Identification of lipopeptide antibiotics of a Bacillus subtilis isolate and their control of Fusarium graminearum diseases in maize and wheat

Abstract

Substances produced by Bacillus subtilis D1/2, a bacterium isolated from cultivated soil, were found to inhibit Fusarium graminearum. The antifungal activity of the bacterium was attributable to major extracellular lipopeptides isolated and identified as fengycins. Their synthesis was enhanced by casamino acids added to the culture medium. The unpurified cell-free spent medium elicited hemolysis with increasing concentration. Its application to field-cultivated maize and chamber-grown wheat suppressed gibberella ear rot and Fusarium head blight, respectively, when the plants were inoculated with F. graminearum macroconidia. The treatment of maize ears consistently arrested ear-rot development, while the treatment of wheat spikes retarded the progress of Fusarium head blight. Although the deoxynivalenol and ergosterol contents of treated maize kernels were halved, they remained high because of the experimental requirement to inoculate with a high number (1.5 × 104) of macroconidia. As a potential antifungal agent for controlling Fusarium diseases, B. subtilis D1/2 can be further developed as a useful component of integrated pest management. © Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada 2009.