UV-B alleviates postharvest chilling injury of zucchini fruit associated with a reduction in oxidative stress

Cold storage is widely used to preserve the physical and chemical qualities of fresh fruit and vegetables. However, some tropical and subtropical fruit are very sensitive to cold, exhibiting external and internal chilling injury (CI) symptoms when stored at low temperatures. In this study, we analyze the effect of UV-B irradiation on chilling injury and oxidative stress of zucchini fruit (Cucurbita pepo) from three hybrid cultivars that differ in their sensitivity to CI. Fruit with an average length of 20 cm was irradiated with 1.1 W m(-2) of UV-B for 4 hours before storage for 7 days at 4degree celsius. The fruit of the three cultivars responded positively to UV-B, significantly reducing the CI index, weight and firmness loss, H2O2 content, and membrane damage during cold storage. The fruit exposed to UV-B also exhibited higher levels of flavonoid content and antioxidant capacity, which correlated with a significant reduction in cold damage between cultivars and treatments. The expression of CpNCED1, a key gene in the ABA biosynthesis pathway, increased in response to cold stress and UV-B treatment, suggesting that ABA could mediate the response to UV-B. Taken together, the results indicate that postharvest UV-B irradiation of zucchini fruit enhances chilling tolerance by triggering an increase in flavonoid accumulation and antioxidant capacity, and therefore reducing the oxidative stress generated during fruit storage at low temperature.