Screening of Antagonistic Bacteria CL-1 Against Banana Wilt Disease and Optimization of the Fermentation Conditions

The microbial strains were isolated from the rhizosphere soil of banana orchard without disease, and Fusarium oxysporum f.sp.cubense Tropical Race 4 (Foc TR4) was used as the target strain to screen the high-efficiency antagonistic strains of Foc TR4, which provided a new choice for the green prevention and control of banana fusarium wilt. The rhizosphere soil from banana plantation in the horticultural greenhouse of Huaqiao University was collected, and the excellent antagonistic strains were screened by using the dilution coating and plate confrontation methods, and the culture conditions were optimized. The results showed that three antagonistic strains were isolated from the soil of banana garden, among which CL-1 strain had the best antagonistic effect, with an inhibition rate of 34.25%. The 16 S rRNA sequencing results showed that the strain had a similarity of 99.38% with Stenotrophomonas maltophilia, and was preliminarily identified as Stenotrophomonas maltophilia. The single factor culture conditions for CL-1 strain were optimized. The optimal culture medium for CL-1 strain was beef extract of 5 g·L⁻¹, peptone of 10 g·L⁻¹, and calcium chloride of 5 g·L⁻¹. After the optimization, the antibacterial rate was increased to 45.21%. The CL-1 strain could effectively inhibit the growth of banana Foc TR4 and had good biocontrol potential.