The effect of a seed coating with Origanum vulgare essential oil on Clavibacter michiganensis subsp. michiganensis

The study aimed to evaluate the efficacy of a seed film coating with Origanum vulgare Linnaeus essential oil (EO) against Clavibacter michiganensis subsp. michiganensis (Cmm) on tomatoes. Tomato seeds (cv. Rio Grande) coated with different doses of EO derived from O. vulgare were inoculated with Cmm (1.8 x 108 CFU/mL). O. vulgare's EO showed a remarkable inhibition effect on the Cmm growth. The EO effect against Cmm was determined based on the parameters, such as the inhibition zone and bacterial population in a seed. The GC-MS analysis of EO showed that carvacrol is the major component (at 74.05%), which may inhibit the bacterial growth. Later, we have expanded our studies to determine the inhibitory effect of the EO's mode of action on the pathogenic bacteria with a molecular docking analysis based on the molecular protein-ligand interaction. The results showed that carvacrol has a strong interaction with the bacterial expansin protein (PDB 411O) of Cmm and the qPCR analyses confirmed the effect of the O. vulgare treatment against Cmm. This original approach has the prominent potential to prevent seed transmission of Cmm for seed quality in the world, suggesting a method for paving the way for Cmm disease management.