Biocontrol impact of AHL degrading actinobacteria on quorum sensing regulated virulence of phytopathogenPectobacterium carotovorumsubsp.carotovorumBR1

Aims The aim of this study was to isolate soilborne AHL degrading actinobacteria that can be used as biocontrol agents against the quorum sensing mediated virulence ofPectobacterium carotovorumsubsp.carotovorumBR1 in in vitro andin plantastudies. Methods Actinobacterial strains capable of N-acyl homoserine lactone (AHL) degradation,Glutamicibacter nicotianaeAI5a andRhodococcus pyridinivoransAI4 were isolated and screened usingChromobacterium violaceumCV026 as a biosensor in an AHL degradation bioassay. The effect of AHL degradation by the potential biocontrol strains was studied by a co-culture assay. Reduction in plant cell wall degrading enzymes produced byPccBR1 due to the quorum quenching activity of the potential biocontrol strains was studied using colorimetric assays. The ability of the isolates to reduce soft rot symptoms was studied in in vitro cucumber and potato maceration assays. A cucumber plant infection model was developed to study blackleg in greenhouse experiments. Results G. nicotianaeAI5a, R. pyridinivoransAI4 andR. erythropolisCRD13.3C were able to reduce 3-oxo-C6- N-acyl homoserine lactone and production of plant cell wall degrading enzymes byPccBR1. The isolates were also able to prevent and attenuate soft rot caused byPccBR1 in vitro in potato and cucumber maceration assays. The isolates were also able to prevent blackleg in anin plantacucumber infection model. Conclusions Among the three actinobacterial isolates,G. nicotianaeAI5a showed best results and has immense potential as a biocontrol agent against the virulence of the quorum sensing phytopathogenPccBR1.