A Ntifungal Activity And Mechanism Of Sodium Copper Chlorophyllin Against Valsa Mali

Valsa mali is the most common disease in apple cultivation.It is widely distributed in China and has a large harm area.Studies have shown that sodium copper chlorophyllin,as a chlorophyll-derived compound,has good antifungal activity,is environmentally friendly and non-toxic,but it is still in the preliminary research stage.Based on the related research,this paper conducts further experimental research on the antifungal activity,stability and antifungal mechanism of sodium copper chlorophyllin.The main results are shown as followed:(1)Sodium copper chlorophyllin had different inhibitory effects on five plant pathogens(Valsa mali、Pestalotia shiraiama、Botrytis cinerea、Colletotrichum orbiculare、Cytospora chrysosperma),and the antifungal effects increased with increasing concentration.Among them,sodium copper chlorophyllin showed the most significant inhibitory effect on V.mali(P<0.05).At a concentration of 20 mg/mL,sodium copper chlorophyllin inhibited the radial growth of V.mali by up to 100%both under light and dark conditions.The EC50 of sodium copper chlorophyllin test solution was 7.405 mg/mL and 6.959 mg/mL under light and dark conditions,respectively.The dry weight of mycelium decreased with increasing concentration.When the concentration was 10 mg/mL,inhibition rate was up to 100%and the dry weight of mycelium was only 5 mg/200mL.(2)The stability test results showed that it had no significant effect on different physical and chemical conditions of the antifungal activity of sodium copper chlorophyllin.Among them,effect of temperature on the inhibition rate increased first and then decreased,stable under 70℃(P>0.05);Inhibition rate decreased with increasing acidity under acidic conditions,under alkaline conditions inhibition rate substantially unchanged(P>0.05);The effects of different UV irradiation time and redox agent on the inhibition rate were not significant(P>0.05).(3)Sodium copper chlorophyllin had an effect on the activity of six enzymes related to the growth and metabolism of V.mali.It can effectively activate defense enzymes of V.mali(T-SOD,POD,PPO and CAT),and can also inhibit cell wall degrading enzymes.CL and Chitinase were significantly inhibited to varying degrees(P<0.05),the inhibition rate of CL on the 3rd day was 68.24%,and the inhibition rate of Chitinase on the 5th day reached 65.59%.(4)Sodium copper chlorophyllin had a significant effect on the cell membrane of V.mali.The membrane permeability of mycelium treated with sodium copper chlorophyllin was significantly enhanced,resulting in the conductivity of the culture medium at various time points,and the content of MDA in mycelium significantly exceeded(P<0.05).Among them,at the 3rd day,the conductivity of the treatment group reached 1463 μs/cm,which was 1.4 times than that of the control.The MDA content was 41.25 μmol/L at the 4th day,which was 2.6 times than that of the control.Moreover,sodium copper chlorophyllin had a destructive effect on cell wall structure.Adding sorbitol for the fungi test proved that the cell wall of V.mali was damaged.The results of the scanning microscopic observation of the hyphae of V mali showed that sodium copper chlorophyllin caused the mycelia to grow abnormally,swell,grow weak and blur the outline.