Effect of Citrus Stubborn Disease (Spiroplasma Citri) on Chemical Composition of Orange (Citrus Sinensis (L) Osbeck) Essential Oil Fruits

The effect of Citrus stubborn disease (CSD), caused by Spiroplasma citri, on chemical composition and antimicrobial activities of the essential oils of (Citrus sinensis(L) Osbeck) was studied. The results showed that the essential oil extracted from both healthy and Citrus fruit infected by the stubborn disease did not have the same physicochemical characteristics, but have identical chemical composition, with octanal, beta-phellandrene, d-limonene, 1 r-alpha pinene, and d-limonene as major compounds. The infected fruits contained new toxic compounds (2-cyclohexen-1-ol, 2-methyl-5-(1-methylethenyl)-cis, decanal, trans-p-mentha-2, 8-dienol, 2-cyclohexen-1-ol, and, 1-methyl-4-[1-methy-4-(1-methyletheyl)]-cis), at low concentrations (<1%). Both essential oils showed very interesting antibacterial activity against Escherichia coli ATCC 25922,Staphylococcus aureus ATCC 25923, and Pseudomonas aeruginosa ATCC 27853. However, they did not exert any antifungal activity against Botrytis cinerea. The minimum inhibitory concentration (MIC) for the bacterial strains, which were sensitive to the essential oil extracted from both infected and uninfected C. sinensis, was of 4 mu L and 32 mu L/mL, respectively.