Dynamic Degradation of Penconazole and Its Effect on Antioxidant Enzyme Activity and Malondialdehyde Content in Apple Fruit

The fungicide penconazole is often applied to prevent fungal diseases and improve fruit quality and yield in apple production. However, the impact of penconazole on apple quality and safety remains largely unknown. Here, an efficient detection method of penconazole was developed based on ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and the degradation behaviors of penconazole in Fuji apple fruit were also investigated under both bagging and non-bagging conditions. The results showed that the half-life time of penconazole in apple fruit was 21.8 and 17.5 days under bagging and non-bagging conditions, respectively, and bagging resulted in enrichment of penconazole at the 2nd day. However, there was no significant statistical difference in penconazole residue after 45 days, when the penconazole residue was <= 0.2 mg/L. Beside, there were significant correlations between penconazole residue and superoxide dismutase, peroxidase and malondialdehyde during the degradation of penconazole. These results indicated that penconazole application could induce stress, and bagging affects the activity of antioxidant enzymes in apple fruit. Specifically, penconazole degradation exhibited significant positive correlations with both peroxidase and superoxide dismutase (P < 0.05), but a negative correlation with malondialdehyde (P < 0.01). The findings of the present study provide important implications for the application of fungicides in apple production so as to reduce the health risks to apple consumers and apple producers.