Isolation,Purification And Structure Identification Of The Antifungal Substances From The Endophytic Fungus CanS-34A

Endophytes are the organisms that live in the plant tissues in part or all of their life history without causing visible harm to plants.In recent years,endophytic fungi have been found to be an important source of biocontrol strains owing to their roles in enhancing plant resistance and production of active metabolites.This research was conducted to clarify the taxonomic status of isolate CanS-34 A of Aspergillus sp.,to evaluatethe suppressive effects of the metabolites of CanS-34 A on mycelial growth,sclerotial germination and plant infection by Sclerotinia sclerotiorum,and to isolate,purify and identify the active antifungal metabolites produced by CanS-34 A.The main results achieved are presented as follows:1.The taxonomic status of isolate CanS-34 A was clarified.Based on morphological features,and DNA sequences of ITS,RPB2,CaM and benA sequences,isolate CanS-34 A was identified as Aspergillus capensis.2.The antifungal metabolites produced by CanS-34 A was found to have suppressive effects on S.sclerotiorum.Isolate CanS-34 A produced antifungal substances(AFS),which effectively inhibited mycelial growth,sclerotial germination and plant infection by S.sclerotiorum.3.Some basic properties of the AFS of CanS-34 A were elucidated.The AFS of CanS-34 A showed thermal stable at 60℃,resistant against UV irradiation,and active in alkaline conditions.The AFS could inhibit the plant pathogenic fungi in the family Sclerotiniaceae and gram-positive bacteria.4.Three antifungal substances were isolated and identified.Using silica gel column chromatography,Sephadex LH-20 gel column chromatography and high performance liquid chromatography(HPLC)to isolate and purify the AFS components.By the nuclear magnetic resonance(NMR),high resolution mass spectrometry and other methods,we identified the structures of active substances.Three AFS compounds,namely penicillither,methyl dichloroasterrate and rosellichalasin,were isolated.These results laid a solid foundation for exploitation of CanS-34 A to control S.sclerotiorum.