Biological evaluation of 32 different essential oils against Acidovorax citrulli, with a focus on Cinnamomum verum essential oil
Bacterial fruit blotch (BFB) of watermelon caused by Acidovorax citrulli (ACC) is one of the most severe diseases of watermelon worldwide. Antibacterial activity of 32 essential oils (EOs) was evaluated against ACC using disk-diffusion assays. The oil from cinnamon exhibited the greatest antibacterial activity. Using gas chromatography-mass spectrometry (GC-MS), the major components of cinnamon oil were analyzed. Among the various components of cinnamon oil, benzaldehyde and cinnamaldehyde exhibited the effective antibacterial activities against ACC. The minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of benzaldehyde and cinnamaldehyde were measured using broth dilution assays. The MICs against ACC of benzaldehyde and cinnamaldehyde were 0.1 and 0.01% (v/v), respectively. The MBCs of benzaldehyde and cinnamaldehyde against ACC were 0.2 and 0.02% (v/v), respectively. Also, 0.2% (v/v) levels of cinnamon oil, benzaldehyde and cinnamaldehyde completely killed ACC cells artificially contaminating watermelon seeds. This study suggests that cinnamon oil and its bioactive components, benzaldehyde and cinnamaldehyde, have potential for application as natural agents for the prevention and treatment of BFB.
Key words: Acidovorax citrulli, bacterial fruit blotch, cinnamon oil, essential oil.