Antifungal Activity of Fresh and Stored Olive Mill Wastewater (OMW) and Its Ethyl Acetate Extract against Plant Pathogens Fungi

Olive mill wastewater (OMW) has serious environmental problems considering its high organic matter, especially its phenolic compounds. The OMW application in crop protection is an alternative environmentally eco-friendly method reducing the chemicals pesticides impact on human health and environment. The present work aimed to study the antifungal activity of fresh and stored OMW and its ethyl acetate extract against phytopathogenic fungi: Syncephalastrum racemosum (S. racemosum), Paramyrothecium roridum (P. roridum), Fusarium oxysporum (F. oxysporum) and Verticilium dahlia (V. dahlia). The OMW was stored at 25 and 45 °C for 3 months. Fresh and stored OMW were used non-sterile, sterile and centrifuged. Phenolic and flavonoid compounds were extracted and identified by HPLC analysis. High inhibition of studied fungi was shown by fresh OMW and its derivative compounds, while OMW storage, sterilization, and centrifugation increased mycelium growth of studied fungi, especially S. racemosum that showed a relative resistance against stored OMW effect and its ethyl acetate extract. Under storage conditions, some phenolic and flavonoid compounds disappeared (resorcinol and vanillic acid), while the concentration of other compounds increased (gallic acid, chlorogenic acid and quercetin). This work highlighted the ability to use fresh OMW as a bio-agent to protect plants from fungi diseases.