Origin and evolution of tetraploid species in genus elymus

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Wheatgrass genus Elymus is within the same group as wheat, barley and rye. Grasses within this genus have adapted to various climates and habitats, making them valuable genetic resources for cereal and forage breeding as well as an excellent group for research in evolution, taxonomy, and speciation. All wheatgrasses are made up of at least two different sets of chromosomes with most species having the StY and StH chromosome combination. There are about 50 species with StH combination. The St genome comes from ancestor species in genus Pseudoroegneria and H from wild barley. One debate on this group has been whether different StH species arose by an ancient cross between the one pair of parents, a Pseudoroegneria species and a wild barley and then differentiated into a number of species (single origin), or different StH species arose by crosses between different pairs of the parents at different times and places (multiple origins). We will test whether the St and H genomes in Elymus are of multiple origins. It has been hypothesized that allopolyploid StY species may have an origin from autopolyploid (StStStSt) and the same genome differentiated gradually within the polyploid species resulting in today's StY genome allotetraploid Elymus. Our rpb2 data did not support the same origin of St and Y genome in StY species. Phylogenetic analysis of the StY species usig other genes will test whether StY species are allopolyploid origin. My study will be designed to test whether the St and H haplomes in StH species are of multiple origins, and characterize differences between cytogenetically distinct StH and StY species. Lastly, I shall test if StY genome species is allo- or autopolyploid origin and examine genetic relationships of the Y genome to other genomes in Triticeae.