Root colonization by inoculated plant growth-promoting rhizobacteria

Certain rhizobacteria referred to as 'plant growth-promoting rhizobacteria' (PGPR) can contribute to the biological control of plant pathogens and imp rove plant growth. They enhance root development either directly by produci ng phytohormones, or indirectly by inhibiting pathogens through the synthes is of different compounds. PGPR are likely to be of great interest in susta inable crop protection and have drawn much attention in recent years. Howev er, the use of these bacteria to protect crops sometimes fails because rhiz obacteria are unable to recolonize the rhizosphere of inoculated plants. Th e colonization of roots by inoculated bacteria is an important step in the interaction between beneficial bacteria and the host plant. However, it is a complex phenomenon influenced by many biotic and abiotic parameters, some of which are now apparent. This paper summarises knowledge on rhizosphere colonization by PGPR.