RESUMEN
Epichloë endophytes are widely distributed mutualists of cool-season grasses and can protect their hosts against biotic and abiotic stresses. Previous studies have shown that Epichloë endophytes are specific to their grass hosts in tall Festuca and Lolium species. However, no systematic analysis exists of host specificity of asexual Epichloë endophytes and Chinese Elymus species. We analyzed the phylogenetic relationships between Chinese Elymus species and their diploid donor Hordeum species, using their corresponding Epichloë endophyte sequences. We found that 1) the maternal donor of the Chinese Elymus species was the Chinese Pseudoroegneria (St genome) or Hordeum (H genome); and 2) Chinese Hordeum species probably contained two species of Epichloë endophytes. One Epichloë endophyte was also present in a North American Elymus species. The other Epichloë endophyte was found in a Chinese Elymus species. Our results indicate that Epichloë endophytes isolated from Elymus species did not show grass-host specificity. 3) Plant hybridization could probably transform endophyte-free plants (E-) to endophyte-infected plants (E+). Based on our data, we formulate hypotheses about which Epichloë endophytes were spread via plant hybridization.