Screening and antagonistic characteristics of antagonistic bacteria against Fusarium graminearum

【Objective】To isolate strains with inhibitory function against Fusarium graminearum from soil of wheat plant,and to provide bacterial strain resources for prevention and control of wheat scab and toxin contamination.【Method】Wheat rhizosphere soil was used as material to screen strains that could inhibit F. graminearum growth by plate confrontation method. Antagonistic bacteria were identified according to colony morphology,physiological and biochemical properties and 16S rDNA phylogenetic analysis.The antagonistic characteristics of antagonistic bacteria were investigated by PCR amplification of antibacterial lipopeptide gene,fermentation condition test and antibacterial property analysis of antibacterial substances. The control effect of antagonistic bacteria on wheat scab and the inhibitory effect on deoxynivalenol(DON) were verified by inoculation of wheat ears and wheat grains.【Result】Five strains of bacteria with antagonistic effect against F. graminearum were isolated from wheat rhizosphere soil,among which the strain XW-10 with the best antagonistic effect was identified as Bacillus amyloliquefaciens which had genes involved in biosynthetic pathways of lipopeptides such as iturin,surfactin and fengysin. The optimum condition for the growth of strain XW-10 was cultured in CM medium for 10-48 h. Antagonistic substances,mainly found in the fermentation supernatant could significantly inhibit mycelial growth,decrease spore germinationrate and distort hyphae morphology. The cell-free supernatant maintained stable antimicrobial activity at temperatures below 90 ℃,and the antimicrobial activity peaked at neutral pH. Antagonistic characteristics of antagonistic bacteria were determined by PCR amplification of the antibacterial lipopeptide gene,fermentation condition test and antibacterial properties analysis of bacteriostatic substance. According to wheat ear and wheat kernel inoculation test,the efficient component of cell-free supernatant was crude protein,but it was not sensitive to effects of papain,trypsin and protease K. The experiment showed that cell-free supernatant of strain XW-10 could promote wheat seedling growth,reduce DON toxin content in wheat matrix and wheat scab incidence by inhibiting F. graminearum growth.【Conclusion】The screened strain XW-10 can significantly prevent and control wheat scab and significantly inhibit DON toxin,showing its potential to be a wheat scab biocontrol bacterium.