| The tribe Triticeae is one of the important groups in Poaceae,which includes about 350-450 species distributed in all over the world,especially in the warm temperate zones of north hemisphere.Elytrigia Desv.,a polyploid perennial genus in Triticeae(Poaceae)includes 40 species in the world,distributing in the subtropical and warm temperate countries of both hemispheres.Some species in this genus are important genetic reservoir for wheat improvement which are the excellent perennial forages with resistance to cold,drought,salinity,and various diseases.The definition of Elytrigia and its precise taxonomic status are still under discussion today.In 1810,Elytrigia was erected as the type species by Desvaux with Elytrigia repens(L.)Nevski.Morphologically,the species in Elytrigia sensu lato are characterized as branched creeping rhizomes and caespitose,long anthers,lanceolate to linear glumes,lanceolate lemma,single spikelet per node and cross-pollinating grasses previously in traditional Agropyron Gaertner.The chromosome numbers of the species within this genus ranges from 2n=2x=14 to 2n=12x=84.Genome which is constituted of traditional Elytrigia,contains E,St,ESt,EStP,NsXmStH.With the development of research methods,the genomic definition of Elytrigia sensu stricta is much narrower than traditional definitions,and only includes all the polyploidy taxa that have Ee,Eb and St genome only.So,according to the genomic system of classification proposed by Love(1984)and Dewey(1984),there are several questions need to be resolved,such as the origin,definition of the genus,precise taxonomic rank sand relationships among the species in the genus.The present study systematically evaluated the genetic diversity of Elytrigia on cytology,molecular phylogenetic reconstruction,network analysis and biochemistry.Besides,we also investigated the biosystematic relationships among species and evolution level in this genus.The main results showed as follows:1.The karyotype analyses of twelve species in Elytrigia were carried out.Their karyotype formulas are as follows:Elytrigia bessarabica,2n=2x=14=14m;Et.libanotica,2n=2x=14=2M+8m(2sat)+4sm;Et.gracillima,2n=2x=14=2M+10m+2sm;Et.caespitosa,2n=4x=28=2M+24m+2sm;Et.nodusa,2n=4x=28=2M+22m+4sm;Et.scirpea,2n=4x:=28=2M+22m+4sm(2sat);Et.scythica,2n=4x=28=22m+6sm(2sat);Et.varnensis,2n=4x=28=28m;Et.elongatiformis,2n=6x=42=42m;Et.intermedia,2n=6x=42=32m+10sm(2sat);Et.pycnantha,2n=6x=42=40m+2sm;Et.smithii,2n=8x=56=34m+22sm(4sat).The karyotype type of diploid species is 1A,and the polyploidy species are 1B or 2B.These results suggest that great karyotype variations(ploidy,karyotype formulas,numbers and locations of satellite chromosomes)exist among these species or even populations in same species.The karyotypes of 8 species among material analyzed were reported for the first time.Meanwhile,the karyotype evolution and the systamatic implications from cytogenetic data were discussed in the present study.According to Stebbins’ theory of the karyotypic evolution as well as the method of coding of cladistics,were analyzed,and the evolutional levels of the 12 species were also affirmed.The results indicate that Et.bessarabica is relatively most primitive species while Et.smithii is relatively most advanced species in the 12 species analyzed.2.The trnL-F sequences of 24 Elytrigia(Eb,Ee,EeEeSt,EbEeSt,EeSt,StSt,StH,EStP)species were analyzed together with those of two species of Agropyron(P),two species of Australopyrum(w),two species of Eremopyrum(F),two species of Hordeum(H),two species of Psathyrostachys(Ns),one species of Pseudoroegneria(St)by using the Bayesian Inference(BI)and Median-joining(MJ)network approaches.The results indicate that:(1)the species of Elytrigia are clustered into one clade,and their sequences are homology and closely related;(2)polyploid species in Elytrigia have E,St and other maternal donor;(3)species of Eremopyrum,Agropyron and Australopyrum are clustered into one clade,and their sequences are closely related and homologous;(4)E genome diploid species in Elytrigia served as the maternal donor of the E genome for Et.caespitosa ssp.nodosa(PI547344),Et.farcta,Et.pontica,Et.pycnantha,Et.scirpea and Et.scythica;(5)the maternal genome of one species or one genome group could be original from different species.3.Based on nrITS sequences,phylogenetic analysis was performed for 23 species within Elytrigia,together with 12 diploid taxa from 12 monogenomic genera.The main results were:(1)species with E,St and ESt genomes within Elytrigia were closely related;(2)diploid species with St genomes were differentiated;(3)E genome in ESt genomes species derived from Et.elongata;(4)the diploid species Et.elongata showed differentiation;(5)the genomic constitutions of Et.pachynera was StH and this species should be removed to Elymus;(6)the relationships of St,P and F genome are very close.4.Phylogenetic analysis based on the disrupted meiotic cDNA1(DMC1)sequences were constructed for 24 species of Elytrigia species,two species of Elymus species(StH),together with 10 diploid species.The results indicate that:(1)the genome StStH was identified from Et.repens,the type species of Elytrigia;this species should be put into the genus Elymus;(2)As a proportion of Elytrigia Desv.,some species containing E gnomes are closely related with Lophopyrum A.Love,some containing St are closely related with Pseudoroegneria(Nevski)A.Love,some containing ESt gnomes are closely related with Trichopyrum A.Love,and some containing EStP gnomes are closely related with Psammopyrum A.Love.All of these relationships are in the line with the classification regulations according to the constituent of genomes;(3)the E and St genome of ESt species may be come from Lophopyrum and Pseudoroegneria;(4)according to the genomic system of classification proposed,Et.pachynera should be transferred to Elymus,Et.pycnantha should be transferred to Psammopyrum and Et.pontica should be transferred to Trichopyrum;(5)Ee and Eb genomes are closely related to each other,but there are still differences existed;(6)the E genomes in polyploidy species were differentiated.5.The polymorphism of gliadin and glutelin in 24 species in Elytrigia were studied by using acid polyacrylamide gel electrophoresis(A-PAGE)and SDS polyacrylamide gel electrophoresis(SDS-PAGE).Different electrophoresis patterns of gliadin and glutelin were appeared in all of the 24 tested materials,and in total 83 gliadin bands and 53 glutelin bands were extracted respectively which indicate 100%polymorphism.The results show that:(1)there are rich gliadin and glutelin genetic polymorphism in Elytrigia,and the gliadin and glutelin patterns show significant variation among the materials;(2)the gliadin and glutelin patterns can be used as a fingerprint in identifying different species from Elytrigia;(3)the relationships among species in Elytrigia base on gliadin and glutelin data are basically the same as the results of cytology and molecular biology data.The gliadin and glutelin patterns data may be used to investigate genetic variation and biosystematic relationships among species in Elytrigia. |
PDF Full Text Request