Combining an antagonistic yeast with harpin treatment to control postharvest decay of kiwifruit

• C. diversa or harpin effectively controlled postharvest decay of kiwifruit.
• Harpin enhanced biocontrol efficacy of C. diversa against postharvest decay.
• C. diversa and harpin alone or in combination induced kiwi defense response.
• An integrated strategy of C. diversa and harpin treatment is a promising approach.

Integrated management, utilizing different non-chemical methods, is an approach to controlling postharvest losses that is being actively investigated. In the present study, the use of an antagonistic yeast, Candida diversa, combined with harpin (a hypersensitive response elicitor) treatment was evaluated for their ability to prevent infection of kiwifruit after they were artificially inoculated with Botrytis cinerea or Penicillium expansum. Natural infection of treated fruit was also assessed. As a standalone treatment, C. diversa or harpin significantly reduced gray (B. cinerea) and blue mold (P. expansum) infections on kiwifruit, relative to the untreated control fruit, and also reduced the level of natural infection. The combination of C. diversa and harpin treatment, however, provided a superior level of control on fruit, relative to either treatment alone. Harpin did not negatively impact C. diversa growth in kiwifruit wounds. Treatment of kiwifruit with C. diversa and harpin alone or in combination also induced the activity of enzymes involved in defense response, such as polyphenol oxidase, peroxidase and superoxide dismutase. Harpin alone or in combination with C. diversa enhanced accumulation of lignin content in kiwifruit as well. The mode of action by which harpin enhanced biocontrol efficacy of C. diversa may be partially attributed to the elicitation of defense response in kiwifruit. Integrating the use of antagonistic yeast with harpin treatment has potential as an effective method for the control of postharvest decay in kiwifruit.

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