Thymol Induces Cell Death of Fusarium oxysporum f. sp. niveum via Triggering Superoxide Radical Accumulation and Oxidative Injury In Vitro

Abstract

Fusarium oxysporum f. sp. niveum (FON) causes watermelon wilt that is one of the major disease-causing yield losses of watermelon. Sustainable development of agriculture requires controlling watermelon wilt disease with good environmental performance. One important approach is to identify environmental-friendly compounds with inhibitory activity against FON. Thymol is a plant-derived compound that is safe for ecology. Little is known about the application of thymol in agriculture. In this study, we studied the inhibitory activity of thymol against FON by using morphological, physiological, and histochemical approaches. Thymol significantly inhibited colony diameter of FON in a dose-dependent manner, with EC50 at 21 µg/mL. Thymol at 10, 21, and 35 µg/mL decreased the fresh weight of FON mycelia by 29.0%, 50.6%, and 69.5%, respectively. Microscopic observation revealed irregular damage and loss of shape of mycelia upon thymol exposure. Thymol induced the accumulation of superoxide radical in mycelial cells and accompanied increased activity of antioxidative enzymes (SOD, superoxide dismutase; CAT, catalase). Thymol induced membrane permeability was indicated by lipid peroxidation and electrolyte leakage (increased by 29–58%) in mycelial cells. These results suggested that thymol induced oxidative damage in mycelia, which may be one of the possible reasons for thymol-induced mycelial cell death observed with fluorescent detection. Thymol decreased the production of conidia and inhibited the germination of conidia. Thymol induced superoxide radical accumulation, lipid peroxidation, and cell death in conidia as well. All of these results revealed the inhibitory activity of thymol against FON, which may have resulted from the superoxide radical-induced oxidative injury in both conidia and mycelia of FON.

Evaluación in vitro y QSAR (Quantitative and Structure-Activity Relationship) de la actividad antifúngica de terpenoides obtenidos de aceites esenciales frente a Alternaria alternata y Fusarium oxysporum

“…However, essential oils and their constituents have other effects, such as forming reactive oxygen species, inhibiting efflux pumps, and causing the dysfunction of fungal mitochondria (59,60). In the case of F. oxysporum, thymol induces the accumulation of superoxide radicals with a consequent increase in the activity of antioxidant enzymes and lipid peroxidation (61).…”

The Impact of Biocontrol Bacteria on Cotton Resistance and Their Effects on Signaling Pathways Related to Defense Against Verticillium Wilt Infection

“…The collected mycelia were washed ve times with sterile water, vacuum-ltered for 15 minutes, and resuspended in 20 ml sterile water. The conductivity of the sterile water was measured every 10 minutes for 2 hours using a conductivity meter, with The nal conductivity determined after boiling the resuspended mycelia in sterile water for 5 minutes (Hao et al, 2023;Lin et al, 2023;Cai et al, 2023).…”