Study On The Antagonistic Mechanism And Evaluation Of Biocontrol Potential Of Chaetomium Globosum 61239 Against Cytospora Mali

Apple Valsa Canker,caused by Cytospora mali,is a devastating apple trunk disease that seriously threatens apple production.At present,the prevention and control of this disease mainly rely on scar scraping and chemical agent smearing,which is time-consuming,laborious,polluting the environment,and has poor prevention effect.Therefore,it is urgent to explore an efficient and green disease prevention and control method A strain 61239 was previously isolated which had strong antagonistic activity against C.mali,and has good biocontrol potential.In this study,the antimicrobial spectrum of strain 61239 and the inhibitory activity of its metabolites on C.mali were confirmed by culture confrontation experiments;the colonization ability of the strain on apple branches,and the protective and therapeutic effect of the strain toward apple valsa canker were clarified by artificial inoculation.The antagonistic mechanism of the strain was dissected by means of metabolite analysis and gene silencing.Main findings obtained are as follows:1.The 61239 strain has highly effective antagonistic activity against plant pathogens such as C.mali and Rhizoctonia cerealis,among which the antagonistic activity against C.mali is the strongest.This antagonistic activity is dependent on secreted secondary metabolites.2.The PDB fermentation broth of the 61239 strain is rich in the metabolite chaetoglobosin A(Ch A),and pure chaetoglobosin A has a significant inhibitory effect on the mycelial growth of C.mali,and silencing of PKS-NRPS(che A)and ER(che B),two key genes within the synthesis pathway of chaetoglobosin A,significantly reduced the antagonistic activity of the fermentation broth of strain 61239,which indicated that chaetoglobosin A was the key antagonistic metabolite.3.The colonization ability of the 61239 strain on healthy apple branches was weak,but exogenous nutrition could promote the colonization of the strain.The fermentation broth had obvious protective and therapeutic effects on apple valsa canker.In conclusion,this study confirmed that the high antagonistic activity of strain 61239 against apple valsa canker depends on the secondary metabolite chaetoglobosin A,and the metabolite has obvious protective and therapeutic effects on apple valsa canker.The results of this study lay an important foundation for subsequent development of green prevention and control technologies for apple rot disease.