come from Iran maybe different from that of P.spicata in North America;(2) differentiation of the St genome was found in allopolyploid species with StY,StH and StYW genome combinations;(3) a certain degree of homoeology has been observed between St and Y genomes.St genome is closely related to Y genome and distinct from H genome.