Chitosan coating enriched with biosynthetic CuO NPs: Effects on postharvest decay and quality of mango fruit.

A chitosan-based nanocomposite film (CSC) was developed by mixing chitosan (CS, 2 %, v/v) and copper oxide nanoparticles (CuO NPs, 500 µg∙mL-1) synthesized using Alpinia officinarum extract for the safe storage of mango fruit. The effects of CuO NPs on the morphological, mechanical, thermal, physical and antifungal properties of the CS films and postharvest quality of mango fruit were determined. Scanning electron microscopy (SEM) analysis confirmed that CuO NPs were uniformly dispersed into the CS matrix. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) profiles showed that intermolecular H-bondings occurred between CS and CuO NPs, accompanied by decreased crystallinity and increased amorphous structure. In comparison to the pure CS film, addition of CuO NPs obviously improved the morphological, mechanical, thermal, physical and antifungal properties of CSC film. CSC coating treatment obviously delayed the fruit decay and yellowing, as well as reduced losses of weight and firmness of mango (Mangifera indica L.) fruit during the storage, when compared with the control and CS coating treatment. Meanwhile, it significantly decreased the respiration rate and ethylene generation and maintained high level of ascorbic acid (AsA), titratable acid (TA) and soluble sugar content (SSC) of the fruit during the storage. Notably, Cu presented in the CSC film was restrained to the peel, indicating that the CSC coated mango fruit had good edible safety. Principal component analysis (PCA) confirmed that CSC coating played a positive role in mango preservation. Therefore, CSC coating can be considered a potential application for successfully controlling of postharvest disease and prolonging the shelf life for mango fruit.

Putrescine (1,4-Diaminobutane) enhances antifungal activity in postharvest mango fruit against Colletotrichum gloeosporioides through direct fungicidal and induced resistance mechanisms.

Anthracnose decay caused by Colletotrichum gloeosporioides greatly shortens the shelf life and commercial quality of mango fruit. Putrescine (1,4-Diaminobutane) is involved in modulating plant defense to various environmental stresses. In this research, in vivo and in vitro tests were used to explore the antifungal activity and the underlying mechanism of putrescine against C. gloeosporioides in mango fruit after harvested. In vivo tests suggested that putrescine markedly delayed the occurrence of disease and limited the spots expansion on inoculated mango fruit. Further analysis exhibited that putrescine treatment enhanced disease resistance, along with enhanced activities of chitinase (CHI), ß-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumarate coenzyme A ligase (4CL), polyphenol oxidase (PPO) and the accumulation of lignin, flavonoid, phenolics, and anthocyanin in infected mango fruit. In addition, in vitro tests showed that putrescine exerted strongly antifungal activity against C. gloeosporioides. Putrescine induced the production of reactive oxygen species (ROS) and severe lipid peroxidation damage in C. gloeosporioides mycelia, resulting in the leakage of soluble protein, soluble sugar, nucleic acids, K+ and Ca2+ of C. gloeosporioides mycelia. The mycelium treated with putrescine showed severe deformity and shrinkage, and even cracking. Taken together, putrescine could effectively reduce the incidence rate and severity of anthracnose disease possibly through direct fungicidal effect and indirect induced resistance mechanism, thus showing great potential to be applied to disease control.

Exogenous Nitric Oxide-Induced Postharvest Gray Spot Disease Resistance in Loquat Fruit and Its Possible Mechanism of Action.

The effectiveness of nitric oxide (NO) for control of grey spot rot cause by Pestalotiopsis eriobotryfolia in harvested loquat fruit and its probable mechanisms have been investigated. The results showed that NO donor sodium nitroprusside (SNP) did not evidently inhibit mycelial growth and spore germination of P. eriobotryfolia, but resulted in a low disease incidence and small lesion diameter. SNP resulted in a higher hydrogen peroxide (H2O2) level in the early stage after inoculation and a lower H2O2 level in the latter period by regulating the activities of superoxide dismutase, ascorbate peroxidase and catalase. At the same time, SNP enhanced the activities of chitinase, ß-1,3-glucanase, phenylalanine ammonialyase, polyphenoloxidase, and total phenolic content in loquat fruit. However, SNP treatment inhibited the activities of cell wall-modifying enzymes and the modification of cell wall components. Our results suggested that NO treatment might have potential in reducing grey spot rot of postharvest loquat fruit.