Revealing the Mechanisms for Linalool Antifungal Activity against Fusarium oxysporum and Its Efficient Control of Fusarium Wilt in Tomato Plants

Abstract

<i>Fusarium oxysporum f.</i> sp. <i>radicis-lycopersici</i> (<i>Forl</i>) is a destructive soil-borne phytopathogenic fungus that causes Fusarium crown and root rot (FCRR) of tomato, leading to considerable field yield losses. In this study, we explored the antifungal capability of linalool, a natural plant volatile organic component, against <i>Forl</i> and its role in controlling FCRR symptoms in tomatoes. Our results showed that <i>Forl</i> mycelial growth was inhibited by the linalool treatment and that the linalool treatment damaged cell membrane integrity, enhanced reactive oxygen species levels, depleted glutathione, and reduced the activities of many antioxidant enzymes in <i>Forl</i>. Transcriptomic and proteomic analyses demonstrated that linalool also downregulated metabolic biosynthetic pathways at the transcript and protein levels, including redox, transporter activity, and carbohydrate metabolism in <i>Forl</i>. Moreover, linalool significantly decreased the expression of many <i>Forl</i> pathogenic genes, such as cell wall degrading enzymes (CWDEs) and G proteins, which is likely how a <i>Forl</i> infection was prevented. Importantly, exogenously applied linalool activated the salicylic acid (SA) and jasmonic acid (JA) defensive pathways to improve disease resistance and relieved the negative effects of <i>Forl</i> on plant growth. Taken together, we report that linalool is an effective fungicide against <i>Forl</i> and will be a promising green chemical agent for controlling FCRR.