Abstract: Bacillus atrophaeus HMB22922 exhibited strong inhibitory activity against the growth of Phytophthora boehmeriae, which caused cotton boll blight. With the purpose of reducing the production cost of B. atrophaeus HMB22922 as well as improving the applicability of preparation made of HMB22922, the fermentation technology for strain HMB22922 was optimized and suitable inert ingredients for wettable powder (WP) were screened. Medium NO. 2 was selected from eleven industrial fermentation media and used as the initial medium, then the media components were further optimized by orthogonal test in shake-flask fermentation. Results showed that soybean flour, yeast extract, corn meal and CaCO₃ were the principal factors affecting the yield of HMB22922, and the optimum dosage of these 4 factors was 13, 3, 30 and 3 g/L, respectively. The optimal initial pH value was 7.0 and the culture temperature was 30℃. Under the optimized culture condition, the number of viable bacteria could reach 2.81×10⁹ cfu/mL. Using the wetting time and suspension rate as indexes, the auxiliaries for HMB22922 were screened. Results showed that the 885 synergistic type B and SP-2836 could be used as the suitable wetting agent and dispersant for HMB22922 WP, and the formula of 2.00×10⁹ cfu/g HMB22922 WP was developed. Control efficacy of the preparation against cotton boll blight was evaluated in the growth chamber. Result showed that the 20-fold dilution of the prepared WP could significantly reduce the disease index, and the control efficacy was 52.16% at 7 days after inoculation with pathogen.

Key words: Bacillus atrophaeus, media, fermentation, preparation