Pathogenicity of Beauveria bassiana and production of cuticle-degrading enzymes in the presence of Diatraea saccharalis cuticle

Abstract

The sugarcane borer, Diatraea saccharalis, is one of the worst pests in Brazilian sugarcane crop, causing high levels of financial losses every year. Beauveria bassiana is an entomopathogenic fungus widely used in the biological control of several agricultural pests. The aims of this study were to: (1) evaluate the pathogenicity of B. bassiana strains against D. saccharalis (2) investigate the production of proteases and chitinase by B. bassiana in the presence of the cuticle of sugarcane borer; and, (3) evaluate the relation between the production of enzymes and pathogenicity of the strains. All isolates tested were pathogenic to D. saccharalis and the mortality ranged from 36 to 88%. The production of enzymes was higher in the medium containing cuticle, showing that the process is stimulated by specific components found in the cuticle of the host. Pr1 activity was higher than Pr2 and both were produced at 24 h. The highest production of chitinase was obtained at 96 h of culture for all strains tested. Levels of specific cuticle-degrading enzymes such as proteases correlated positively with specific virulence parameters. B. bassiana URM2915 showed promising features to be used in a biological control program of D. saccharalis.

Key words: Biological control, sugarcane, subtilisin-like protease, trypsin-like protease, chitinase.