The mycorrhizosphere effect: a multitrophic interaction complex improves mycorrhizal symbiosis and plant growth

Mycorrhizal fungi are essential components of sustainable soil-plant systems. Hyphae of arbuscular mycorrhizal (AM) fungi play important role in the formation and stability of soil aggregates and contribute to the composition of plant community structures. Mycorrhizal symbiosis generally increases root exudation and influences rhizosphere microbial communities. Mycorrhizal hyphae exude chemical compounds that have a selective effect on the microbial communities in the rhizosphere and in the soil. These microbial compartments are commonly named "mycorrhizosphere" and there has been increasing evidence that the mycorrhizosphere communities have an important role in plant growth and soil fertility. For instance, it has been demonstrated that mycorrhizal fungi had a selective effect on bacteria potentially beneficial to the symbiosis and to the plants. Hence, mycorrhizal symbiosis provides a microbial complex regulated by multitrophic interactions. This fungal symbiosis had an indirect effect on plant growth through its selective pressure on mycorrhizosphere communities in addition to its classical direct effect. This chapter presents highlights on multitrophic interactions and its importance in sustainable agriculture, especially in tropical and mediterranean countries. (Résumé d'auteur