Abstract

Mycorrhizal fungi constitute a key functional group of soil biota that greatly contribute to productivity
and sustainability of terrestrial ecosystems. The benefits of mycorrhizal symbiosis to the host plant
have usually been considered as a result of closed relationships between the host plant and the fungal
symbiont. However, the extramatrical mycelium provides an increased area for interactions with other soil
microorganisms by enhancing the development of the host plant root systems. Mycorrhizal fungi act as
a bridge connecting the rhizosphere to the bulk soil and, through an active development of extraradical
mycelium into the soil, this soil compartment (mycorrhizosphere) extends root–fungal interactions with
soil microbial communities. Interactions within the mycorrhizosphere microbial community are of special
interest because some microorganisms associated with mycorrhiza may complement mycorrhizal activities.
The purpose of this chapter is to outline the mycorrhizosphere interactions between ectomycorrhizal fungi
associated with forest tree species and soil microflora of potentially synergistic properties that lead to
stimulation of plant growth. By focussing on the ectomycorrhizal symbiosis associated with Tropical
and Mediterranean tree species, we will review the global effects of ectomycorrhizal symbiosis on the
functional diversity of soil microflora and in particular, the interactions between ectomycorrhizal fungi
and some plant-growth-promoting rhizobacteria. This review will focus on the interactions between
ectomycorrhizal fungi and soil microflora leading to a sustainable microbial complex ecosystem with high
efficiency against phosphorus mobilization and transferring phosphorus from the soil organic matter or
from soil minerals to the host plant.