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

麦草属与小麦、大麦和黑麦属于同一类群。羊草属禾草适应了各种气候和生境，是谷物和饲草育种的宝贵遗传资源，也是研究植物进化、遗传多样性、分类学和物种形成的优秀类群。所有的小麦草都由至少两组不同的染色体组成，大多数品种都有StY和StH染色体组合。有StH组合的物种约有50种。其中St基因组来自于原属Pseudoroegneria， H基因组来自于野生大麦。关于这一群体的一个争论是，不同的StH物种是由一对亲本、一种Pseudoroegneria物种和一种野生大麦之间的古代杂交产生的，然后分化成多个物种（单一起源），还是不同的StH物种是由不同时间和地点的不同对亲本杂交产生的（多重起源）。以前的一些研究似乎支持多起源假说，但没有提供强有力的支持。我们将测试StH基因组组是否有多个起源。如果是这样，我们将研究我们是否可以利用DNA数据确定哪个H种来自哪个假芽孢菌（St）和野生大麦(H)种。在亚洲和北美有丰富的羊草种类。欧亚种和北美种的遗传关系尚不清楚。我们将研究欧亚和北美物种之间的遗传关系。只有8种羊草原产于南美洲。它们与其他地区的羊草类没有明显的联系。最有可能的联系是北美或新西兰。我们将研究这种联系是否存在。本研究结果将为进一步了解羊草属植物的遗传关系提供重要的新知识。利用分子方法研究地理区域内和地理区域间的羊草种亲缘关系，对有效保护和利用羊草属遗传资源具有重要意义。

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.