Essential oils from Dittany of Crete for the control of botrytis cinerea on tomato, eggplant and pepper fruits

The degree of postharvest losses of fruit and vegetables due to attack by microorganisms worldwide is significant. In addition, the use of chemicals increases consumer concerns regarding food safety. Recent studies indicate that exploitation of natural compounds such as essential oils (EOs) may provide an alternative and friendlier way for the preservation of fresh produce. In this research project the efficacy of Origanum dictamnus L. essential oils (EOs) (a medicinal-aromatic plant of Crete) for the control of B. cinerea, a common postharvest pathogen of three economically important Cretan vegetables, tomato, pepper and eggplant was examined. Pathogen development in culture medium or on fruits was evaluated after treatment with dittany EO (0, 50, 100, 250 ppm) in vitro and in situ when stored at 12°C and 95% RH during or following exposure to EO volatiles. The impacts of short term exposure of B. cinerea to volatiles on growth and sporulation were also studied. Fungal development in vitro was completely inhibited by the continued application of 100 or 250 ppm of EO volatiles while inhibitory effects were also marked by lower EO concentration and short time of exposure. In inoculated fruits the 50 ppm of EO application resulted in suppressed disease development by reduced lesion growth and fungal sporulation, where increasing EO concentration led to greater effects. Pre-exposure of fruits to volatiles before fungal inoculation revealed reduced lesion growth, indicating that dittany EO probably caused induced resistance of fruits against the pathogen. Moreover, EO application did not affect quality-related characteristics of fruits while skin lightness and pulp lightness of eggplant fruits was improved under the presence of dittany volatiles. Overall, the results suggest that dittany EO volatiles may be considered as an alternative food preservative treatment, significantly reducing or eliminating B. cinerea infection during fruit storage and perhaps also in transit.