Study On The Antibacterial Effect Of Polygonum Orientale Essential Oils Against Three Plant Pathogens

Clavibacter michiganensis subsp.sepedonicus,Clavibacter michiganensis subsp.michiganensis and Pectobacterium carotovorum subsp.carotovorum,are seriously harmful to agricultural production.Chemical bactericides which bring huge dangers to the ecological environment are commonly used as control measures.Botanical bactericides have received widespread attention because of their many advantages,and the sources of botanical bactericides include essential oils.Polygonum orientale is a kind of aquatic plants.In this study,the antibacterial effects of P.orientale essential oils on three pathogens were studied.The research contents and results are as follows:1.Optimization of extraction process and component analysis of P.orientale essential oilsThe P.orientale essential oils were extracted by steam distillation.Based on single factor experiment results,the optimum extraction condition of the P.orientale essential oils was obtained by response surface methodology.The condition was as follow: soaking time was 2.6h,extraction time was 7.7h,and the ratio of liquid to material was 10.3 times.The results of bacteriostatic activity showed that the P.orientale essential oils had significant antibacterial effects on three pathogens,and the MIC against C.michiganensis subsp.sepedonicus,C.michiganensis subsp.michiganensis and P.carotovorum subsp.carotovorum were 0.625mg/m L,0.313mg/m L,and 0.625mg/m L.The GC-MS was used to analyze the components of essential oils.A total of 29 components were separated,and 23 components of them were identified,mainly including phytol,phytone,pentacosane,mushroom alcohol,and ?-ionone.These compounds could be divided into terpenes,alkanes,ketones and so on.2.Analysis of the antibacterial mechanism of P.orientale essential oilsThe effects of P.orientale essential oils on the morphology and properties of the pathogens were studied by transmission electron microscopy observation,surface potential and hydrophobicity assays.After the action of the P.orientale essential oils,three pathogens were twisted and deformed.The cell separations and vacuoles were obvious,and the cell walls and cell membranes were damaged.A large number of cell fragments appeared after the cell lysis and death.In addition,the surface potential decreased and hydrophobicity increased,which made the stability of pathogens decreased and the adhesiveness increased.These phenomenons led to pathogens to be easily aggregated and denatured.The effects of P.orientale essential oils on the cell walls of the pathogens were analyzed by the change of alkaline phosphatase activity.It can be seen that P.orientale essential oils damaged the cell walls of the pathogens and caused the leakages of alkaline phosphatase.The effects of P.orientale essential oils on the cell membranes of the pathogens were analyzed by the experiments of cell membrane integrity,cell membrane permeability,and key enzyme activity in respiratory metabolism.The results showed that the P.orientale essential oils could destroy the integrity of cell membranes and increase the permeability of cell membranes,and the pathogens were depolarized.The results also showed that the conformations of membrane protein were abnormal,and a large number of K+ and Mg²⁺ were leaked.In addition,P.orientale essential oils inhibited the activities of pyruvate kinase,succinate dehydrogenase and T-ATPase,which weakened the respiration of the pathogens.3.Preparation of botanical bactericide of P.orientale essential oils and analysis of its antibacterial effectsThe formula of botanical bactericide of P.orientale essential oil was determined by solvent screening,emulsifier screening,and toxicity tests.The formula was as follows?according to the mass ratio?: 2% P.orientale essential oils,8% ethanol,8% Tween-20,and water?adding up to 100%?.The results of in vivo experiments and seedling growth experiments showed that the botanical bactericide of P.orientale essential oils had significant control effects against the three pathogens in vivo assays,and also had significant inhibition effects against the three pathogens in seedling stage.In conclusion,P.orientale essential oils had the significant antibacterial effects on three pathogens.This study provided a new green way for controlling the plant diseases caused by the three pathogens,and also provided a scientific basis for the development and utilization of P.orientale.