Evaluation of the Antagonistic Activity of Metabolites Produced by the Culture of Bacillus halotolerans to Control Rhizoctonia solani

The use of antagonistic metabolites in soils where their natural presence can be reduced by the agricultural activity itself, represents a sustainable environmental friendly technology to control Rhizoctonia solani. Our objective is to evaluate the antagonistic activity of metabolites produced by the strain Bacillus halotolerans IcBac02.1 cultivated in mineral medium in a batch system at the level of stirred tank bioreactor. The presence of antibiotic metabolites was determined from cell-free supernatant, for which it was concentrated and fractionated with organic solvents of increasing polarity; butanolic phase was concentrated, freeze-dried and fractionated using the Flash chromatography technique with different systems of acetonitrile: water. F3 fraction showed greater inhibition of mycelial growth against R. solani under in vitro conditions using the plate diffusion technique. Also, the presence of hydrolytic enzymes such as cellulases, proteases and amylases was determined by colorimetric techniques. At greenhouse level, cell-free supernatant and F3 fraction were inoculated at the base of 1-week-old common bean cv Canario Centenario plants before infecting the plants with R. solani. Our results showed that both treatments significantly reduce the incidence of the disease by 50% after ten days of evaluation, due to the action of antibiotic metabolites and hydrolytic enzymes. Therefore, the use of antagonistic metabolites produced by the culture of B. halotolerans represents a promising alternative for phytopathogens control.

Key words: rhizosphere, Rhizoctonia solani, antagonistic metabolites, fermentation

Acknowledgments: Project 158-PNCIP-PIAP-2015 of Innovate Perú