Evaluation of Bacillus spp. isolates as potential biocontrol agents against charcoal rot caused by Macrophomina phaseolina on common bean

The fungus Macrophomina phaseolina, the causal agent of charcoal rot of common beans, damages the roots, stems, and leaves of seedlings and plants and forms resistant structures, so that chemicals are not sufficient for disease control. Integrated management systems associated with the use of biological control techniques are a sustainable alternative. Here we collected 37 native bacterial isolates from the common bean rhizosphere and screened them for antagonistic activity against M. phaseolina. Four isolates (BA97, BN17, BN20, and BR20) identified as Bacillus spp. showed antagonism in vitro against M. phaseolina, inhibiting its growth by 62.5–85%. In an in planta antagonistic assay, isolate BN20 reduced disease severity the most. Isolates BA97, BN17, BN20, and BR20 produced volatile compounds as a mechanism of antagonism. They also produced indole acetic acid in vitro (1.98–3.87 μg/ml). These results suggest that seed bacterization with the rhizobacterial isolates for field planting may be an effective means to reduce crop damage by M. phaseolina.