Effect of Pichia membranaefaciens on ROS metabolism and postharvest disease control in citrus fruit

• Pichia membranaefaciens reduced disease incidence and lesion diameter in citrus.
• Yeast treatment enhanced the levels of O2− and H2O2 in citrus peel.
• Yeast treatment stimulated the activities of antioxidant enzymes in citrus peel.
• Yeast treatment could regulate the ascorbate–glutathione cycle in citrus peel.

The yeast Pichia membranaefaciens has antagonistic effects against a wide range of phytopathogenic fungi that cause postharvest fruit decay. This work evaluated the effects of P. membranaefaciens on the reactive oxygen species (ROS) metabolism and disease control in harvested citrus fruit (Citrus sinensis L. Osbeck). The lesion diameter caused by Penicillium italicum and Penicillium digitatum on citrus fruit was remarkably reduced when the fruit was point-inoculated or dipped in a suspension of P. membranaefaciens at 1 × 108 CFU mL−1. The application of P. membranaefaciens on citrus fruit enhanced the activity of superoxide dismutase, ascorbate peroxidase, and glutathione reductase, as well as the levels of hydrogen peroxide, the superoxide anion and glutathione, but inhibited the decreasing ascorbic acid content. Furthermore, catalase activity was decreased by the same treatment. These results indicated that yeast treatment induced the synthesis of antioxidant enzymes which might have antagonistic effects against postharvest green and blue mold infection in citrus fruit.