Isolation, Screening Of Chaetomium Spp.and Preliminary Study On Biocontrol Mechanisms

Chaetomium Kunze is a larger genus of ascomycota, which is world-wide in distribution.Chaetomium spp. is an important resource fungus. As a biocontrol fungus, Chaetomium spp.has a satisfying effect of biocontrol on many plant pathogens.The author obtained80isolates of Chaetomium in the soil from different ecologicalconditions, healthy plants, plant residues, and animal excrement from Tai’an, Feicheng,Xintai, Yishui, Zibo, Zhanhua in Shandong Province, Wuhan and Yichang in Huibei Province,Luoyang in He’nan Province. The80strains were classified into7kinds of fungi Chaetomiumspecies combine morphological comparisons and molecular phylogeny, which wereChaetomium aureum, Chaetomium bostrychodes, Chaetomium funicola, Chaetomiumglobosum, Chaetomium globosporum, Chaetomium megalocarpum and Chaetomium spirale.6strains of Chaetomium spp. were obtained which could impact fully control plantpathogens through according to the daily growth rate of Chaetomium spp., ascomata yield andresults of Chaetomium spp. and plant pathogens in dual culture. They are C. spirale isolateFY2a, C. globosum isolate CH1, C. globosum isolate TY7, C. globosporum isolate61264, C.megalocarpum isolate FYX, C. aureum isolate BR3.Through a series of experimentalbiocontrol mechanisms, a preliminary research was made on the effect of the6strains ofChaetomium spp..The results of dual culture suggested that6strains of Chaetomium spp. showed goodantagonism and competition against Phytophthora capsici, Rhizoctonia solani, Valsa sordida,Curvularia lunata, and Cryphonectria parasitica. There were obvious mycoparasitism ofhyphae of C. spirale isolate FY2a, C. megalocarpum isolate FYX and C. globosporum isolate61264on hyphae of Rhizoctonia solani, as well as C. globosum isolate TY7on hyphae ofPhytophthora capsici.The active substances of Chaetomium spp. suggested that crude extracts of Chaetomiumhad certain inhibitions against the hyphae of Phytophthora capsici C. globosum isolate TY7could significantly inhibit pathogen, and the relative inhibition rate was39.6%. Under the microscopic observation，the hyphae of Phytophthora capsici was obvious bifurcationincreased compared with the control treatment, even local swelling and deformity after treatedwith crude extracts of strain BR3. The hyphae of Phytophthora capsici was lysis in the end ofthe disposition. The fermentation filtrates of Chaetomium had significantly inhibited thegermination of zoospores of Phytophthora capsici. C. spirale isolate FY2a has the bestinhibition effects, and the relative inhibition rate is77.8%. The fermentation filtrates ofChaetomium could affect the germination of pepper seeds. With the fermentation filtrates of C.spirale isolate FY2a and C. globosum CH1, the germination of pepper seeds were promoted,and FY2a is6.5%higher than the control treatment. Conversely, with the fermentationfiltrates of C. megalocarpum FYX, C. globosporum61264and Chaetomium aureum isolateBR3, the germination of pepper seeds were inhibited. The most obvious inhibitory effect isBR3, and the germination rate is18.5%lower than the control treatment.The tests on the activity of Chaetomium’s metabolites suggested that volatile metabolitesof Chaetomium couldn’t inhibit the growth of Phytophthora capsici, while non-volatilesubstances could inhibit it. With increasing concentration of the fermentation filtrates ofChaetomium, the mycelial dry weight of Phytophthora capsici was gradually decreased.Besides, the difference significance analysis showed that there were no significant differencesto mycelial dry weight in the same concentration between moist-dry sterilization and filtersterilization for FY2a, CH1, TY7,61264and FYX. It indicated that the non-volatilesubstances of these5strains had high heat stability. While BR3was significantly different.And it indicated that the non-volatile substances of BR3had low heat stability.Greenhouse trials with fermentation of Chaetomium showed a better resistance to P.capsici by delayling the occuring of Phytophthora blight and decreasing the incidence anddiseases index. C. globosum isolate CH1has the best control efficacy against Phytophthorablight, and the control efficacy was up to83.1%.