Effects of Inoculation with PGPR Bacillus and Pisolithus tinctorius on Pinus pinea L. Growth, Bacterial Rhizosphere Colonization, and Mycorrhizal Infection

The effect of co-inoculation with Pisolithus tinctorius and a PGPR belonging to the genus Bacillus (Bacillus licheniformis CECT 5106 and Bacillus pumilus CECT 5105) in enhancing growth of Pinus pinea plants and the changes that occurred in rhizosphere microbial communities and the degree of mycorrhization were evaluated. Both bacterial strains of Bacillus promote the growth of Pinus pinea seedlings, but this biological effect does not imply a synergic effect with mycorrhizal infection. However, the positive response to mycorrhiza in a longer-term experiment it could be expected. The introduction of both inocula causes an lateration in the microbial rhizosphere composition, despite the low levels of inocula that were found at the end of the assay.