Abstract
Thymol is a natural plant-derived compound that has been widely used in pharmaceutical and food preservation applications. However, the antifungal mechanism for thymol against phytopathogens remains unclear. In this study, we identified the antifungal action of thymol against Fusarium graminearum, an economically important phytopathogen showing severe resistance to traditional chemical fungicides. The sensitivity of thymol on different F. graminearum isolates was screened. The hyphal growth, as well as conidial production and germination, were quantified under thymol treatment. Histochemical, microscopic, and biochemical approaches were applied to investigate thymol-induced cell membrane damage. The average EC50 value of thymol for 59 F. graminearum isolates was 26.3 μg·mL−1. Thymol strongly inhibited conidial production and hyphal growth. Thymol-induced cell membrane damage was indicated by propidium iodide (PI) staining, morphological observation, relative conductivity, and glycerol measurement. Thymol induced a significant increase in malondialdehyde (MDA) concentration and a remarkable decrease in ergosterol content. Taken together, thymol showed potential antifungal activity against F. graminearum due to the cell membrane damage originating from lipid peroxidation and the disturbance of ergosterol biosynthesis. These results not only shed new light on the antifungal mechanism of thymol, but also imply a promising alternative for the control of Fusarium head blight (FHB) disease caused by F. graminearum.
Highlights
The filamentous ascomycete Fusarium graminearum Schwabe is a ubiquitous plant pathogen causing Fusarium head blight (FHB) in cereals
The EC50 values of thymol for these isolates ranged from 22.53 to 51.76 μgmL1, with a mean value of 26.3 μgmL1 (Figure 1b). These results indicated that thymol had a severe adverse effect on the growth of F. graminearum
The effective control of FHB disease caused by F. graminearum is a big challenge worldwide [34]
Summary
The filamentous ascomycete Fusarium graminearum Schwabe (teleomorph: Gibberella zeae) is a ubiquitous plant pathogen causing Fusarium head blight (FHB) in cereals. In China, FHB is an economically important disease, which has spread wildly from frequently occurring areas in eastern costal regions to the emerging outbreak area in northern and western wheat-growing regions [2,3,4]. Molecules 2016, 21, 770 with resistance to FHB would seem to be the most promising approach to control this disease, but highly-resistant cultivars have not yet been developed for commercialization [5]. FHB has been mainly controlled with chemical fungicides [6]. Benzimidazole (e.g., carbendazim) and triazole (e.g., tebuconazole) fungicides have been extensively applied to control FHB in China for many years [7,8]. Chemical fungicide residues with high toxicity pose a potential risk to the environment and human health
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