Isolation Of Antagonistic Bacteria Against Fusarium Graminearum,Identification Of Antagonistic Substances And Biocontrol Application

Fusarium head blight(FHB)caused by pathogenic fungi may decrease yield and quality of wheat and barley.Fungal pathogens also produce mycotoxins in wheat crops,especially including deoxynivalenol(DON)which pose a threat to dietary safety and human health.At present,Methods to control FHB of wheat include cultivation of resistant wheat,chemical control,biological control,in which the chemical control is the most effective measure.But the cost of pesticides productions is high and they also have negative impacts on the environment.People are looking for other ways to control FHB,hoping to be free of chemical pesticides,to ensure environmental safety.Biological control not only causes the lower impact to environment.it also helps to reduce the dependence of wheat on chemicals,to slow down the development of drug resistance.So it has received widespread attention.The research content of this paper is the isolation of antagonistic bacteria against Fusarium graminearum,identification of antagonistic substances and bio-control application.First,soil samples were collected from all parts of Jiangsu Province,and then diluted and spread on LB plate.After the colonies were grown,The confrontation experiment was performed withFusarium sp.as the target.The strains with transparent antifungal bands were selected for purification and re-verification.191 antagonistic bacteria were isolated in the study,The inhibition diameter on LB and PDA medium was 13.2 mm and 12.4 mm on average.Among them,HB10 had better antagonistic effect than other strains,and the inhibition diameter on LB and PDA was more than 28 mm.HB10 is a strain belong to Streptomyces netropsis,which has no reports on the antagonistic activity against Fusarium sp..Then,the antagonistic substance of HB10 was isolated and identified,and the crude extract of HB10 was obtained by extracting with n-butanol.The crude extract was then purified by gel column chromatography and scanned at full wavelength under UV spectrophotometer.The UV absorption peaks of the antagonistic crude extract were mainly at 220 nm and 338 nm.The antagonistic substance was prepared by HPLC and detected the antagonism.The purified antagonistic substance was identified by mass spectrometry and nuclear magnetic resonance spectroscopy.In the end,The antagonistic substance was identified as the Aureothin.Finally,pot experiment was made,The wheat collected from experimental base were cultured with spore of Fusarium graminearum in artificial climate incubators.After the survival of wheat,the HB10 was sprayed onto the soil and the surface of wheat.The total DNA was extracted from the root soil every week.The change of Fusarium graminearum concentration in soil was quantitatively determined by real-time quantitative PCR.The results showed that the antagonistic effect of HB10 was prominent,and amount of Fusarium graminearum was decresed in the second week,The results of this test laid the foundation for the field application of antagonistic bacteria HB10.