Résumé
Scientists of agriculture and plant pathology are on the lookout for potential biological control agents to control the plant pathogenic organisms in order to avoid soil contamination. Rhizospheric bacteria are excellent agents to control soil-borne plant pathogens. In this study an attempt has been made to evaluate the antagonistic activity of a bacterial strain Bacillus circulans against Curvularia lunata, Alternaria alternata and Cladosporium sp., which are important seed and soil borne pathogens distributed throughout the world. These infections cause grain mold and leaf spot diseases, resulting in significant economic loss to the crops. A soil bacterium Bacillus circulans isolated from the rhizospheric soil of Vigna unguiculata, showed high antagonistic activity against Curvularia lunata, Alternaria alternata and Cladosporium sp. on dual plate assay. Bacillus circulans showed a distinct inhibition zone in the dual plate assay and also produced a clear inhibition zone in chitin amended agar medium containing 0.5% colloidal chitin, indicating that it secretes chitinase.