Epichloë endophyte affects the root colonization pattern of belowground symbionts in a wild grass

Plants host multiple symbionts that interact with each other affecting plant performance and regulating their establishment. Here, we analyzed how the association with Epichloë endophytes affects belowground colonization by Dark Septate Endophytes (DSE) and arbuscular mycorrhizal fungi (AMF) in the grass Bromus auleticus. Epichloë-symbiotic (E+) and Epichloë-non symbiotic (E−) plants were sampled from a long-term experimental plot and colonization structures were analyzed in the roots. We also examined the influence of Epichloë exudates on the in vitro growth of DSE Microdochium bolleyi isolated from roots. Epichloë symbiosis increased AMF colonization, although differences were not significant. Despite the lack of differences in total DSE colonization, in concordance with in vitro findings, a higher significant abundance of microsclerotia was observed in E+ plants. A negative correlation between total mycorrhizal and DSE was found. Our findings show a more uniform root colonization pattern in E+ plants, suggesting a root symbiosis modulating role. •DSE microsclerotia was significantly more abundant in B. auleticus E+ plants than E−.•Arbuscules abundance was double in plants associated with Epichloë compared to E−.•Epichloë endophytes exudates did not affect DSE strain growth in vitro.•DSE negatively correlate with AMF colonization.•E+ plants presents a more uniform root colonization pattern than Eplichloë-free.