tThis study was designed to examine the chemical composition and the in vitro antibacterial activity ofessential oil of Ocimum ciliatum Hornem. The inhibitory effects of the essential oil were tested againstten phytopathogenic strains, including Ralstonia solanacearum, Pseudomonas syringae pv. lachrymans, P.syringae pv. syringae, P. tolaasii, Xanthomonas oryzae pv. oryzae, Xanthomonas citri, Brenneria nigrifluens,Pantoea stewartii subsp. indologenes, Agrobacterium vitis, and Rhodococcus fascians using disk diffusionassay. GC and GC–MS 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 methylchavicol or estragole. The antibacterial test results indicated the oil had antibacterial activity against allof the tested bacteria. According to the width of the inhibition zone, the most susceptible bacterium wasB. nigrifluens and the most resistant bacterium was Pseudomonas tolaasii. Furthermore, the lowest MICvalues were obtained from the essential oil of the plant against R. solanacearum. In addition, the mostbactericidal property of the essential oil from O. ciliatum with the lowest MBC was observed against X.citri strain.

Keywords