Abstract: A strain of Bacillus velezensis ZJ1 with good inhibitory efficiency against tomato early blight and gray mold caused by Alternaria solani and Botrytis cinerea was accquired by using the dual culture. The freeze drying method and biocompatibility test were used to select the optimal formula of bacterial agent, the field efficacy and the growth-promoting effect of ZJ1 oil suspension was determined. The optimum formulation of ZJ1 strain oil suspension was 10% bacteria powder (6.0×10¹⁰cfu/g), 7% (v/v) Tween80, 50 μg/mL amphotericin, 2% CaCl₂, 1% SDS, 1% CaCO₃, 0.5% calcium lentisulfonate, 5% dextrin, peanut oil to complement to 100%, the spores content is 5.75×10⁹cfu/mL. All indexes were in line with national standards. The B.velezensis ZJ1 oil suspension with the dilution of 200× had the best biocontrol effect on tomato early blight and gray mold caused by A.solani and B.cinerea, the protective and therapeutic effects can reach more than 90%, and has obvious growth-promoting effect, and could significantly increase the stem diameter. The preparation of this biocontrol agent is environmentally friendly and highly-efficient, and has stable effect, which lays a foundation for its production and application in fields.

Key words: Bacillus velezensis, oil suspension, tomato early blight and gray mold, field control efficacy, growth- promoting