Biological control of bacterial leaf streak of corn using systemic resistance-inducing Bacillus strains

Abstract

Management options are needed for emerging bacterial diseases such as bacterial leaf streak of corn (maize), caused by Xanthomonas vasicola pv. vasculorum (Xvv). The objective of this study was to determine the potential for seed treatment with strains of Bacillus spp. to provide control of bacterial leaf streak. In two trials of a greenhouse pot experiment, B. pumilus R190 and B. subtilis 6051 were applied to corn seed prior to planting, and the plants were grown to V3 stage when they were inoculated with Xvv. Inoculation in Trial 1 was performed by streaking Xvv cells onto leaf surfaces, while leaves were sprayed with a bacterial cell suspension in Trial 2. In both trials, extensive lesion development occurred on leaves of the no-bacteria control 14 days after pathogen inoculation. Seed treatment with B. pumilus R190 reduced disease severity significantly by 85% and 56% compared to the control in Trial 1 and Trial 2, respectively. Disease severity was reduced by seed treatment with B. subtilis 6051 by 32% and 52% in Trial 1 and Trial 2, respectively, with the disease reduction being statistically significant only in Trial 2. The reduction in the foliar disease resulting from the application of bacteria to seed was an indication that induced systemic resistance was involved as the biological control mechanism. This is the first demonstration that root-colonizing bacteria have potential as biocontrol agents to suppress a foliar bacterial disease in corn.