Study On The Inhibition Of Monochromatic Visible Light On Citrus Sour Rot Pathogen

In order to investigate the effect of visible light on the growth and infection of Geotrichum citri-aurantii,red light?670 nm?and blue light?450 nm-460 nm?were used to irradiate G.citri-aurantii colony and citrus fruit inoculated with G.citri-aurantii.The optimum light intensities and illumination time condition of inhibition G.citri-aurantii was determined.On this basis,we determined the content of reactive oxygen species and antioxidant enzymes activities to know the effects of blue light on the defense system of citrus fruits,and also determined the quality of citrus.Through screening G.citri-aurantii mutants,we obtained mutant 22-3 and analyzed its physiological biochemical and pathogenicity for providing a theoretical basis for the prevention and treatment of postharvest diseases of citrus using visible light in the future.The main findings are as follows:1.In vitro,both red light and blue light could inhibit the growth of G.citri-aurantii,and illumination time which were 24 LL had better antibacterial effects.Blue light were higher than red light at the same photoperiod,while the inhibition rate of red light is only 16.2%of blue light.Geotrichum citri-aurantii had no growth with the blue light intensity of 200±10?mol m^-2 s^-1.In vivo,blue light significantly reduced decay caused by G.citri-aurantii on‘Guoqing 1'mandarin?Citrus unshiu?fruit and Citrus reticulata Blanco cv.Ponkan.2.Blue light could improve activities of SOD in citrus fruit,but no effect on CAT and POD,and could not decrease the content of O₂^-and H₂O₂.Therefore,blue light could inhibit the infection mainly by inhibiting the growth of G.citri-aurantii.In addition,blue light has no effect on the content of SSC,TA and Vc.3.Compare the difference between strain 22-3 and wild strains.?1?The growth of strain 22-3 were slower than wild strains,and the amount of sporulation of wild bacteria was 2.5 times that of strains 22-3.?2?There was no difference in the growth of strain 22-3 and wild strains with treatmenting of 20?-30?,but strain 22-3 could grow in 37?while wild strains not.?3?The effect of pH on the growth of strains22-3 and wild strains was not significant,and were better in neutral alkalinity.?4?Strains 22-3 was more resistant and grew better than wild strains to various stress treatments.?6?There was no significant differences of disease incidence and surface pH of citrus fruit after inoculation strains 22-3 and wild strains.