Study On The Antibacterial Components Of Citronella Oil Against Tea Cake Pathogens And Its Tea Stem Porous Carbon Controlled Release Agen

Tea blister blight disease is one of the most serious leaf diseases in tea planting,which seriously affects the quality and yield of tea leaves.Under the background of reducing the application of chemical pesticides and increasing the efficiency,one of the effective ways to achieve the safe and effective prevention and control of Tea blister blight disease is to seek biologically active substances from natural compounds to replace chemical pesticides.Citronella oil derived from citronella has a broad-spectrum antibacterial effect and has the potential to be developed as a botanical pesticide;however,its volatile properties limit its further development and utilization.Therefore,on the basis of the successful isolation of the pathogenic bacteria of Tea blister blight disease,this study determined the activity of related components in citronella oil against the bacteria by measuring the antibacterial activity.Controlled release agent,the controlled release bactericidal activity of the preparation was studied,and the antibacterial mechanism of this ingredient against Tea blister blight disease bacteria was preliminarily studied.Below are key research findings.1.The pathogenic bacteria of Tea blister blight disease that can be preserved and subcultured for a long time were successfully isolated.The improved spore shot method was established,and the study on the isolation of Tea blister blight disease pathogen Exobasidium vexan was carried out.The isolated strain cbb was identified.Combined with the morphological observation,molecular identification and the results of the pathogenicity of the isolated tea leaves,the strain cbb was determined to be E.vexans.Compared with the traditional spore shot separation method,the separation and purification rate is increased by 1.5 times.The established new separation method solves the problem that E.vexans grows slowly on the medium and is not easy to isolate and obtain purified strains.2.The study clarified the main antibacterial components of citronella oil on Tea blister blight bacteria.Five components of citronella oil were screened,and the results of the initial screening by the zone of inhibition showed that geraniol,citral and citronellol reached a high sensitivity level under the test concentration of 5 mg·m L^-1.Using the test tube half-dilution method,the activity of the three substances against the bacteria was further tested.One day after treatment,the MIC values of geraniol,citral and citronellol were 1.25 mg·m L^-1and 0.321 mg·m L^-1,respectively.m L^-1and0.625 mg·m L^-1;MBC were 1.25 mg·m L^-1,0.625 mg·m L^-1and 1.25 mg·m L^-1,respectively.The results showed that citral had the best inhibitory activity against this bacteria in citronella oil.3.The tea stem porous carbon controlled-release agent with the main antibacterial component citral was successfully prepared,and its slow-release bactericidal activity against E.vexans was clarified.Porous carbon materials（BC）with high specific surface area(1001.6 m²·g^-1)and abundant mesoporous structure were prepared by carbonization activation method using tea stems as substrate materials.A novel porous carbon controlled release agent BC@Eo was successfully prepared by loading citral（Eo）on BC using a one-pot method.Fourier transform infrared spectroscopy and X-ray powder diffraction characterization results show that in BC@Eo,BC and Eo undergo chemical and physical interactions.On the 30th day of the sustained-release assay,the cumulative release rate of Eo in BC@Eo in vitro was 51%,while the cumulative release rate of free Eo on the 7th day was 82%.The results showed that BC could effectively control the release of Eo.The inhibition zone of BC,Eo and BC@Eo was 0,19.66±0.79 and 21.92±0.77 mm,respectively,on the7th day of the activity measurement by the inhibition zone method.30 days after BC@Eo treatment of E.vexans,scanning electron microscopy showed that the degree of hyphal folds of BC@Eo treatment was more obvious than that of Eo treatment,indicating that BC@Eo prolonged the bactericidal activity of Eo against E.vexans.4.The antibacterial mechanism of the main antibacterial ingredient citral on E.vexans was preliminarily clarified.Optical microscopy（OM）,scanning electron microscopy（SEM）and transmission electron microscopy（TEM）were used to observe the effects of citral MIC concentration treatment on E.vexans mycelial structure.On the 7th day after treatment,OM and SEM observation results showed that citral would cause abnormal hyphal morphology,including hyphal dissolution,cohesion,shrinkage,and tumor-like formation on the surface of hyphae;After treatment,the cell wall was damaged,the liposomes in the mycelium were dispersed and increased,and the internal structure was blurred.Cellulase,superoxide dismutase（SOD）,peroxidase（POD）,succinate dehydrogenase（SHD）,malate dehydrogenase（MDH）and malondialdehyde（MDA）kits were used for evaluation The effect of citral on the physiological and biochemical characteristics of Tea blister blight disease pathogen.The results show that citral may decompose the cellulose on the cell wall by increasing the activity of cellulase,so as to achieve the purpose of destroying the structure of the cell wall;by reducing the enzymatic activity of the antioxidant enzymes SOD and POD on the cell membrane,the lipid of the cell membrane is more easily oxidized,The cell membrane is damaged,resulting in the increase of malondialdehyde（MDA）content,thereby inhibiting the growth of Tea blister blight disease bacteria;it can also reduce the enzyme activity of metabolic enzymes SDH and MDH,resulting in damage to cell mitochondria and affecting metabolism.Thus inhibiting the growth of mycelium.Through the research in this paper,an improved spore shot method was established,and it was determined that the best antibacterial active ingredient of citronella oil against Tea blister blight disease bacteria was citral,and the tea stem porous carbon controlled release agent was successfully prepared;The antibacterial active ingredient was citral,and the antibacterial mechanism of citral on E.vexans was preliminarily clarified.The results preliminarily confirmed that it was feasible to use porous biocarbon materials to control the release of volatile plant-derived active ingredients,which provided a reference for the use of plant volatiles to control Tea blister blight disease.