Isolation, Indentification Of Antagnistic Bacteria Against Fusarium Graminearium And Study On Their Antagonistic Characteristics

Fusarium Head Blight (FHB) is the most devastating disease on cereal crops caused by Fusarium graminearum. This disease not only causes significant economical losses but also poses threats to human and animal health by contanminating grains with mycotoxins. Currently, due to the lack of resistant wheat cultivars and effective and low toxic fungicides against F. graminearum, biocontrol has become a research hotspot in the integrated management of FHB. In this study we isolated bacteria which showed antagonistic effects against F. graminearum from soil, characterized their antagonistic activity, and then studied the active antagonistic substance produced by the bacteria. The main contents are as follows:Screen of antagonistic bacteria against F. graminearum:We obtained colonies from the field and then sprayed F. graminearum spores to them.The antagonistic bacteria were selected by observing the inhibition zone which colonies produced. Bacteria with larger inhibition zone were picked to and tested their antagonistic activities against seven pathogens. Finally, two stains named 7A1 and 7F1 with high antagonistic effect had be chosen.The two strains 7A1 and 7F1 were then identified as Bacillus spp. and Paenibacillus polymyxa according to the morphological, physiological, biochemical characteristics and 16S rDNA gene sequence.Characterization of antagonistic bacteria against F. graminearum:Both strains could inhibit the spore germination and hyphal growth of F.graminearum. The inhibitory rate of strain 7A1 and 7F1 to several pathogenic fungi is higher than 60%. In laboratory,7A1 and 7F1 could reduce the incidence of wheat scab by 44.4% and 57.9% respectively.7A1 could also biodegradable Zearalenone toxin produced by F. graminearum.Investigation of the active antagonistic substance produced by the bacteria:In order to clarify the mechanism of inhibition activity of 7A1 and 7F1, the distribution of antagonistic substances was studied and found to be mainly distributed in cell supernatant. The effects of temperature, pH, proteinase K, and chloroform on the inhibition activity of antagonistic substance in 7A1 and 7F1 were then studied. The results showed that antagonistic substance of 7A1 and 7F1 were stable in temperature lower than 60℃ and 70℃ respectively, but when temperature was higher than 70 ℃the inhibition activity decreased rapidiy, and lost the activity when reach 100 ℃. The antagonistic substance of 7A1 and 7F1 were stable in neutral conditions. The inhibition activity of antagonistic substances in 7A1 and 7F1 were declined when treated with proteinase K, pepsin, trypsin, chloroform and UV.