Plant growth-promoting rhizobacteria (PGPR) competitively colonize plant roots, and stimulate plant growth and/or reduce the incidence of plant disease. The PGPR concept has been vindicated by the isolation of many bacterial strains that fulfill at least two of the three criteria described above (aggressive colonization, plant growth stimulation and biocontrol). In PGPR, which are sometimes called biopesticides, the biocontrol aspect is most conspicuous. These PGPR, which mostly belong to Pseudomonas spp., are antagonists of recognized root pathogens.
