Biological Control of Crown and Root Rot and Bacterial Wilt of Tomato by Bacillus subtilis NB22.

Abstract

B. subtilis str. NB22 strongly suppressed the growth of 19 plant pathogenic fungi and 8 bacteria tested in vitro. In field trials, when rice straw was immersed in a culture suspension of NB22 and then mixed with soils infested with Fusarium oxysporum f.sp. radicis-lycopersici the subsequent occurrence of crown and root rot of tomato was reduced. When combined with steam sterilization, the suppressive effect of NB22 was conspicuously enhanced and yields were 3-4 times greater than in the unsterilized controls. Bacterial wilt caused by Pseudomonas solanacearum was also suppressed when a culture suspension of NB22 was poured into heavily infested soils, and the percentage of dead plants was much reduced. The results suggest that NB22 has a wide range of antifungal and antibacterial activities and can be used as a biological control agent for these soilborne diseases of tomato.