Effect of essential oil from Zataria multiflora on local strains of Xanthomonas campestris: An efficient antimicrobial agent for decontamination of seeds of Brassica oleracea var. capitata

In this study, the effect of the essential oil of Zataria multifiora was examined against the local strains of Xanthomonas campestris isolated from the soil. The pathogenicity of the bacteria was confirmed using seedlings on culture media under sterile conditions. The minimum inhibitory and bactericidal concentrations of Zataria multifiora essential oil and two main components (thymol and carvacrol) were evaluated by the microdilution method in microtiter plates. The morphology of the surface of the seeds and characteristics of the grooves were studied by scanning electron microscopy. Hermetic effect of the essential oil and antimicrobial activity of the solvent on X. campestris were evaluated. Minimum inhibitory and bactericidal concentrations of Zataria multifiora essential oil were 231.8 and 463.5 mu g/mL, respectively. The viability of X. campestris in Yeast Malt Broth was reduced by 100% in the presence of Zataria multifiora essential oil (231.8 mu g/mL), while, the seeds contaminated with the same count of X. campestris were disinfected at higher concentration of Zataria multifiora essential oil (463.5 mu g/mL). Killing of X. campestris cells adhered to the seeds with uneven surface and deep grooves required greater concentrations of the essential oil. The impregnation of the seeds in the essential oil at 463.5 mu g/mL showed that a 2-h exposure period causes the least possible damage to the seedlings and is sufficient to prevent the occurrence of the disease caused by X. campestris in Brassica oleracea.