Two tomato root colonizing strains, Bacillus amyloliquefacien CM-2 and T-5, were isolated after the enrichment procedure on the roots of tomato seedlings, and evaluated for their antagonistic activities against pathogenic Ralstonia solanacearum (RS) in vitro. Three inoculation methods were used to test their biocontrol efficacy and growth promotion effects in greenhouse based on their colonization ability in rhizosphere soil. Both CM-2 and T-5 strains showed strong biocontrol and growth promotion effects on tomato seedlings. The best biocontrol efficacy was obtained by treating both seedlings and soils with the biocontrol agents. In comparison to the control, the disease incidence was reduced by 70.1 and 79.4%
for CM-2 and T-5, respectively. The numbers of colony-forming units of RS in rhizosphere soil were significantly
(P < 0.05) decreased as compared to the control. The density of both strains in the rhizosphere soils remained at a high level (107 CFU/g) during a five-week period. Both strains were recovered from the interior of the stems and roots of plants. They showed positive reactions for ammoina, indole acetic acid and siderophores production, and phosphate solubilizing activity. Our data proved the potential of isolated strains for the biocontrol of tomato bacterial wilt.