Biochemical and molecular characterization of Bacillus isolates with distinct antagonistic potential against the bacterial pathogen of tomato wilt

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Soad Ali
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Eighty-one isolates of Bacillus were evaluated for their ability to inhibit the growth of Ralslonia solanacearum, the causal agent of bacterial wilt of tomato in vitro. Twelve isolates showed inhibitory effect on bacteria growth. Five isolates B2, B5, B7, B8 and BO were identified as Bacillus brevis, B. subtilis KL-077, B. subillis BS-2, B.subtilis BS-land Bacillus sp by bacteriological assays, Biolog test and 16s rDNA sequence analysis. The isolate of Bacillus brevis produced the highest inhibition zone followed by the B.subtilis strain KL-077, BS-land BS-LThese isolates and one biological product (AN DI of Bacillus cereus selected, were tested for their ability to promote growth and induce resistance of tomato plants against the bacterial wilt in sterile and non-sterile soil under green house conditions. Bacterization of tomato seed by the Bacillus isolates was found to be effective in controlling tomato wilt than treated seedling with B. cereus biological product and non-treated control. Most of Bacillus isolates promoted plant growth that was measured by seed germination, plant height, fresh weight, dry weight and number of fruits per plant. Likewise all isolates significantly reduced the percentage of infection in sterile and non-sterile soil as compared with non-treated control, however, the rate of growth enhancement and disease suppression varied considerably with isolates. Bacillus brevis B2 besides being the best growth promoters was also the most efficient resistance inducer, which reduced the percentage of infection by 66.67% and 53.48% in sterile and non-sterile soil, respectively. Isolate Bacillus sp BO, and B. cereus biological product showed less effectiveness in growth promotion and disease resistance.
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Biochemical ,Bacillus,pathogen,tomato