Postharvest Application of Oligochitosan and Chitosan Reduces Calyx Alterations of Citrus Fruit Induced by Ethephon Degreening Treatment

In the present study, we investigated whether the postharvest application of oligochitosan and chitosan could be used as potential alternatives to 2,4-dichlorophenoxyacetic acid (2,4-D) treatment to prevent calyx senescence of mandarin fruits induced by degreening treatment. The results of scanning electron microscopy indicated that the ethephon degreening treatment could accelerate the formation of pedicel abscission layers. Treatments with 15 g kg(-1) oligochitosan, 5 g chitosan, and 50 mg kg(-1) 2,4-D significantly suppressed the formation of pedicel abscission layers of ethephon degreening fruit and inhibited the browning of the calyx. These two treatments delayed the degradation of protopectin, cellulose, and lignin. Inhibition of the increase in the abscisic acid (ABA) content was also observed in these two treatments. In conclusion, these two treatments, particularly 15 g kg(-1) oligochitosan, could be potentially used as alternatives to 2,4-D to improve calyx alterations induced by the ethephon degreening treatment in mandarin fruits.