ETD

• botanicals
• Colletotrichum spp.
• essential oils
• Fusarium spp.
• organic seed coating
• seed-borne
• soil-borne

Introduction
Sowing healthy seeds for agricultural production can protect plant seedlings from infection, mainly caused by seed-borne and soil-borne pathogens. Synthetic fungicides are the most used tool to manage fungal diseases. However, there is an increased disquiet about their application, while environmentally friendly alternatives are becoming gradually addressed to reduce seed contamination by pathogens, especially in organic agriculture. In this thesis, six essential oils (Melaleuca alternifolia, Eucalyptus globulus, Citrus bergamia, Lavandula angustifolia, Origanum vulgare and Cinnamomum verum) are tested for organic seed-coating against Fusarium oxysporum (f. sp. ciceri and pisi), F. solani f. sp. phaseoli, Colletotrichum lupini and C. chrysanthemi on leguminous and innovative species.
Materials and methods
Two in vitro tests were performed to assess the inhibition of fungal growth by chosen essential oils (EOs) at 1.0% in an aqueous solution containing 0.1% Tween 20. Antifungal activity due to diffusible compounds was performed directly on PDA, while the effect of volatile compounds was assessed on PDA plates containing a filter paper applied on the lid added with the EOs solution. In vivo phytotoxicity tests on seeds allowed to select the two most performing EOs not affecting seed germination (in sand, 20 seeds per tray, 4 replicates). Finally, the selected EOs were applied on seeds sown in soil inoculated with the pathogens (20 seeds per tray, 3 replicates). Data were submitted to one-way ANOVA, followed by F-test to determine significant differences (p<0.05).
Results and conclusions
In vitro tests showed that, among the six EOs, oregano and cinnamon exhibited the strongest fungal growth inhibition, especially due to volatiles. With respect to phytotoxicity, the two EOs (1%) do not impair seed germination and early growth, although some variability was observed. Antifungal trials revealed negligible activity against the fungi, afterwords suggesting that EOs bioactivity are mainly associated with their volatile compounds, whose efficacy is significantly reduced once applied in soil. The promising in vitro performances of the two EOs highlights their potential as organic seed-coating treatments. Evaluating their long-term effectiveness in field conditions and exploring possible synergistic effects with other organic treatments will be essential to translate the promising laboratory outcomes into practical and sustainable agricultural solutions.