Effects of sub-bactericidal concentration of plant essential oils on pathogenicity factors of Ralstonia solanacearum

Ralstonia solanacearum is a complex bacterial species that causes the very destructive plant disease, bacterial wilt, on many solanaceous species and also several other plant families in tropical, subtropical and some temperate regions of the world. In this study, the inhibitory effects of three sub-bactericidal concentrations of the Cinnamon (Cinnamomum zeylanicum), Thyme (Thymus vulgaris), lavender (Lavandula angustifolia) and eucalyptus (Eucalyptus camaldulensis) essential oils (EOs) were evaluated on biofilm formation, the swimming, swarming and twitching motilities of R. solanacearum race three strains. Furthermore, the effects of EOs on bacterial morphology were assessed. All treatments caused significant reductions in biofilm formation and on the ability to swim, swarm and twitch of bacterial cells. The results also indicated that sub-lethal concentrations of EOs which were applied in this study caused abnormality in the shape of bacterial cells and changed the R. solanacearum morphology. The results obtained indicated that the sub-bactericidal concentrations of EOs applied in this study suppressed R. solanacearum pathogenicity and virulence factors. Because of less phytotoxicity at these concentrations and lower costs of their application, they can be used as environment-friendly biofumigants.