Biological control of bacterial soft rot in Chinese cabbage by Lactobacillus plantarum strain BY under field conditions

•Lactic acid bacteria (LAB) were screened for the ability to control plant diseases.•Lactobacillus plantarum strain BY suppressed bacterial soft rot on various crops.•BY populations persisted especially on wounded plant leaves.•BY showed antibacterial activity against soft rot pathogen.•First report on application of LAB for biological control under field conditions. Bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum is one of the most important diseases of Chinese cabbage. To develop a microbial pesticide that is not only safe but also easily acceptable by consumers, we screened strains of lactic acid bacteria for biocontrol potential. One of 1166 isolates, Lactobacillus plantarum strain BY significantly reduced soft rot disease severity in Chinese cabbage in six different fields in Japan. This isolate also suppressed disease in onion, potato, and tomato. BY populations persisted on wounded Chinese cabbage leaves after spraying. Moreover, BY inhibits pathogen growth in an antibiosis assay. These results strongly suggest that BY inhibits the invasion of the pathogen at wounded sites on leaves and its proliferation in host tissues. This is the first report indicating the application of lactic acid bacteria for biological control of a plant disease under field conditions.