Abstract:

【Objective】 The effects of chitosan treatment on the disease resistance, the content of salicylic acid (SA) and the active oxygen metabolism of navel orange fruit (Citrus sinensis L. Osbeck) cv. Newhall were investigated 【Method】 After harvest, navel orange fruits were treated with 2% chitosan solution for 1 min in different days. The influences of chitosan treatment on the disease resistance of navel orange to Penicillium italicum, the content of SA content and materials related to active oxygen metabolism in navel orange’s peel were detected. 【Result】 The inoculated disease incidence and the expansion of lesion diameter of navel orange were significantly reduced by 2% in chitosan treatment (P＜0.01), and fruits dipped into 2% chitosan 2 days before inoculation shown the most significant effect. Two percent treatment effectively enhanced the activities of peroxidase (POD), glutathione reductase (GR) and the levels of free SA and hydrogen peroxide (H2O2), while inhibited the activities of catalase (CAT), ascorbate peroxidase (APX) and the decreased the ascorbate (AsA) content. Besides, the accumulation of glutathione (GSH) was sharply induced in the early time after treatment. 【Conclusion】 Two percent chitosan treatment could induce the disease resistance of Navel orange to the infection of Penicillium italicum, and these resistance reactions relate to the regulation of the content of SA, the levels of active oxygen metabolism and the changes of antioxidant enzymes.

Key words: chitosan, navel orange, reactive oxygen metabolism, salicylic acid, disease resistance