Antibacterial effect of some essencial oils on rice pathogen Xanthomonas oryzae pv. oryzae

Bacterial blight disease of rice, caused by Xanthomonas oryzae pv. oryzae, is one of the most important diseases of rice worldwide. Incidence of this disease has been reported in Iran. In present study, antibacterial effects of some medicinal plants of Kohgiluyeh and Boyer-Ahmad province on this bacterium as well as on Pseudomonas fluorescens CHA0 was investigated. Antimicrobial effect of essential oils of Thymus daenensis, Rosmarinus officinalis, Foeniculum vulgar, Mentha spicata, Mentha piperita and Pelargonum graveolens was determined by agar diffusion method, under laboratory condition. Minimal inhibitory concentration (MIC) and Minimal bactericide concentration (MBC) of essential oils were also determined. The results showed that, at the concentrations of 4 and 100 mg/ml, the essential oil of T. daenensis had the highest antibacterial effect and at the concentration of 4 mg/ml, Mentha spicata had the lowest antibacterial effect. At the concentration of 1 mg/ml, essential oils of Mentha piperita, Mentha spicata and Foeniculum vulgar showed the most antibacterial activity. It was found that Xanthomonas oryzae pv. oryzae was the most sensitive to Thymus daenensis with MIC of 0.122 mg/ml and MBC of 0.245 mg/ml, while Pseudomonas fluorescens CHA0 was the most sensitive to Foeniculum vulgar with MIC of 1.95 mg/ml and MBC of 3.90 mg/ml.