Essential oil of Tunisian plant: biopesticide applied in agricultural system

The use of plant-derived products in postharvest disease management may be a valid alternative to conventional chemical treatments (Pane et al., 2016). Unfavorable environmental conditions (such as salt and drought) increase production and accumulation of reactive oxygen species (ROS). Consequently, Tunisian plants have developed adaptive responses including the synthesis of specific bioactive molecules used for medical and nutritional purposes (Ksouri et al., 2012). In that context, the main objective of the present study was the identification of essential oils from Tunisian plants against the important plant pathogens, particularly in Europe.
The study began with the selection of endemic medicinal plant suspected to present antimicrobial properties. The essential oil was extracted by hydrodistillation using a Clevenger type apparatus (with a yield of 1.2%). The chemical composition of the essential oil obtained by hydro-distillation from the aerial parts was analyzed by GC/MS. Therefore, antifungal activity was evaluated against Fusarium culmorum, Fusarium oxysporum and Penicillium italicum, using ELISA microplates with a blocked randomized design, as described previously (Kouassi et al., 2012). In addition, the essential oil was then tested for their herbicidal activities in pre-emergence and post-emergence assays against three weeds species.
The chromatographic analysis showed a complex mixture where twenty compounds were identified accounting for 98.75 % of the total oil. Monoterpenes was represented by 71.73 %. The dominant monoterpenes are α Pinene (7.09%), 1,8-Cineole (54.6%) and Camphor (12.27%). Essential oil reduced significantly spores germination in a dose-dependent manner. Their fungistatic activity reached 100% at 0.6% against Fusarium oxysporum .
In the dose response bioassay, the essential oil reduced seed germination rate of Phalaris minor, Sylibum marianum and Trifolium incanatum. Seedling growth was measured by shoot and root lengths at day 7. At 0.5%, essential oil reduced 100% seed germination.
Post-emergence bioassays consisted in spraying essential oil at 3 concentrations (0.75, 2 and 3.4 %) at 2 leaves stage of three weeds species. Pelargonic acid was used as commercial positive control at 3.4%. At 0.75% and 2%, the essential oil do not show any sign of injury. However, only at 3.4 %, the spraying of essential oil showed visible injury ranging from wilting (after 1 day) and chlorosis (after 3 day) on Trifolium incanatum and Phalaris minor. After formulation, to enhance the distribution, the coverage and the penetration of the active molecules, the essential oil presented a high herbicidal activity.
In conclusion, this work allowed to open new perspectives on the application of Tunisian essential oil as Novel biocontrol strategies against damageable plant pathogens and weeds.