Activity of cells, filtered and autoclaved bacterial broth of <em>Bacillus spp.</em> asbiological control agents of <em>Colletotrichum acutatum</em>

Abstract

The utilization of biological control agents has been studied in many crop species, having been found to be antagonism a promising method in plant diseases control. The present study aimed to evaluate "in vitro" between Bacillus spp. isolates and Colletotrichum acutatum. For this purpose, it was analyzed the influence of cells, filtered and autoclaved as inhibitors of C. acutatum conidial germination and mycelium growth. Ten bacterial isolates from biological control agents were tested for antagonism to one C. acutatum isolate. The isolates that showed the highest levels of antagonism were utilized to prepare a bacterial broth of each one. Part of this was maintained intact, a second part was filtered in Millipore^® membrane and the last one was autoclaved. Three essays were set to verify the action of isolates on mycelium growth, colony development, and the effect on conidial germination. Bacillus spp. isolates were able to produce metabolites in sufficient amount to inhibit the germination and mycelium growth of the plant pathogen. However, in the treatment subjected to high temperature (autoclaved broth), no effect on the fungus was verified, this being understood as an indication that the metabolites produced by the bacterium are thermolabiles. Additional keywords: biological control; metabolites; antagonism.