The role of fungal networks in modulating plant symbioses with competing root symbionts

Most plants form mutualistic symbioses with arbuscular mycorrhizal fungi (AMF), forming complex, below-ground networks which connect neighbouring plants via shared fungal hyphae known as a common mycelial network (CMN). Through CMNs, AMF supply their plant partners with otherwise-inaccessible soil nutrients in return for photosynthetically-fixed carbon from across the network. However, plants rarely associate with mutualists alone. Instead, AMF often occupy root systems alongside parasites, such as plant parasitic nematodes (PPN), simultaneously with ramifications for plant growth and yield - pertinent considerations for natural and agroecosystems. The effect of competing root symbionts on mycorrhizal carbon-for-nutrient exchange across CMNs is unknown; the overarching question of whether or not plants can regulate provision of resources to "reward" beneficial partners and "sanction" parasites and the role of the CMN in supplementing C supply to symbionts being hotly debated.