Comparative performance of Bacillus spp. in growth promotion and (suppression) of tomato bacterial wilt caused by Ralstonia solanacearum

Forty-seven isolates of Bacillus were evaluated for their ability to inhibit the growth of Ralstonia solanacearum, the causal agent of bacterial wilt of tomato in vitro. Twelve isolates showed inhibitory effect on bacteria growth. Five of them were identified as Bacillus subtilis, B. amyloliquefaciens and B. licheniformis by bacteriological assays and Biolog test. The isolate of B. subtilis produced the highest inhibition zone followed by that of B. amyloliquefaciens and B. licheniformis. They were also tested for their ability to promote growth and induce resistance of tomato plants against the bacterial wilt in the green house conditions. Bacterization of tomato seed by the Bacillus isolates was found to be effective in controlling the tomato wilt. Compared with the control most of Bacillus isolates promoted plant growth that was measured by seed germination, plant height, fresh weight and dry weight. Likewise all isolates significantly reduced the infection percentage compared with non-treated control, however, the rate of growth enhancement and disease suppression varied considerably with isolates. The isolate of Bacillus subtilis besides being the best growth promoters was also the most efficient resistance inducers, which reduced the infection percentage by 80.0. The study demonstrates a potential role for Bacillus species in bacterial wilt management.