Role of antibiosis on suppression of bacterial common blight disease in French bean by Paenibacillus polymyxa strain HKA-15

Paenibacillus polymyxa strain HKA-15, a soybean bacterial endophyte showed strong antagonism against bacterial common blight pathogen Xanthomonas campestris pv. phaseoli strains M-5 and CP-1-1. In agar diffusion assay, the antibacterial metabolite from P. polymyxa HKA-15 showed a clear zone of inhibition against M-5 and CP-1-1. Under phytotron conditions, the biocontrol activity of P. polymyxa HKA-15 against bacterial common blight pathogen X. campestris pv. phaseoli M-5 was assessed. At four days after inoculation of M-5, lowest mean disease rate (MDR) (1.13) and percent disease incidence (PDI) (28.25) were recorded in streptomycin sulphate at 100 ppm as positive chemical treatment. The application of crude metabolite from P. polymyxa HKA-15 at 100 ppm was on par with positive chemical control in suppression of bacterial common blight disease in French bean plants.Key words: Antibacterial activity, biocontrol, French bean, Paenibacillus polymyxa, Xanthomonas campestris pv. phaseoli