Oxidative stress response of Beauveria bassiana to Bordeaux mixture and its influence on fungus growth and development

BACKGROUND: Chemical fungicides used to manage plant diseases may negatively affect beneficial fungi such as entomopathogens. In this study, the participation of the antioxidative system in the entomopathogenic fungus Beauveria bassiana exposed to the copper-based Bordeaux mixture fungicide and its relation with fungus growth and development were examined. The fungus was grown in submerged culture containing Bordeaux mixture at the recommended dose. Within the first 24 h of elicitation, the vegetative growth, germination, sporulation and activity of amylase and laccase and the antioxidative enzymes catalase (CAT) and superoxide dismutase (SOD), as well as the production of hydrogen peroxide (H2O2), were evaluated. RESULTS: Bordeaux mixture inhibited B. bassiana germination (between 65 and 88%) and sporulation (between 15 and 57%) and significantly increased laccase production (>= 130%), especially within the first 4 h of fungus exposure. By contrast, the mycelial growth was found to be less affected by the fungicide. These effects were accompanied with a significant increase in H2O2 levels in fungal cells, as well as in SOD activity, but not in CAT, showing clear signs of increased oxidative stress. CONCLUSION: The effect of Bordeaux mixture on B. bassiana development was probably due to the toxicity of the copper ion itself, and it also induced an oxidative state in fungal cells. (C) 2013 Society of Chemical Industry