| China’s blueberry planting industry has only developed for more than 20 years,and there is still little research on biological control of blueberry diseases.Blueberry leaf spot is an important fungal disease that seriously affects the quality and yield of blueberry,and Pestalotiopsis clavispora is one of the main pathogenic bacteria causing blueberry leaf spot.For Pestalotiopsis clavispora pathogenesis systematic screening of bacteriostatic plant extracts,extraction process and antibacterial mechanism research of extracts have not been reported in China.In this study,blueberry leaf spot bacteria（Pestalotiopsis clavispora）were used as the target bacteria,extracts with good bacteriostatic effect were screened out by hyphae growth rate method,and hyphae growth and spore germination virulence tests were carried out to determine the extracts with the best bacteriostatic effect.The category of bacteriostatic active substances was qualitatively analyzed to explore the optimal extraction process.On this basis,its effect on the physiological characteristics of Pestalotiopsis clavispora bacteria was studied,and its antibacterial physiological mechanism was explored.The results of the study are as follows:1.Among the crude extracts and different solvent extracts of 10 kinds of plants such as Magnoliae.Magnoliae,Cnidium monnier and Pogostemon cablin,crude extracts and petroleum ether extracts were in the forefront of inhibiting the growth of Pestalotiopsis clavispora fungus.The inhibition of magnolia petroleum ether extract from Magnoliae.Magnoliae,Cnidium monnier and Pogostemon cablin on the growth of Pogostemon cablin mycelium and spore germination were IC50 of Magnoliae petroleum ether extract<IC50 of Cnidium monnier petroleum ether extract<IC50 of Pogostemon cablin petroleum ether extract,and Magnoliae petroleum ether extract had the strongest inhibitory effect on the growth of Pestalotiopsis clavispora mycelium and spore germination of 0.16mg/m L and 0.23 mg/m L.2.Preliminary qualitative detection of the bacteriostatic active substance category of Magnoliae petroleum ether extract was carried out through test tube test,and it was preliminarily determined that the bacteriostatic active substance of Magnoliae petroleum ether extract was mainly phenolic substances.The comparative test of extraction solvent showed that the antibacterial activity of the extract obtained by using ethanol as the extraction solvent and then extracting with petroleum ether was better than that obtained by directly using petroleum ether as the extraction solvent.Using the single-factor test and Box-Benhnken experimental design method,the optimal process conditions for the extraction of Magnoliae petroleum ether extract by ultrasound-assisted method were as follows:ethanol concentration 80.16%,material-liquid ratio 1:20.49（g/m L）,extraction temperature 52.43℃,under these conditions,the theoretical inhibition rate of Magnoliae petroleum ether extract with a mass concentration of 0.2 mg/m L on the growth of mycelium growth of blueberry leaf spot fungus was 58.24%.And the response surface model fits and predicts well.3.The effect of Magnoliae petroleum ether extract on the physiological characteristics of mycelium was determined by conventional methods,and it was found that Magnoliae petroleum ether extract destroyed the semi-permeability of mycelium cell membrane,and the electrolyte exudation rate of mycelium increased with the increase of Magnoliae petroleum ether extract treatment concentration;Magnoliae petroleum ether extract increased the content of malondialdehyde,a lipid peroxidation product of mycelial cell membrane,and destroyed the cell membrane structure.Magnoliae petroleum ether extract inhibited the synthesis or degradation of myceliumpyruvate,which reduced the content of myceliumpyruvate,thereby affecting the energy metabolism process of mycelium.The contents of hyphae soluble protein and soluble sugar treated with Magnoliae petroleum ether extract decreased,which affected the osmoregulation function of mycelium.Magnoliae petroleum ether extract has a certain interference and destructive effect on the mycelial defense enzyme system,and with the increase of the concentration of Magnoliae petroleum ether extract,the activities of mycelium peroxidase and polyphenol oxidase first increase and then decrease.This study found that Magnoliae petroleum ether extract had strong bacteriostatic activity against Pestalotiopsis clavispora,preliminarily determined that its bacteriostatic active substance was phenolic,and obtained its optimized extraction conditions,and the physiological mechanism of antibacterial was discussed,aiming to find the source of plant-derived active substance with good inhibitory effect on Pestalotiopsis clavispora and lay the foundation for the development of plant-derived pesticides for the prevention and control of blueberry leaf spot. |
PDF Full Text Request