Phylogenetic relationship and origin of allopolyploid StH geonomic species in genus elymus

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Wheatgrass genus Elymus is within the same group as wheat, barley and rye, and 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 by 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 is 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. Eight South American native Elymus species 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. On the basis of morphological traits, the StH species in Elymus were classified into seven sections. We will use DNA sequence data to test whether the species with similar morphology are genetically related to each other.     The outcome of this study will provide a phylogenetic framework for studying the evolutionary processes that have contributed to the morphological complexity of the Elymus. Such findings also have agronomic relevance because of the many agriculturally useful species in Elymus. Given their potential importance in germplasm improvement, understanding of the origin and relationships of these species are of both practical and theoretical interest.