Biocontrol of plant pathogens using arbuscular mycorrhizal fungi

Mycorrhizal fungi colonise the roots of over 90% of plant species, to the mutual benefit of both the plant host and fungus. These symbiotic fungi are present in most terrestrial ecosystems and play a major role in both the growth of plants and important ecosystem processes. Although there are several different types by far the most common are the arbuscular mycorrhizas which are formed by most plant species, including the majority of commercially important crop and horticultural plants. The hyphae of the symbiotic fungi penetrate roots of susceptible plants forming specialised structures known as arbuscles, and also sometimes vesicles; mycorrhizal hyphae form an extensive mycelium within and outside the root which extends into the soil, often several centimetres. These hyphae often bear spores but in some species of arbuscular mycorrhical fungi (AMF) these often also occur intra-radically. Each structure has a different function. Arbuscles are the structures where exchanges of carbon to the fungus and nutrients and water to the host plant take place and vesicles are considered to be primarily for storage. The external mycelium serves as an acquisition and transfer system and the spores a means of survival. The association between the AMF and plants thus brings major advantages to both partners. The fungus obtains a source of carbon derived from plant photosynthesis and so does not have to compete for scarce rhizophere carbon in order to survive and proliferate and the host plant receives several benefits.