Screening and fermentation conditions of antagonistic bacterium against tobacco bacterial wilt

In order to screen antagonistic bacteria against tobacco bacterial wilt, soil samples were collected from the rhizosphere soil of seriously diseased tobacco plants, and six strains (XC1, XC2, XC3, XC4, XC5, DZ1) with strong antagonistic activity were identified by the point contact method. The diameters of antibacterial inhibition zone of the six strains were all above 8 mm. Among them the strain XC4 had a stronger antibacterial activity and stable antagonistic effect. The fermentation conditions were preliminarily studied by a single factor test. The results showed that the optimum fermentation conditions for XC4 were fermenting at 30℃, pH 7.0, inoculum concentration at 2%, 190 r/min for 48 hours with beef extract as carbon source and tryptone as nitrogen source. Under these conditions, the diameter of inhibition zone of XC4 against Ralstonia solanacearum increased by 72%, from 12.5 to 21.5 mm.