Effects of postharvest oligochitosan treatment on anthracnose disease in citrus (Citrus sinensis L. Osbeck) fruit

Citrus fruit (Citrus sinensis L. Osbeck) is susceptible to infection by Colletotrichum gloeosporioides during poststorage, which rapidly decreases sensory and nutritional quality of the fruit. The ability of oligochitosan treatment to control C. gloeosporioides of citrus fruit during storage was examined, and possible underlying mechanisms were discussed. Disease incidence and lesion diameter were lower in oligochitosan-treated fruits compared with their respective controls. The fruits dipped in oligochitosan showed increased contents of lignin, hydroxyproline-rich glycoprotein (HRGP), hydrogen peroxide (H2O2), ascorbate, glutathione, total phenol, and flavonoid compounds. In addition, enzymatic activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), polyphenoloxidase (PPO, EC 1.14.18.1), ascorbate peroxidase (APX, EC 1.11.1.11), and beta-1, 3-glucanase (GLU, EC 3.2.1.39) also increased in citrus fruit peels, all of which were correlated with the onset of induced disease resistance. These results indicated that oligochitosan treatment can induce disease resistance of citrus fruit to C. gloeosporioides Penz. Oligochitosan can be a potential alternative to conventional control methods of postharvest anthracnose in citrus fruit.