Isolation, Identification And Antifungal Activity Of The Biocontrol Strain Chaetomium Spp.

Plant diseases caused by plant pathogens, is the enemy of agricultural industry.Currently, the most effective and common measure to prevent plant disease is to usechemical fungicides. However, with the extensive application of chemical pesticides, itsdrawbacks gradually revealed. Thus, people start looking for safer, more effectivealternatives to chemical pesticides. Microbial control of plant diseases has a long history,and the mechanisms are varied. Chaetomium spp. is a widely used biocontrol agents,and has been reported to be an antagonist of various plant pathogens.1. The strain Mi2A was isolated from soil and was identified as Chaetomiumglobosum based on its morphological features and the molecular phylogenic analyses.2. The fermentation broth of C. globosum Mi2A showed antifungal activity againstsix common plant pathogenic fungi. The fermentation broth, mycelia, and solid-statefermented rice culture were extracted with ethyl acetate respectively to give three kindsof crude extracts. These three kinds of crude extracts showed potent antifungal activityagainst Fusarium graminearum, Corynespora cassiicola, and Alternaria mali.Furthermore, different crude extract showed different antifungal activity. Thus, it can beinferred that the antifungal ingredients the crude extract contained are different. Thecrude extract of mycelia exhibited higher antifungal activity against plant pathogenicfungi than the others. Treatment with it at1mg/mL suppressed the development of thethree plant pathogenic fungi by over50%, and even suppressed the development ofFusarium graminearum by71.11.3. By the means of silica gel column chromatography and Sephadex LH-20columnchromatography, seven compounds were isolated. These compounds were identified byspectroscopic techniques combined with literature data. Chaetoviridin B andchaetoviridin D were isolated from the fermentation broth, chaetoviridin E andchaetoviridin A were isolated from the mycelia, ergosta-5,7,22-trien-3beta-ol，chaetoglobosin Gå'Œchaetoglobosin B were isolated from the solid-state fermented riceculture. Chaetoviridin E, chaetoviridin A and chaetoglobosin B exhibited higher antifungal activity against plant pathogenic fungi than the others. Chaetoviridin Aexhibited the highest antifungal activity against plant pathogenic fungi, and the EC50value of chaetoviridin A against Fusarium graminearum, Corynespora cassiicola, andAlternaria mali were57.1μg/mL,102.4μg/mL and61.08μg/mL, respectively.