内生真菌与人工草地禾草之间的互利共生关系已经被大量的实验证据所证实。近年来的研究表明，内生真菌在天然禾草中也广泛存在，并且有比人工禾草中更高的种类多样性，但内生真菌对天然禾草宿主的影响存在明显的不确定性。结合前期的工作，我们推测：内生真菌-天然禾草之间相互作用的不确定性除与共生体所处的环境有关外，与共生体双方特别是内生真菌的种类密切相关。羽茅是内蒙古中东部草原常见的伴生种，同时也是有性和无性型内生真菌的天然宿主，本研究以来自两个不同地理种群的、不同基因型的羽茅为材料，首先通过人工转接的方式，构建宿主植物基因型完全相同的、分别感染有性和无性内生真菌的植物种群，在研究不同种类内生真菌对宿主生长和代谢影响的基础上探讨不同种类内生真菌对宿主及其所在群落中其它植物及土壤微生物等的影响。本研究不仅有助于阐明内生真菌在决定共生体相互作用性质方面所起的作用，而且有助于预测染菌植物所在群落的发展和演替方向。

It is well known that asexual endophytes are usually mutualistic with their host grasses such as tall fescue and perennial ryegrass. Recently, endophytic fungi are reported to be widely distributed in native grasses. Unlike most agronomic grasses that are infected by a single epichlo? species, natural populations are usually comprised of plants harboring multiple endophyte species. Studies involving native grasses are relatively scarce and results range from antagonistic to mutualistic. We suggest that this variation is at least partly resulted from the difference of epichlo? species. Achnatherum sibiricum is a perennial, sparse bunch grass and a constant companion species native to the east-central Inner Mongolia Steppe. In the previous study, we found that A. sibiricum is highly infected by epichlo? endophytes. Up to now, A. inebrians and A. robustum, belonging to the same genus with A. sibiricum, are also found to be infected by Neotyphodium endophytes and both are notorious for the narcotic properties to livestock ascribed to endophyte infection. In contrast to A. inebrians and A. robustum, A. sibiricum has no obvious herbivore deterrence according to local records and our own observations. Particularly, A. sibiricum harbors both asexual Neotyphodium and their Epichlo? sexual ancestors, which can be transmitted vertically or horizontally, depending on environmental conditions. In our previous study, A. sibiricum has been sampled from two geographical populations. In each population, at least three genotypes have been obtained. Grass tillers, with identical genotype, have been re-infected with Neotyphodium gansuense and Epichlo? amarillans, separately, by artificial inoculation. The purpose of this study is to compare the effect of different endophyte species on the host grass, and further on the dominant non-host species, microbial community and the associated grassland community. Our object is not only to study the contribution of endophyte species variation to endophyte-grass interactions, but also to provide some basic insights into the development and succession of the endophyte associated grassland.