Mycorrhizal research — a priority in agriculture

Abstract

The vesicular arbuscular mycorrhizae (VAM) help in conversion of arid soil to fertile and productive soil. VAM fungi increase plant growth through enhanced nutrient uptake and cycling of phosphorus, nitrogen, carbon, zinc, copper and other minerals. The bacteria associated with mycorrhizal fungi solubilize P which is transported through the mycorrhizal fungi to plant. Mycorrhizal fungal hyphae produce phosphatases and organic acids that enhance the availability of soil P by weathering P from the clay matrix and maintaining the solution P by binding Ca with the secreted oxalates. There are reports that N fixed by one plant has been transported to an adjacent, non-fixing plant through mycorrhizal fungal hyphae. Mycorrhizal hyphae form aggregates by directly binding soil particles possibly by producing polysaccharides. These aggregates are a major input into systems with low organic matter. Apart from nutrient uptake, mycorrhizae also enhance the transport of water from soil to plant. VAM fungal inoculated plants exhibit increased drought resistance and resistance to fungal root diseases and nematode diseases. VAM fungi initiate host defence response in roots by increasing phenols, peroxidases, phytoalexins etc. VAM fungi by synergistic action with nitrogen fixing nodulating organisms enhance mineral nutrition and growth of crop plants. Agricultural practices such as fallowing, tillage, top soil removal, fires, water logging and the use of chemicals like pesticides and fertilizers can influence VAM inoculum potential. Large differences exist between plant species in their dependence of VAM fungi for uptake and growth. The selection of VAM fungi, inoculum production and inoculation techniques are important factors which play a major role in favouring good results of VAM fungi for agricultural systems. The benefits of VAM fungi for sustainable agriculture are immense.