Cell-wall Degrading Enzymes Produced By Phomopsis Longanae Chi. And Its Pathogenicity For Longan Fruit

Phomopsis longanae Chi. is an important pathogenic fungi on latent period in longan fruits. During the process of pathogenicity, it can produce many kinds of enzymes in disease development. A cell-wall degrading enzymes (CWDEs) produced in Phomopsis longanae Chi. was isolated by our laboratoty. Study the cell-wall degrading enzymes (CWDEs) by Phomopsis longanae Chi. and their pathogenicity to longan fruits and the phenolics inhibition for it could make us best understing about pathogenic mechanisms of plant pathogens and control the post-harvest longan fruit diseases.The results were as follows:1、The crude CWDEs produced by Phomopsis longanae Chi. In improved Czaper medium, reserved the supernatant by cultered filtrate was centrifugalled, cellulase (Cx), β-glucosidase (β-G), polygalacturonase (PG) and pectin methylgalactuonase (PMG) were determined in the crude enzymes. The factors including the carbon source, the nitrogen source, the cultural time, the original pH and the cultural temperature were stuied for producing CWDES by Phomopsis longanae Chi. Showed the optimum codition for producing CWDES. Then using the cultural time, the original pH, the carbon source, the nitrogen source to design L16(45) orthogonal experiment and finded the optimal condition of Phomopsis longanae Chi., the results showed that:the cultural time was4d, the original pH was5.0, the optimum carbon source and the nitrogen source were1.5%powder of longan pericarp,0.5%potassinm nitrate. Among the cellulases, β-glucosidase activity was1533.15U/mL which was four point five times of the previous.the pectinases, PG’s activity was more higher with282.31U/mL, was one point five times of the previous.2、The CWDES of Phomopsis longanae Chi. have obvious damage to the cell membrane of longan pericarp. Afrer treated by cellulase, pectinase and mixed enzymes, the osmosis of cytomembrane of longan pericarp increased. The mixed enzymes’lesion rate was48.37%, its damage was the most prominent. The leion rate of cellulase and pectinase were40.43%and34.78%. The CWDE of Phomopsis longanae Chi. have obvious damage to the pericarp tissue of longan fruit. Treated by the enzymes of pectinase, cellulase and mixed enzymes, the longan pericarp tissue were brown and presented macerated. The symptoms of leaves treated with mixed enzymes were more serious than that of longan trested by pectinase and cellulase.After Phomopsis longanae Chi. infected longan fruit, four kinds of CWDEs (Cx, β-glucosidase, PG, PMG) could be examined, and the activity of PG was the highest. However, among different part of diseased longan pericarp the activity of CWDE’s activity was also different. It was found that the CWDE’s activity was the highest around the boundary between diseased and healthy areas. And the next was diseased areas, the last was healthy areas.3、The results of the research showed that lower concentration of pyrocatechol(0.2-0.5mg/L), phloroglucinol(0.2-2mg/L) and anillin(0.2-2mg/L) were all capable to induce Phomopsis longanae Chi. to produce CWDE. And along with the phenolics’concentration increased, CWDE’s production decreased. Pyrocatechol, phloroglucinol and vanillin were all capable to inhibit the producion of CWDE. Their inhibiting concentrations were10mg/L. Pyrocatechol, phloroglucinol and vanillin were all capable to inhibit the activity of Phomopsis longanae Chi. CWDE. Vanillin showed the strongest inhibiting ability, when its concentration was10mM, the four kinds of enzymes (Cx, β-glucosidase, PG, PMG) were all inhibited. Pyrocatechol and phloroglucinol were the next, inhibiting concentration were200mM and500mM.