This study was designed to examine the chemical composition and the in vitro antibacterial activity of essential oil from of Ocimum ciliatum Hornem. The inhibitory effects of the essential oil were tested against 10 laboratory strains included Ralstonia solanacearum, Pseudomonas syringae pv. lachrymans, Pseudomonas syringae pv. syringae, Pseudomonas tolaasii, Xanthomonas oryzae pv. oryzae, Xanthomonas citri, Brenneria nigrifluens, Pantoea stewartii subsp. indologenes , Agrobacterium vitis and Rhodococcus fascians by using disc diffusion assay. GC and GC-MS analyses analysis revealed that the essential oil predominantly contains methyl chavicol (87.6%), methyl eugenol (2.6%) and 1,8-cineole (1.7%) that making this plant as a good source of methyl chavicol. The antibacterial test results showed the oil had antibacterial activity against all of the tested bacteria. According to the width of the inhibition zone, the most susceptible bacterium was Brenneria nigrifluens and the most resistant bacterium was Pseudomonas tolaasii. Furthermore, the lowest MIC values were obtained with the oil against Ralstonia solanacearum. The most bactericidal properties with the lowest MBC were observed against Xanthomonas citri strain.

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