Effects And Metabolisms Of NO On Storage And Disease Resistance Against Blue Mold Of Navel Oranges

The effects of exogenous Nitric Oxide treatment(fumigate with 15μl L-1NO gas)on preservation and disease resistance of Newhall navel oranges were investigated,and the physiological bases of enhancing storage quality and disease resistance by NO treatment of navel oranges were also discussed.The main results were as follows:1.NO treatment effectively reduced the weight loss of navel oranges stored at 5℃and 20℃,keeped SSC content,and delayed the decrease of TA and Vc content.Compared with chemical fungicide prochloraz and control,the treatment with NO significantly improved the storage quality of navel oranges.NO treatment also significantly inhibited the developments of natural infection rate and lesion areas of postharvest navel oranges during storage.2.Fumigation with NO could affect active oxygen metabolism by maintaing higher SOD and CAT activities,reducing 02·-production rate and H2O2 content,raising the antioxidant capacities and inhibiting the accumulation of ROS.Thereby,NO delayed fruit repening and senescence,and prolonged the storage life of navel oranges.At the same time,NO treatment also significantly enhanced defense enzymes activities such as PPO,POD and PAL,and promoted the synthesis and accumulation of pathogenesis-related proteins such as GLU and CHT.Thus NO improved the ability of navel oranges stored at 5℃ against blue mould,and reduced the occurrence of disease.3.NO fumigation treatment significantly reduced the incidence of inoculated navel oranges,delayed the extension of the lesion areas and effiectively inhibit the occurrence of blue mold.NO significantly improved SOD and CAT activities,enhanced antioxidant capacities and inhibited CAT activities of navel oranges inoculated with Penicillium italicum,thus affecting the metabolism of active oxygen.In addition,pathogenesis-related proteins such as GLU and CHT also accumulated rapidly.The key enzymes activities of phenylpropane metabolism including PAL,4CL,C4H and CHI were significantly enhanced and the metabolites of total phenolics,flavonoids and lignin were also increased.Therefore,NO treatment affected the active oxygen metabolism,promoted the accumulation of pathogenesis-related proteins and activated the phenylpropane metabolism of navel oranges.As a result,NO treatment improved the disease resistance against blue mould of navel oranges.In conclusion,by influencing active oxygen metabolism,antioxidant capacity,disease defense enzymes activities and phenylpropane metabolism pathway,NO treatment not only improved disease resistance against blue mold,but also maintained the storage quality of navel oranges.