Biological control of leaf disease of barley with Bacillus strain.

A new Bacillus amyloliquefaciens subsp. plantarum strain IMV B-7404 was selected by an in-vitro agar plate assay as a potential biological control agent. The strain strongly inhibited the growth of 12 important plant pathogenic fungi. In growth chamber assays, the severity of spot blotch of barley decreased when culture filtrate was applied on leaves or was introduced into the plant growth medium before fungal inoculation. Apparently, the metabolites of strain IMV B-7404 play a role in disease prevention, which indicates that the strain can stimulate induced systemic resistance (ISR). When the cell suspension was sprayed onto leaves, the disease severity depended on environmental and, probably, some other conditions. We suggest that effective biological control by Bacillus-based products depends on spraying leaves with the cell suspension to co-ordinate with the process of plant infection by the pathogen. The ecological behaviour and biology of both the antagonist and the target pathogen are the key elements in enhancing the efficacy of biocontrol products. It is necessary to know the stage of infection that is most vulnerable. This information needs to be identified individually for each pathosystem and in relation to environmental conditions. [ABSTRACT FROM AUTHOR]