We examined the effects of an ectomycorrhizal
(EM) fungus, Pisolithus sp., on of the growth of
Pinus halepensis (Allepo pine) seedlings, soil microbial
functions and rock phosphate solubilization in a
un-disinfected soil amended or not with a Moroccan
rock phosphate. Allepo pine seedlings were inoculated
with an EM fungus (Pisolithus sp. strain PH4) isolated
from a P. halepensis plantation and selected for its
high ability to mobilize P from an inorganic form of
phosphate. After 4 month’s culture in a disinfected
substrate, plants were transferred in 10 l-containers
filled with a natural forest soil and amended or not with
rock phosphate powder. After 12 month’s culturing, the
growth, needle nutrient concentrations of P. halepensis
plants were measured. Soil microbial catabolic diversity
was assessed by measuring CO2 production of
substrate induced respiration responses. Fluorescent
pseudomonads were isolated from each soil treatment
and tested in axenic conditions for their ability to
solubilize a source of inorganic phosphate. The results
clearly showed that (i) P. halepensis growth was greatly
promoted by the presence of the ectomycorrhizal
fungus Pisolithus strain PH4 in a disinfected soil/
vermiculite mixture and in a non disinfected soil, (ii)
ectomycorrhizal inoculation induced significant
changes in the functions of soil microbial communities
and selected microorganisms potentially beneficial to
the plant growth (i.e. phosphate-solubilizing fluorescent
pseudomonad) and (iii) rock phosphate solubilisation
was mainly dependent on EM inoculation and mycorrhizosphere
microorganisms. These results were in
accordance with previous studies where it was demonstrated
that EM symbiosis has a beneficial effect on
plant growth through a direct effect on the host plant but
also an indirect effect via a selective pressure on soil
microbiota that favours microorganisms potentially
beneficial to plant growth.