Caffeic acid increases the fitness of Candida oleophila to the microenvironment of kiwifruit and its biocontrol performance against postharvest decay fungi

Reactive oxygen species (ROS) in harvested fruit wound tissues result in an oxidative microenvironment. The pretreatment of some antagonistic yeasts with stress-ameliorating compounds has been shown to enhance tolerance to subsequent exposure to oxidative stress and thus improves biocontrol performance. The effect of caffeic acid (CA) on ROS in Candida oleophila was investigated after administration to kiwifruit wounds. CA treatment enhanced the tolerance of C. oleophila to the microenvironment of kiwifruit wounds. CA-treated yeast recovered from the microenvironment had lower ROS, less mitochondrial impairment and cellular oxidative damage, relative to non-CA (NCA) treated yeast. CA-treated yeast also exhibited improved biocontrol efficacy on kiwifruit against the decay fungi, Botrytis cinerea and Penicillium expansum, and more rapid growth in fruit wounds, than NCA-treated yeast. The antioxidant gene expression of C. oleophila was elicited by the CA treatment. In conclusion, the activation of antioxidant response induced by the by CA treatment of C. oleophila contributed to enhanced tolerance to oxidative stress and improved biocontrol efficacy against postharvest decay fungi.