Molecular phylogeny and origin of allopolyploid StH geonomic group in genus elymus

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Wheatgrass genus Elymus is within the same group as wheat, barley and rye. Grasses within the genus Elymus 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, genetic diversity, taxonomy, and speciation in plants. All wheatgrasses are made up of at least two different sets of chromosomes with most species having 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). Some previous studies seem to favor the hypothesis of a multiple origin, but did not provide strong support. We will test whether the StH genome group has multiple origins. If so, we will look at whether we can identify which StH species comes from which Pseudoroegneria (St) and wild barley (H) species using DNA data. Elymus species abundantly occur in Asia and North America. The genetic relationship of Eurasian and North American species is not clear. We shall examine the genetic relationships between Eurasian and North American species. Only eight Elymus species are native to South America. They do not have any obvious connections to Elymus species in other areas. The most probable connection would be with North America or New Zealand. We will examine whether such connections exist.      The outcome of this study will provide significant new knowledge on the genetic relationships of Elymus. The understanding of genetic relationships of Elymus species within and between geographic regions using molecular approaches is of great value and importance for the effective conservation and utilization of the genetic resources in the genus.