Yongjian Fan

Antifungal activity of eugenol against Botrytis cinerea

The antifungal properties of eugenol were tested against ten plant pathogenic fungal species and detailed studies were conducted regarding in vitro activity of eugenol on Botrytis cinerea. The EC50 value of eugenol on mycelial radial growth of B. cinerea was 38.6 μg/mL; however, eugenol had no bioactivity against conidia germination. B. cinerea hyphae treated with eugenol showed strong propidium iodide fluorescence in the cytosol. Eugenol increased the concentration of potassium ion and cellular materials in the medium. Furthermore, light and scanning electron microscopy observations on hyphae exposed to eugenol revealed considerable morphological alterations in hyphae, such as cytoplasmic coagulation, vacuolation, and hyphal shriveling. Eugenol induced the generation of H2O2 and increased free Ca2+ in the cytoplasm. These results strongly support the idea that the antifungal activity of eugenol is due to membrane binding and permeability alteration, leading to destabilization and disruption of the plasma membrane.

Efficacy of osthol, a potent coumarin compound, in controlling powdery mildew caused by Sphaerotheca fuliginea

The efficacy of osthol, a natural coumarin compound, in controlling powdery mildew was evaluated in 2004–2005 in Anhui and Hebei Provinces of China. In both years, the treatments (osthol 15.0 and 18.0 g ai ha− 1) showed a stable control efficiency of 75.42, 81.24% and 76.36, 84.84%, respectively, at the Institutes of Plant Protection of Hebei Academy of Agricultural Sciences. In field experiments, osthol was as effective as difenoconazole in controlling powdery mildew and was more effective than triadimefon against Sphaerotheca fuliginea. Protection was expressed as a significant reduction (up to 87% compared with the control) in the mildewed leaf area in young pumpkin plants. Osthol strongly inhibited spore germination and mycelial growth of S. fuliginea in vitro, damaged the cell wall and the organelles of the pathogen. At 48 h after incubation, 50 μg ml− 1 osthol could completely inhibit spore germination. These findings suggested that the effect of osthol on powdery mildew may be associated with the direct fungitoxic property against the pathogen. We conclude that osthol would be an attractive natural compound for practical agronomic use against powdery mildew.

Antifungal activity of the osthol derivative JS-B against Phytophthora capsici.

JS-B (C12H10O3) is a derivative compound of osthol. The antifungal properties of JS-B were tested against 10 economically important plant pathogens. JS-B was effective in inhibiting the mycelial growth of Phytophthora capsici, and its inhibition on different stages of the life cycle of P. capsici was observed. The 50% effective concentration (EC50) of JS-B on mycelial dry weight and zoospore germination of P. capsici was 43.74 and 86.03 μg/ml, respectively. The rupture of released zoospores induced by JS-B was reduced by the addition of 100 mM glucose. The ultrastructural study showed that JS-B caused destruction of most of the mitochondrions, the concentration of cell nuclear, and the existing vesicles. When compared with dimethomorph, the activity of JS-B on P. capsici was determined under pot conditions. The result showed that JS-B has a curative effect on pepper blight.