Short communication : Antagonistic activity by Bacillus subtilis againts Xanthomonas campestris pv. glycines under controlled conditions

Abstract

Xanthomonas campestris pv. glycines (Nakano) Dye is the causal agent of bacterial pustule in soybean (Glycinemax L.) Merrill. Two tests were carried out using 175 bacteria isolated in a previous work from the soybean leafletsor phyllosphere: the first one for susceptibility to three antimicrobial agents (penicillin, streptomycin and rifampicin)applied at two different doses (20 and 100 µg ml-1), and the second one for antagonism towards X. campestris. Eighteenbacterial isolates (10.3%) were resistant to penicillin and five (2.8%) to streptomycin at 100 µg ml-1; only 2% ofthe phyllosphere bacteria were resistant to rifampicin at 20 µg ml-1. Isolate 210, identified as Bacillus subtilis, was resistantto rifampicin at 20 µg ml-1, showed the highest degree of antibiosis against the pathogen and was further testedfor antagonism against the pathogenic bacteria under greenhouse conditions. In the inoculation study, treatmentof soybean leaf surfaces with B. subtilis 210 72 h before the inoculation with the pathogenic bacteria, reduced thenumber of lesions by X. campestris. There were significant differences with other treatments (P