A novel plant-fungal mutualism associated with fire

► Thermotolerant fungi (e.g. Morchella) were isolated from fire-adapted cheatgrass. ► Non-mycorrhizal Morchella infected cheatgrass roots and grew into stem tissue. ► Morchella increased biomass and fecundity of its local cheatgrass population. ► Morchella increased survival of seed exposed to heat typical of cheatgrass fires. ► The Morchella-cheatgrass mutualism was evolutionarily novel.