Effects of Citrus sinensis (L.) Osbeck epicarp essential oil on growth and morphogenesis of Aspergillus niger (L.) Van Tieghem.

Essential oils from different plant parts are known for their antimicrobial activity but the antifungal effects of essential oil from Citrus sinensis (L.) Osbeck epicarp on growth and morphogenesis of Aspergillus niger has not been observed so far. The mycelial growth was inhibited at 2.5 and 3.0 microg/ml of oil in Potato Dextrose Broth and Agar medium, respectively. These concentrations were fungicidal under the test conditions. The fungitoxicity of oil did not change even at exposure to 100 degrees C and autoclaving. The main changes observed under light and scanning electron microscopy after oil treatment were loss of cytoplasm in fungal hyphae, and budding of hyphal tip. The hyphal wall and its diameter became markedly thinner, distorted and resulted in cell wall disruption. The flattened and empty hyphal tips bifurcated into bud like structures. GC-MS studies of the oil revealed the presence of 10 chemical constituents. Limonene has been found to be major component (84.2%).