Antagonistic potential of Bacillus spp. isolates against bacterial pathogens of tomato and fungal pathogen of pepper

Abstract

In vitro antagonistic potential of eleven isolates of Bacillus spp. against two phytopathogenic bacteria and one fungus was tested in order to identify potential biocontrol agents in vegetable crops. The Bacillus spp. isolates demonstrated different levels of antagonistic effect against the tested pathogenic microorganisms. Data in the study proved Xanthomonas vesicatoria to be more sensitive to Bacillus spp. strains than Clavibacter michiganensis subsp. michiganensis. Ten B. subtilis strains induced growth inhibition of X. vesicatoria, while a strain of B. pumilus did not affect the growth of that bacterium. The largest inhibition zones against X. vesicatoria were induced by strains B-319, B-325 and B-358. The pathogenic strain C. michiganensis subsp. michiganensis was most inhibited by two B. subtilis strains (B-338 and B-348) with mean inhibition zone diameters of up to 20 mm. B. subtilis strain B-319 which was the best in inhibiting X. vesicatoria, showed the lowest inhibitory effect on C. michiganensis subsp. michiganensis. The largest growth inhibition percentage of Verticillium sp. (PGI approximately 70%) was induced by B. subtilis strains B-310 and B-322. The other B. subtilis strains showed PGI values ranging from 45% to 68%, while B. pumilus strain B-335 had the least antagonistic potential (PGI =34.43%) against the pathogen. This study identified at least one suitable biocontrol candidate, B. subtilis strain B-358, as effective in vitro against all three vegetable pathogens.