Studies On Molecular Phylogeny Of Hexaploid Species Of Elymus And Roegneria In Triticeae

The Triticeae is a very important goup in Poaceae, which not only includes some important cereal crops, but also cmparises many forage grasses with high values in economy and ecology. The Elymus L. and Roegneria C. Koch are two important perennial genera in Triticeae, which also include many excellent cultivated forage grasses and the special gene pool for genetic breeding and improvement of crops and forages. However, there is a controversy in circumscription of related species and genera and phylogenetic raltionships between these two genera, which is also a hotpot for grass taxomomists. Although, there had been reported many studies about phylogenetic relationships and species circumscription in tetraploid species with StH and StY genome constitution, there is few studies inferred to hexaploid species with the large variation in morphology and taxonomy controversy.A total of26hexaploid species from Elymus and Roegneria, as well as the related tetraploid and diploid species were widely collected from worldwide. The molecular marker including SSR and AFLP, sequence of ITS, trnL-F and low copy gene DMC1were applied for their molecular phylogeny, which could reveal the relationships among the hexaploid species, disscuss the relationships among the St, H, Y genome and detect the related differentiation. The main results were as follows:1. A total of230SSR and EST-SSR markers from5different genera were used to study the transferability to species with St, H, Y genome. Among the230SSR markers,163(70.87%) marker could generate the clear bands, which showed a high transferability for the selective markers. The EST-SSR marker (87.6%) showed a higher transferability than genomic SSR (49.5%), the genomic SSR (86%) also showed a higher polymorphism than EST-SSR (79.8%). The results of cluster showed a related relationship with the genome consititution of the species, the species with same or similar genome could be groups together.2. A total of80materials including47hexaploid species from Elymus and Roegneria were selected to study the phylogenetic relationships using the27high transferability SSR markers. The Dice genetic similarities ranged from0.286-0.981with mean of0.599. Among the hexaploid species, the GS coefficients ranged from0.479-0.981. A high level of genetic diversity had been revealed among the materials. The results of cluster showed that the species with same or similar genome could be grouped together. Then, three different variation types had also been revealed among the species with StHY genome, which also was consistent to the morphology.3. A total of80materials including47hexaploid species from Elymus and Roegneria were also selected to study the phylogenetic relationship using AFLP markers. The Dice genetic similarities ranged from0.215-0.964with mean of0.605. Among the hexaploid species, a total of199bands with94.5%polymorphism were also generated, the GS coefficients ranged from0.391-0.982with an average of0.626. A high level of genetic diversityand genetic divergence had also been revealed among the hexaploid species. The results of AFLP waere agree with the SSR. The AFLP showed a higher analysis efficiency than SSR, which also showed a high related with SSR markers (r=0.734, p=0.024).4. The ITS sequence from43species including26hexploid species from Elymus and Roegneria were used to study the phylogenetic relationships among these materials. A total of40ITS sequences were selected for26hexaploid species. It showed an incomplete converted evolution and St bias pattern of ITS sequence among the hexaploid species. The related far relationship was revealed between St and H genome. The genome differentiation of StHY species was detected and maybe related with the different complex evolution and speciation pattern.5. The chloroplast trnL-F sequence from50species with St. H. Y genome were used to study the phylogenetic relationships among the materials. The results showed that the St genome from Pseudoroegneria was the female parent for all the hexaploid species of Elymus and Roegneria. Then, a significant genome differentiation had alao been revealed, which also indicated that different species with St genome involved inthe speciation of hexaploid species.6. The sequences of low-copy gene DMC1from40speices with St, H, Y genome were applied for elaborating the phylogenetic relationships among the materials. The results showed that a total of61sequences were gained for26hexaploid species, which included25St-copy,20Y-copy,16H-copy. A significant differentiation of St, H, Y genome were also detected, of which H-copy sequences showed the largest variation. Then, the sequences of St and H-copy from hexaploid speices showed a lower variation than relative sequences in diploid speices, which showed that a few donor species from Pseudoroegneria and Hordeum might be involved the formation of hexaploid species. The low-copy nuclear gene also demonstrated the divergence among the species with different genome constitution, such as the different types of hexaploid species with StHY.