Abstract: An antagonistic strain was screened from wormcast and it inhibited the Fusarium oxyporum f. sp. cucumerinum（Foc）,and its inhibitory capability was improved via optimizing culture condition. Using the Foc as experimental pathogen and wormcast as the experimental material,an antagonistic strain named WQ-5 with strong antagonistic activity to Foc was isolated using dilution plate coating and plate confrontation method. The strain WQ-5 was identified by morphological observation,physiological and biochemical characteristics and 16S rRNA sequence analysis. The culture conditions were optimized by single factor and response surface analysis,and its control effect was verified by seed germination test and pot experiment. The strain WQ-5 was identified as Bacillus amyloliquefaciens. The optimized culture conditions,i.e. fructose 30 g/L,peptone 18.9 g/L,magnesium sulfate 3 g/L,glycerol 1 g/L,dipotassium hydrogen phosphate 1.5 g/L,pH 5.8,liquid-loading rate 38.6%,rotating speed 240 r/min,inoculation rate 5%,temperature 30℃ and cultural time 24 h,increased inhibition zone diameter by 24.8% and the inhibition rate of pathogens by 30.39%,as compared to the non-optimized conditions. The control effect experiment showed that the strain WQ-5 reduced the disease incidence of seeds by 20%,increased germination rate by 150%,significantly enhanced the root length,stem length and vigor index of seeds,decreased the disease index of plants by 48.65%,and decreased the disease index of plants by 51.67%. In conclusion,the strain WQ-5 demonstrates promising control effect on Fusarium wilt caused by Foc and presents potential research and application value.

Key words: wormcast, antagonistic bacterium, Fusarium oxyporum f. sp. cucumerinum, culture conditions, response surface analysis