Abstract: To obtain an efficient biocontrol antimicrobial agent against Chinese cabbage soft rot, single factor test and orthogonal test design were used to optimize the fermentation process of Pseudomonas donghuensis ZF510. Subsequently, the appropriate carriers and adjuvants were screened to prepare a wettable powder, and its stability as well as pot control efficacy were evaluated. The results showed that the optimal fermentation medium for strain ZF510 was dextrin 25 g/L, yeast powder 5 g/L, NaCl 1.5 g/L, MgSO₄·7H₂O 1.5 g/L. The optimal fermentation conditions were as follows: fermentation temperature 30 ℃ , pH 8.0, inoculation concentration 2%, 100 mL medium in 250 mL flask, rotation speed 200 rpm. The optimal formulation of WP was white carbon black as carrier, 1.5% Morwet EFW wetting agent, 3% Morwet IP dispersing agent, 0.5% carboxymethyl cellulose as protective agent, 1.5% sodium carboxymethyl cellulose as stabilizer. The viable count of the preparation was 7.9×10¹⁰ CFU/g, wetting time 103 s, suspension rate 80.58%, pH 7.82, the moisture content was 2.11%, impurity rate 2.94%, and the ratio transiting standard test sieve with 74 μm was 97.02%, which was in line with national standards and quality standards. Pot experiment demonstrated the 500-fold wettable powder of Pseudomonas donghuensis ZF510 has a good control effect on Chinese cabbage soft rot, with a control efficacy of 67.92%. This study lays the technical foundation for the development and application of Pseudomonas donghuensis ZF510 wettable powder.

Key words: Pseudomonas donghuensis ZF510, Chinese cabbage soft rot, optimization of fermentation condition, wettable powder, control effect