Preharvest application of ozone in Actinidia chinensis var. chinensis to enhance fruit quality and control postharvest losses caused by Botrytis cinerea

Kiwifruit can be stored in cold conditions for several months without losing sensorial and nutraceutical quality. However, postharvest diseases, such as gray mold (Botrytis cinerea) can cause severe economic damages. Moreover, B. cinerea also causes premature ripening of the healthy fruit by producing ethylene and inducing its biosynthesis in infected fruit, thus amplifying its damages. Current control strategies rely on the use of fungicides during blooming and close to harvest to reduce primary B. cinerea inoculum. Nonetheless, fungicide application often results in an inadequate control due to pathogen resistance to fungicides and to the fact that they are applied prior the picking wound, which is the main infection site. Moreover, fungicide use in these phenological phases is particularly risky both for the potential residues on fruit and the off-target effects on a beneficial insects. All these factors are fostering the research on alternative to synthetic fungicides. The present study investigated the use of pre-harvest application of ozone and ozone emulsified oil to control postharvest incidence of gray mold. Application of O3 at 4 ppm at blooming time reduced natural population of B. cinerea and Pseudomonas syringae pv. actinidiae on flowers up to 97% in the first 6 days. Concerning postharvest, ozone application reduced up to 80% gray mold incidence in comparison to control. Finally, the ozone treatment had not negative effect on any of the fruit quality parameters.