Abstract:

Citrus fruits were treated for 10 min with propolis extract dissolved in a small amount of absolute ethanol and diluted with water to a concentration of 0.1%, inoculated with Penicillium italicum suspension (1 × 106 CFU/mL) at different posttreatment time points and stored at 26 ℃. After 72 h storage, the inhibitory effect of propolis extract treatment against lesion diameter of citrus fruits inoculated with Penicillium italicum was measured to determine the optimal expression time for resistance to blue mold disease. Besides, the changes in biochemical and physiological parameters of treated citrus fruits were examined. Results showed that treated citrus fruits exhibited the strongest resistance to blue mold disease at 48 h post-treatment. Propolis extract treatment increased the content of total phenolic compounds and enhanced the activities of enzymes related to induced disease resistance such as phenylalanine ammonia-lyase, polyphenol oxidase, peroxidase, and chitinase in citrus fruit peels. This demonstrates that propolis extract treatment has the ability to strengthen the defense system and reduce the blue mold disease incidence in citrus fruits, thereby providing an effective approach for the fresh-keeping of citrus fruits.

Key words: propolis extract, citrus fruit, disease resistance, blue mold