Effect of Chitosan Combined with Sodium Silicate on Phenylpropanoid Metabolism and Pathogenesis-Related Proteins of Postharvest Winter Jujube

The effects of chitosan combined with sodium silicate treatment on phenylpropanoid metabolism and defense-related enzymes of postharvest winter jujube inoculated with A. alternata. Winter jujube was treated 1% CTS combined with different concentrations (10, 40, 160 mmol/L) of Na₂SiO₃ for 5 min and stored at room temperature, distilled water treatment was used as control. All physiological indexes such as the lesion diameter, flavonoids, polyphenols, lignin and related enzymes were measured. After 20 d of incubation, the lesion diameters on jujube treated with 1% CTS+40 mmol/L Na₂SiO₃ was 57.33% of the lesion diameters of 1% CTS treatment. Moreover, 1% CTS+40 mmol/L Na₂SiO₃ treatment promoted the accumulation of total phenolics, flavonoids and lignin in fruit which due to stimulate the activities of phenylalanine ammonialyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate CoA ligase (4CL) and peroxidase (POD). 1% CTS+40 mmol/L Na₂SiO₃ treatment also increased the activities of chitinase (CHT) and β-1, 3-glucanase (GLU) which play a significant role in the pathogenesis-related proteins. These results suggested that CTS+Na₂SiO₃ treatment could decrease A. alternata rot and induce disease resistance of winter jujube through enhancing phenylpropanoid metabolism and pathogenesis-related proteins production.