Effects of Post-harvest Applications of Oligochitosan and Chitosan on the Quality and Resistance of Ethephon-degreened Citrus Fruit to Disease
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Abstract:
The effects of 1.50% oligochitosan and 0.50% chitosan treatments on the control of stem-end rot and fruit water loss caused by ethephon degreening and indices related to basic fruit storage and disease resistance were assessed using 2,4-dichlorophenoxyacetic acid (2,4-D) treatment as a positive control. The results indicated that external ethylene, 50.00 mg/kg 2,4-D, 1.50% oligochitosan, and 0.50% chitosan treatments had no significant adverse effects on the storage quality of citrus fruits. However, 1.50% oligochitosan and 0.50% chitosan were superior to 2,4-D to reduce fruit weight loss caused by ethylene degreening. Treatment with 1.50% oligochitosan significantly increased the activity of polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia-lyase (PAL), and β-1,3-glucanase (GLU). Furthermore, it improved the total phenolic and flavonoid content in the peel of ethephon-degreened citrus fruit and increased the activity of chitinase (CHI) to a certain extent. Treatment with 0.50% chitosan also significantly increased the PPO, POD, PAL, CHI, and GLU activities, and although not significant, it appeared to improve the total phenolic and flavonoid contents. In contrast, 50.00 mg/kg 2,4-D treatment only caused significant inductions of POD and PAL activities in the peel, but had limited effects to increase the activity of PPO and GLU as well as total phenolic and flavonoid content. In conclusion, oligochitosan and chitosan are potentially valuable to replace 2,4-D for commercial post-harvest citrus degreening.
