RESUMEN
AIMS: This study aimed to improve the screening strategy for the selection of biocontrol agents with high biocontrol efficacy against fire blight disease. METHODS AND RESULTS: A two-step screening procedure consisting of in-vitro laboratory tests and an ex-vivo test system using detached pear leaves was applied to 43 Bacillus strains originated from the rhizosphere and the aerial parts of apple and pear plants. The grouping of the studied strains and the tested traits based on the principal component analysis and the two-way hierarchical cluster analysis showed that siderophore production and biofilm formation are the most desirable traits in a Bacillus biocontrol agent to control fire blight disease and that rhizospheric originating strains are the most effective. CONCLUSIONS: In contrast to the previous screening strategies that are often insufficient to select the most suitable microorganisms, this study reported an improved strategy based on the microbial competition traits to select potential Bacillus biocontrol agents with high biocontrol efficacy against fire blight disease.