Improved adaptation of temperate grasses through mutualism with fungal endophytes.

Abstract Plants provide a unique ecological niche for diverse communities of fungal endophytes that vary in their impact, positive to negative, on the host plant. Fungal endophytes colonize plants without any visible disease symptoms for at least part of their life history. These symbionts are critical components of natural and semi-natural ecosystems, as well as cultivated agricultural communities, dramatically influencing plant adaptation and evolution. Many temperate grass species are reliant on their mutualistic association with obligate fungal endophytes of the genus Epichloë for a variety of fitness benefits, such as persistence under both invertebrate and vertebrate grazing pressure and improved adaptation to abiotic stresses. In New Zealand, Epichloë endophytes have been estimated to contribute $200 m per year in increased animal production through improved pasture persistence and yield. Other fungal endophytes have also been studied in temperate grasses, although much less is understood about the biological and economic impacts of these plant-fungal interactions. Determining which fungal endophytes are mutualistic has been, and continues to be, a challenge, particularly as we begin to realize that endophytes interact with other endophytes and little is understood about what factors shape endophyte community structures.