| Plant diseases are a major problem encountered in sustainable agriculture and bring great losses to agricultural production.However,chemical pesticides can leave behind various problems.Therefore,the efficient development of novel biologically active compounds for use as agricultural fungicides has become a hot topic.And endophytic fungi have been shown to produce many bioactive compounds.Therefore,Aureobasidium pullulans were studied to screen for sites with anti-plant pathogenic fungal activity.The anti-Cylindrocarpon destructan activity of A.pullulans ethyl acetate extract was measured,and to investigate its secondary metabolites to identify of its major antifungal active ingredients.The main results obtained in this thesis are as follows:1.Firstly,the endophytic fungus A.pullulans was identified by molecular biology.The inhibition activity of the different polar parts of A.pullulans solid fermentation against nine plant pathogenic fungi were determined.The ethyl acetate extract showed significant inhibition activity against the plant pathogenic fungi.The inhibitory rate of the ethyl acetate extract against C.destructan reached 100%at 15 mg/m L.2.The effect of ethyl acetate extract on the cell membrane of C.destructan was investigated.It was found that the mycelial growth of C.destructan was significantly inhibited by ethyl acetate extract,with the minimum inhibitory concentration of 1.88 mg/m L and the minimum fungicidal concentration of 15 mg/m L.The mycelial morphology of C.destructan treated with ethyl acetate extract was significantly changed,with the mycelium wilted and dried,the surface was uneven,and some of the mycelial contents were leaked.Ethyl acetate extract could increase the extracellular conductivity and nucleic acid content,and also increased the contents of the MDA and H2O2,and the activities of POD and CAT were abnormal.In conclusion,ethyl acetate extract could induce ROS generation that causes lipid peroxidation,resulting in cell membrane injury,solute and electrolyte leakage,and subsequent cell death.3.The secondary metabolites of A.pullulans were studied and 18 compounds were isolated as 3,4-dimethoxy-5-methylbenzene-O-α-D-glucopyranoside（1）,5’-hydroxygriseoful vin（2）,7-dechlorogriseofulvin（3）,6’-hydroxygriseofulvin（4）,（2S,5′R,6′R）-7-dechloro-5′-hydroxygriseofulvin（5）,4-（4-hydroxybenzyl）-5-methylbenzene-1,3-diol（6）,p-hydroxypheny lethanol（7）,p-hydroxybenzoic acid（8）,orcinol（9）,2,4-dihydroxy-6-methylbenzaldehyde（10）,1-（furan-2-yl）ethane-1,2-diol（11）,1-（furan-2-yl）-2-hydroxyethan-1-one（12）,4,6-dimet hoxyisobenzofuran-1（3H）-one（13）,4-hydroxy-6-methoxyisobenzofuran-1（3H）-one（14）,olei c acid（15）,linoleic acid（16）,methyl linoleate（17）,ethyl linoleate（18）.All of the abo ve compounds were isolated from A.pullulans for the first time,with compound 1 was a new compound. |
