Epichloë endophytes of a wild grass promote mycorrhizal colonization of neighbor grasses

A field experiment was performed to study the effect of Epichloë endophytes of the wild forage grass Bromus auleticus on mycorrhizal colonization, seedling emergence and growth parameters in three heterospecific grasses of agronomic interest. Plots with B. auleticus associated with Epichloë (E+) and non-associated (E-) plants were established and 3 y later, seeds of Lolium multiflorum (E+ or E-), Schedonorus arundinaceus (E+ or E-) and Bromus catharticus (which does not establish associations with Epichloë) were sown as B. auleticus neighbors. While B. auleticus E+ plants induced a significant increase in mycorrhizal colonization of the neighbor grasses, even higher in the E- neighbor plants (L. multiflorum and S. arundinaceus), in comparison to B. auleticus E- neighbors, seedling emergence, root length, leaf number or shoot dry weight were not affected. This is the first approach to studying these triple interactions (endophyte-grass-mycorrhiza) involving wild and forage grasses in the field. Our results show that the effect of Epichloë extends further than its own host and suggest an interaction among endophytes of heterospecific neighbors at the rhizosphere level. •Epichloë-native grass symbiota promote mycorrhizal colonization in neighbor grasses.•The influence of Epichloë on mycorrhizal colonization is greater in E- neighbors.•Growth parameters do not correlate with mycorrhizal colonization.