Chemical composition and antifungal activity of citrus and lemongrass essential oils in combination with cold storage regimes against Botrytis cinerea
Abstract: Postharvest diseases cause serious losses for the apple fruit industry in South Africa. The chemical composition of essential oils of lemon (Citrus limon), lime (Citrus aurantifolia) and lemongrass (Cymbopogan citratus) were analysed using gas chromatography (GC)-mass spectrometry (MS). The analysis exhibited that active components in essential oils of C. limon, C. aurantifolia and C. citratus agree with those found in literature. The analysis exhibited 45 components in essential oil of C. limon, with limonene and gamma-terpinene as the major compounds; C. aurantifolia included 20 components with limonene and gamma-terpinene as the most abundant compounds; while C. citratus revealed 27 components with geranial and neral as the major compounds. Direct contact and vapour phase methods were used to screen the antifungal activity of these essential oils against the major postharvest pathogen of apples caused by B. cinerea. Direct contact phase of lemongrass essential oil, mixtures of lemon and lemongrass and lime and lemongrass essential oils exhibited the strongest toxicity and completely inhibited the mycelial growth of B. cinerea for all concentrations tested at 20 °C, regular atmosphere and controlled atmosphere. Similar results were observed for mixtures of lemon and lemongrass and lime and lemongrass essential oils. Lemon and lime essential oils also showed antifungal activity but they were much less effective than lemongrass essential oil. In the case of the vapour phase method, all essential oil treatments significantly (P < 0.05%) controlled B. cinerea at all concentrations tested compared to control treatments. Mycelial growth of B. cinerea was inhibited by the tested essential oils in a dose-dependent manner. This study demonstrated that C. limon, C. aurantifolia and C. citractus essential oils in combination with cold storage regimes have a potential for the control of postharvest pathogen of apples caused by B. cinerea.