Mycorrhizal association and their role in plant disease protection

Abstract

The arbuscular mycorrhizal (AM) symbiosis is a mutualistic association formed between plants and soil fungi. Members of AM-forming fungi (AMF) belong to the phylum Glomeromycota. They are symbiotically associated with roots of more than 80 % of terrestrial plant species. AM fungi are obligate biotrophs that require the host plant to proliferate, survive, and complete their life cycle. The AMF, during the symbiosis, establish a sink for plant photosynthate by utilizing it for biomass and metabolic energy, while the AM plants obtain nutrients and water through the AMF hyphae. The benefits of AM symbiosis on fitness plants are largely known, including a better mineral nutrition and a higher tolerance of mycorrhizal plants to abiotic stresses, such as drought, salinity, and presence of heavy metals. Additionally, recent investigations reveal that AMF can suppress pests and plant diseases through induction of systemic resistance. The knowledge about the mechanisms behind the induction of resistance by mycorrhizal symbiosis remains unknown. This chapter describes the role of mycorrhizal symbiosis in plant disease protection, with special emphasis on the mycorrhiza-induced resistance (MIR).