Abstract

Volatile organic compounds (VOCs) produced by the yeast Saccharomyces cerevisiae strain CR-1 are able to inhibit the development of the fungal phytopathogen Guignardia citricarpa, causal agent of the disease citrus black spot. Antimicrobial VOCs have potential applications to control plant pathogens; however, there is limited information on the action mechanisms. It is possible that VOCs trigger the accumulation of harmful levels of reactive oxygen species. Therefore, this work aimed to evaluate the effect of the artificial mixture of VOCs, constituted by alcohols and esters identified from S. cerevisiae, on the antioxidant system of G. citricarpa. The VOCs at 0.48 μl/ml of air space completely suppressed the mycelial growth and reduced the respiratory rate. Increased activity of the antioxidant enzymes superoxide dismutase and catalase in the first 24 to 48 h of exposure to the VOCs indicating intracellular accumulation O₂^•- and H₂O₂, respectively was observed; however, the antioxidant glutathione pathway was not activated. In addition, increased lipid peroxidation was detected, confirming the oxidative stress process. Therefore, it was reported for the first time the disruption of the cellular redox homeostasis in microorganisms caused by VOCs. This knowledge is important to better understand the action mechanisms of antimicrobial volatiles and to develop safer fumigants to control postharvest diseases.

Key words: Antifungal, citrus, fumigation, stress response.