Study On The Activity Of Three Plant-derived Volatile Components Against Tea Tree Anthracnos

Anthracnose of tea plant occurs widely in tea plantation,which has great influence on the growth of tea plant,quality and yield of tea.With the development of modern agriculture and the deepening of the concept of sustainable development,the country vigorously advocates the reduction of chemical pesticide application,and it is necessary to seek more safe and effective control measures to reduce or replace chemical agents in production.Plant volatile components are the focus of plant disease control research,which has the characteristics of low residue and environmental friendliness.Based on the chemical ecology strategy of tea plant disease,In this study,the species of anthracnose were successfully isolated and identified,and the antibacterial activities of geraniol,citronellol and citral were determined.In this study,the species of anthracnose were successfully isolated and identified,and the antibacterial activities of geraniol,citronellol and citral were determined.The activity and content changes of enzymes related to anthracnose were detected by the kit,and the inhibitory mechanism of three volatile components on anthracnose of tea was initially explored.The main results are as follows.1.Successfully isolated and identified the pathogen of tea anthracnose and identified its biological characteristics.According to Koch’s rule,single sporulation isolation,morphology and polygene identification（ITS,GAPDH,ACT and CHS-1）were used to isolate and identify the pathogens of 50 typical leaf specimens of anthracnose from 13 tea areas in Guizhou Province.Three pathogens were identified,namely Colletotrichum camelliae,Colletotrichum fructicola and Colletotrichum jiangxiense,with the isolation frequencies of 64%,2%and 2%,respectively.The optimal medium for the three pathogens was PDA,the optimal p H was 6,the optimal nitrogen source was peptone,and the optimal carbon source was maltose,glucose and maltose,respectively.The results showed that C.camelliae was the dominant pathogen of anthracnose in tea area of Guizhou Province.2.The antibacterial activities of geraniol,citronellol and citral against C.camelliae were studied.The bacteriostatic activities of geraniol,citronellol and citral against mycelia and spores were studied by growth rate method and water agar culture method.The results indicated that the inhibition rates of mycelium at 0.25 mg·m L^-1reach 48.9%,60.9%and 66.5%,respectively.At the concentration of 1-0.125mg·m L^-1,the inhibition rate of conidia was higher than 85%.The results indicated that the inhibition rate of mycelia and conidial germination was positively correlated with their concentration.The inhibition effect of citral on C.camelliae was superior to geraniol and citronellol.The MIC values of geraniol,citronellol and citral against C.camelliae were 0.5,0.5 and 0.25 mg·m L^-1,respectively.The MBC values were 1,1and 0.5 mg·m L^-1,respectively.The results showed that all three substances showed good antibacterial activity against C.camelliae,and citral indicated the excellent antibacterial activity.3.The effects of geraniol,citronellol and citral on the mycelia and intracellular structure of C.camelliae were studied.The effects of geranol,citronellol and citral on the mycelia and cell structure of C.camelliae were explored by optical microscopy（OM）,scanning electron microscopy（SEM）and transmission electron microscopy（TEM）.The OM and SEM results showed that the mycelial surface were wrinkled with different degrees of folding,distortion and cross fracture,and the cell surface structure was seriously damaged in the MBC concentration treatment group.The TEM results showed that the mycelial were treated,the integrity of the cell membrane structure of the bacteria was damaged,the endoplasmic dissolution was dissolved,the bacteria spilt or burst,and some signs of atrophy were observed.The results suggest that geraniol,citronellol and citral may interfere with cell energy metabolism by acting on cell membrane and cell wall.4.The effects of geraniol,citronellol and citral on C.camelliae related enzymes were studied.The activity and content of 7 enzymes of C.camelliae were detected by the kit.The cellulase activity,malondialdehyde（MDA）content,soluble protein content,peroxidase（POD）and superoxide dismutase（SOD）activities,succinate dehydrogenase（SDH）and malate dehydrogenase（MDH）activities of the pathogen were increased after the three volatile components were treated.According to the results,the three components can decompose the cellulose on the cell wall by enhancing the activity of cellulase of this bacterium,and damage the cell wall structure.By reducing the activities of POD and SOD,the content of soluble protein is decreased,and the content of MDA is increased.By reducing the activities of SDH and MDH,the metabolism of mitochondria is affected,the tricarboxylic acid cycle is interfered,and the normal growth of bacteria is inhibited.In this study,C.camelliae,C.fructicola and C.jiangxiense were successfully separated and identified by monospora isolation,morphological observation and molecular analysis.The effects of geraniol,citronellol and citral on the bacteriostatic activity,mycelium and cell structure of C.camelliae were studied,and the bacteriostatic mechanism of C.camelliae was preliminarily clarified.The results provided basic reference for the further study on the antibacterial action of C.camelliae and the control of tea anthracnose.