Origin And Evolution Of Allopolyploid Wheatgrass Elymus Fibrosus (Schrenk) Tzvelev (Poaceae: Triticeae) Reveals The Effect Of Its Origination On Genetic Diversity

The tribe Triticeae includes not only the world's most economically important cereal crops and forage grasses,but also troublesome weeds distributed all over the world.Within this tribe,three quarters of the species are polyploids.Elymus L.as delimited by L?ve is the only largest genus with exclusively allopolyploids including approximately 150 species.It suggest that allopolyploids Elymus fibrosus with the StH genome was donated by diploid Pseudoroegneria(including St genome)and diploid Hordeum L.(H genome),natural hybridization by heterologous polyploidization has become the StH genome in allopolyploid E.fibrosus.Understanding and studying the origin and evolution of E.fibrosus will be of great significance to the development of polyploid system in wheat.This experiment using low copy RPB2 nuclear gene(the second largest subunit of RNA polymerase II)and chloroplast region trnL-F(spacer between the tRNA Leu(UAA)gene and the tRNA-Phe(GAA)gene)to analyze the allopolyploid E.fibrosus system evolutionary relationships.In this study,ten accessions of E.fibrosus and 19 species with StH genomic and diploid species in tribe Triticeae were analyzed.Chloroplast trnL-F sequence data showed that Pseudoroegneria(including StH genomes)was the maternal donor of E.fibrosus.RPB2 sequence confirmed the presence of StH genome in E.fibrosus,in the phylogeny of RPB2 shows that in St clade,all from E.fibrosus sequence and the sequence from E.canadensis,E.confusus,E.trachycamulus,E.transbaicalensis and E.wawawaiensis were group together,in H clade,all sequences of E.fibrosus except the one from accession PI406448 were placed together,show that St and H chromosomes are more likely to come from a single gene pool.The single origin of E.fibrosus may be one of the reasons why the genetic diversity of E.fibrosus is lower than that of E.caninus,E.alaskanus and E.trachycaulus,which have similar ecological preferences and breeding systems.The convergent evolution of St and H chromosome groups in RPB2 sequence may occur in the evolution history of this allogeneic tetraploid.The results of this study reveal the complex evolutionary history of the E.fibrosus.