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.