Isolation And Identification Of Bioactive Metabolites From Endophytic Fungi Against Wheat Powdery Mildew

Wheat powdery mildew,caused by Blumeriagraminis f.sp.tritici(Bgt)is one of the devastating diseases to wheat production in China.Its frequent epidemic occurrences have caused substantial yield losses across diverse geographicalgrowing regionsin China.The current major controlling methods against wheat powdery mildew are utilization of fungicides and resistantwheat cultivars,both arenot working effective enough.The powdery mildewhas the capacity to evolve fast by mutations to create new races,which can easily overcome the resistant of cultivars in use.Thechemicalfungicides were mainly not environmental-friendly,and longtime reliance on it has induced pesticides-resistance of the pathogen.So,researchesof newthe bio-antagonists are necessaryto provide safe and efficient controlling method against wheat powdery disease.The dissertation describes the isolation of a fungal endophyte LPS-1 from the stem of health Ilex comuta,as well as the biological efficacytest of fermentation products on wheat powdery mildew,identification of endophyteLPS-1,and optimization of fermentation conditions.The results of the study are as follows:(1)207 entophyte were successfully obtainedfrom the tissue materialof healthy plantsfrom 28 species in 24 families.The result of efficacy test on leaf in vitroshowedinhibition ratioLPS-1,16-6 and SCS-6 were more than 90%,andLPS-1 was selected as the intense research target strain after the secondary screening.Protective and therapeutic effectiveness testin vivo tests showed LPS-I works effectively against wheat powdery mildew.(2)The sporesof LPS-1 fungus shapedin oval or round with obtusetip,colorless,the spore size is 25.0?25.4×14.3?4.5?m.The phylogenetic tree based on ITS sequence showed its most similarity to Lasiodiplodiapseudotheobromae with 100%identity.The characteristics of morphology and the analysis of DNA sequences suggest that the fungus LPS-1 was identified as Lasiodiplodiapseudotheobromae.(3)The single factor experiments of fermentation conditions of strains LPS-1 were studied and optimized culture medium componentswere determined.The suitable liquid medium were 19.95 gL-1 malt extract,50 gL-1 sucrose,7.5 gL-1NaNO3 and 3.51 gL-1 MgSO4·7H2O.The suitable incubation conditions:30mLmedium in 100 mLflask,inoculate three mycelium agar block in each flask,shake fermentationat 28? for 48hours,and then static fermentation for 6 days.(4)The dry power of LPS-1 fermentation filtrate was obtained by diethyl ether and ethyl acetate extraction.The ethyl acetate extract contains most active compound with inhibition ratio up to 87.2±2.5%at concentration of 10mg/L.Two compounds were obtained by combination of silica gel column chromatography,spectral analysis and high performance preparative liquid chromatography.Farther study with NMRidentified them to be Indole-3-carbxlic Acid?Indole-3-carbaldehyde.