Inhibitory effect of some medicinal plants' essential oils on postharvest fungal disease of citrus fruits

Misuse of chemical biocides for controlling pest and disease has drawn the attention of policy makers in to the potential of natural substances as an alternative. One new and safe method to control pests and diseases is use of essential oils from medicinal plants. In the present investigation, inhibition of radial growth and spore germination of important postharvest fungi (Penicillium italicum, P digitalum and Alternaria citri) exposed to different concentrations of essential oils of some medicinal plants (Thymus vulgaris, Mentha piperita, Satureja hortensis, Cuminum cyminum and Trachyspermum copticum) were studied. Concentrations of essential oils used were 250, 500 and 1000 mg/L. Radial growth of P italicum was completely inhibited by Th. vulgaris (500 mg/L), S. hortensis and T copticum (1000 mg/L). Radial growth of P italicum exposed to C cyminum and M. piperita essential oil (1000 mg/L) was decreased (57.17% and 36.8%, respectively). Radial growth of P digitatum was completely inhibited by Th. vulgaris, T copticum (500 mg/L) and S. hortensis (1000 mg/L). Radial growth of R digitatum exposed to essential oils of C. cyminum and M. piperita were decreased 22.8% and 12.15%, respectively. A. citri's radial growth was completely inhibited by Th. vulgaris (250 mg/L), T copticum and S. hortensis (500 mg/L), C cyminum (1000 mg/L). M. piperita essential oils (1000 mg/L) decreased radial growth of A. citri to be 59.44%. Therefore, the inhibitory potency of essential oils on the postharvest disease of citrus fruits was as Th. vulgaris> T copticum> S. hortensis> C cyminum> M. piperita and the extent of inhibition of fungal growth depended on t concentration used. These results indicate that these compounds could substitute for chemical fungicides as postharvest treatments since they are natural and not toxic to humans, and it is necessary to focus on practical application of essential oils to inhibit postharvest pathogen growth.