Research advance on nitric oxide inhibiting diseases in fruits and vegetables

Abstract: Nitric oxide(NO), as an important signal molecule, has been reported to play a very important role in postharvest ripening and disease resistance in fruits and vegetables. Postharvest diseases are the important cause of postharvest loss of fruits and vegetables. There are physiological diseases and infectious diseases. Chemical reagents are generally used to treat the postharvest fruits and vegetables for disease control, but this may cause harmful effects on human health. The application of exogenous NO has been reported to induce disease resistance in postharvest fruits and vegetables, which provides a sustainable and safe approach in the control of postharvest decay. The quality of postharvest fruits and vegetables is related to respiratory intensity, VC content, moisture content, soluble solids and hardness. Exogenous NO treatment is effective to inhibit the respiration rate and chlorophyll degradation in fruits and vegetables, delay the decline of VC, soluble solids and hardness, and reduce the loss of water.Therefore, the commodity and edible values of fruits and vegetables are well maintained. Low-temperature storage is widely practiced to control the quality deterioration of various plant products. It reduces the rate of cell metabolism and delays the process of ripening and senescence. However, some tropical or subtropical fruits and vegetables are susceptible to chilling injury. NO treatment inhibits the occurrence of chilling injury in postharvest fruits and vegetables such as peaches, bananas, cucumbers and tomatoes. Researchers have revealed the mechanism of NO inducing chilling tolerance of postharvest fruits and vegetables through active oxygen metabolism, proline metabolism, energy metabolism and membrane lipid metabolism. NO also induces chilling tolerance by regulating the expression of related genes. The CBF anti-cold pathway is considered to be the most critical and well-researched pathway for cold response in plants, and the CBF genes are the hub of this pathway. The CBF genes may play an upstream role in regulating the expression of downstream cold-tolerant genes, thus increasing the tolerance of plants to low temperatures. Pathogens are the main cause of infectious diseases in postharvest fruits and vegetables, and the infectious diseases of fruits are almost all caused by fungi, while the decay of leafy vegetables is chiefly caused by bacteria. Major infectious diseases include anthracnose,botrytis cinerea, brown rot disease and so on. Inhibition of different diseases usually requires the use of different types of fungicides, and more efficient antimicrobial methods are highly desired. Plant induced resistance refers to the use of inducing factors to induce plant disease resistance, which can protect fruits from pathogen for a long time and has the advantage of being environmentally friendly. Inducing factors include physical, chemical and biological factors. The mechanism of different inducing factors is different. NO as a chemical factor has been reported to induce the disease resistance in postharvest fruits and vegetables. NO promotes the synthesis and accumulation of secondary metabolites in fruit and vegetable cells by inducing the activities of phenylpropanoid metabolism-related enzymes and disease-resistant related proteins, which inhibit the infection of pathogen. The research on NO inhibiting the diseases in fruits and vegetables has attracted increasing attention. In the future, the achievement from these studies may be applied to practice.