Arbuscular Mycorrhizal Fungi as Potential Bioprotectants Against Plant Pathogens

Abstract

Arbuscular Mycorhizal (AM) fungi are ubiquitous and form symbiotic relationships with roots of most terrestrial plants. Their associations benefit plant nutrition, growth and survival due to their enhanced exploitation of soil nutrients. These fungi play a key role in nutrient cycling and also protect plants against environmental and cultural stresses. The establishment of AM fungi in the plant root has been shown to reduce the damage caused by soil-borne plant pathogens with the enhancement of resistance in mycorrhizal plants. The effectiveness of AM fungi in biocontrol is dependent on the AM fungus involved, as well as the substrate and host plant. However, protection offered by AM fungi is not effective against all the plant pathogens and is modulated by soil and other environmental conditions. AM fungi generally reduce the severity of plant diseases to various crops suggesting that they may be used as potential tool in disease management. AM fungi modify the quality and abundance of rhizosphere microflora and alter overall rhizosphere microbial activity. These fungi induce changes in the host root exudation pattern following host colonization which alters the microbial equilibrium in the mycorrhizosphere. Given the high cost of inorganic fertilizers and health hazards associated with chemical pesticides, AM fungi may be most suitable for sustainable agriculture and also for increasing the yield of several crops through biocontrol of plant pathogens. This chapter provides an overview of mechanisms of interaction which take place between soil-borne plant pathogens and AM fungi on different plants. The availability of new tools and techniques for the study of microbial interactions in the rhizosphere may provide a greater understanding of biocontrol processes in the near-future.