Effects of simultaneous infections of endophytic fungi and arbuscular mycorrhizal fungi on the growth of their shared host grass Achnatherum sibiricum under varying N and P supply

Grasses can be infected by endophytic fungi and arbuscular mycorrhizal (AM) fungi simultaneously. Here, we investigated the interactions of a native grass, Achnatherum sibiricum, with both endophytic and AM fungi (Glomus mosseae, GM and Glomus etunicatum, GE) at different nitrogen (N) and phosphorus (P) levels. The results showed that endophyte infection significantly suppressed the colonization rates and spore density of GE, but had no effect on those of GM. Endophyte infection increased shoot biomass regardless of the nutrient conditions. The effects of AM fungi on host growth were dependent on mycorrhizal species. There was no significant interaction between endophytic fungi and GE on host growth; however, a significant interaction between endophytic fungi and GE occurred in total phenolic concentrations and P uptake. As for GM, a significant interaction among endophytic fungi, AM fungi and nutrient availability occurred in shoot growth. Under sufficient N and P conditions, endophyte infection alleviated the detrimental effects of GM colonization on host growth.