Study On The Prevention And Control Of Copper Sulfate And Geraniol On Geotrichum Citri-aurantii

Citrus sour rot is the third largest fungal disease in Citrus postharvest diseases after penicilliosis and green mold.There are few kinds of special fungicides,and there are problems such as pesticide residues and threats to human health.Therefore,it is necessary to find safe and effective alternative measures.In this paper,the control effect of copper sulfate and geraniol on Geotrichum citri-aurantii was investigated.The main results are as follows:1.Control effect of copper sulfate and geraniol on G.citri-aurantii.Using hyphal growth method to study the inhibitory effect of copper sulfate and geraniol with different concentrations on G.citri-aurantii,it was found that both could effectively inhibit the occurrence of G.citri-aurantii.The minimum inhibitory concentration(MIC)of copper sulfate and geraniol were 0.7 g/L and 0.5 g/L.The germination rate of spores under the minimum inhibitory concentration(MIC)of copper sulfate and geraniol were 2.21% and3.28%,which effectively inhibited the spore germination of G.citri-aurantii.Electron microscopy found that copper sulfate and geraniol treatment with minimum inhibitory concentration(MIC)destroyed the integrity of G.citri-aurantii cells,the hyphae was deformed,the cell wall and the cell membrane were separated,the organelles disappeared,and the cells showed vacuolization.The permeability of the cells was altered,the AKP and nucleic acid were released,conductivity was increased,membrane lipid peroxidation was enhanced,and reactive oxygen species were accumulated.2.Control effect of copper sulfate and geraniol on G.citri-aurantii in vivo.Different concentrations of copper sulfate and geraniol were mixed with G.citri-aurantii spore suspension to inoculate on the fruit surface.It was found that when the concentration was 10 times of the minimum inhibitory concentration(10×MIC),they could significantly inhibit the occurrence of G.citri-aurantii,and the onset time of both were later than that of the control group,and the lesion diameters were significantly lower than that of the control group.One week after inoculation,the lesion diameters of the control group were 39.99 mm,and the lesion diameters were only 28.47 mm and 28.33 mm under copper sulfate and geraniol.3.Effects of copper sulfate and geraniol on fruit-related enzymes.After treatment of citrus fruits with copper sulfate and geraniol,catalase(CAT)activities were as high as150.29 U/g and 164.43 U/g,polyphenol oxidase(PPO)activities were 43.78 U/g and30.89 U/g,phenylalanine ammonia lyase(PAL)activities were 98.22 U/g and 105.28 U/g,but the effect on peroxidase(POD)was not obvious.In conclusion,the prevention and control effect of copper sulfate and geraniol on G.citri-aurantii laid a theoretical foundation for the study of Citrus sour rot,and also provided a new measure for the control of Citrus sour rot.