Epichloë endophytes may not only affect the growth and resistances of host grasses, but may also affect soil environment including soil microbes. Can Epichloë endophyte-mediated modification of soil microbes affect the competitive ability of host grasses? In this study, we tested whether Epichloë endophytes and soil microbes alter intraspecific competition between Epichloë endophyte-colonized (EI) and endophyte-free (EF) and interspecific competition between and . The results demonstrated that Epichloë endophyte colonization significantly enhanced the intraspecific competitive ability of and that this beneficial effect was not affected by soil microbes. Under interspecific competition, however, significant interactions between Epichloë endophytes and soil microbes were observed. The effect of Epichloë endophytes on interspecific competitiveness of the host changed from positive to neutral with soil microbe removal. Here higher mycorrhizal colonization rates probably contributed to interspecific competitive advantages of EI over EF . Our result suggests that Epichloë endophytes can influence the competitive ability of the host through plant soil feedbacks from the currently competing plant species.
