Study On The Antibacterial Mechanism Of Sodium Pheophorbide(SPA) On Botrytis Cinerea

Botrytis cinerea is an important plant disease in the world.SPA is a water-soluble sodium salt of chlorophyll derivative pheophorbide a.It is an environment-friendly,pollution-free,plant-derived compound with significant antibacterial,insecticidal,antiviral and antitumor activities.SPA was applied to plant diseases,and its antibacterial activity and mechanism against B.cinerea were studied.It has certain significance for the control of B.cinerea and the development of photoactivated pesticides.In this study,the antibacterial effect of SPA on B.cinerea in vitro and in vivo were studied.The effects of SPA on the mycelial structure and related enzyme activities of B.cinerea were studied.The results are as follows:(1)Under light and dark conditions,SPA had inhibitory effect on mycelial growth and spore gennination of B.cinerea,and the inhibitory effect increased with the increase of the concentration of the solution.The inhibitory effect of SPA at the same concentration was also significantly different(P<0.05).When the concentration of SPA was 20 mg/mL,the inhibition rates of mycelial growth and spore germination were 71.77%and 72.05%,respectively.The EC50 of SPA on mycelial growth was 9.77 mg/mL and 17.39 mg/mL in dark.When the concentration of SPA was 10 mg/mL,the dry weight of mycelia was only 5.77%of the control.(2)SPA has a significant effect on the cell structure of B.cinerea.The cell membrane permeability of the mycelium of B.cinerea treated with SPA was significantly enhanced,resulting in a significantly higher culture medium conductivity,MDA content and sodium potassium ATPase activity of B.cinerea than the control group(P<0.05).Moreover,SPA has a destructive effect on the structure of the cell wall.The addition of sorbitol for antifungal test proved that the cell wall of B.cinerea mycelium was destroyed,and the destruction of the cell wall resulted in 1 mg/mL treatment group alkaline phosphatase The activity was significantly higher than that of the control group(P<0.05);from the observation results of the mycelial microstructure,it can be seen that SPA caused the hyphae to appear weak,fuzzy outline and cell wall dissolution.(3)SPA can effectively inhibit the activities of protective enzymes,cell wall degrading enzymes and TCA-related enzymes in the mycelium of B.cinerea,and the cell wall degrading enzymes SOD,POD,CAT,and TCA after being treated with SPA,The activities of SOD,POD,CAT,EG,PL,PG,ICDHc,a-KGDH,NAD-MDH,SDH,and CS in the treatment group were significantly lower than those in the control group(P<0.05),indicating that SPA reduced the mycelial viability.The growth of mycelium played an inhibitory role.The PL activity of the 1mg/mL treatment group was only 10.74%of the enzyme activity of the control group;the ICDHc activity of the 1mg/mL treatment group was only 2.39%of the enzyme activity of the control group;the NAD-MDH activity of the 1mg/mL treatment group was only that of the enzyme activity of the control group 6.87%.