Evaluation of Inhibitory Effect and Mechanism of Euphorbia Factor L3 against Phytophthora capsici

Abstract

Phytophthora capsici is a highly destructive phytopathogenic oomycete with a broad host range and is responsible for tremendous losses. Euphorbia factor L3 (EFL3) is a natural plant-derived compound that has been widely studied in medicine and cosmetic applications. In this study, the sensitivity of 105 P. capsici isolates to EFL3 was determined, and the biological activity and physiological effects of EFL3 against P. capsici were investigated. The median effective concentration (EC50) values for EFL3 inhibition mycelial growth and spore germination ranged from 0.66 to 8.94 μg/mL (mean, 2.96 ± 0.91 μg/mL) and 1.63 to 13.16 μg/mL (mean, 5.30 ± 1.64 μg/mL), respectively. EFL3 treatment resulted in cell wall and cell membrane damage of P. capsici, which was revealed by morphological and ultrastructural observations, propidium iodide (PI) and calcofluor white (CFW) staining, and measurements of relative conductivity as well as malondialdehyde (MDA) and glycerol contents. In addition, the contents of phospholipid and cellulose, which are the major components of cell membrane and cell wall, were significantly reduced following EFL3 treatment. Furthermore, EFL3 provided protective as well as curative efficacies against P. capsici on detached tomato leaves and pepper seedlings in vivo. These data show that EFL3 exhibits strong inhibitory activity against P. capsici, thereby suggesting that it could be an effective alternative for controlling P. capsici-induced diseases.

Antifungal activity of the botanical compound rhein against Phytophthora capsici and the underlying mechanisms

“…Meanwhile, rhein was also found to significantly damage the mycelial cell wall integrity of P. capsici , which was verified by AKP activity determination and a CFW staining assay. Similar results showing damage to the cell wall integrity have been reported in Geotrichum citri‐aurantii treated with peppermint essential oil or P. capsici treated with euphorbia factor L 3 28,29 . Moreover, the OM and TEM results indicated that the morphology and ultrastructure of mycelia were altered after treating P. capsici with rhein.…”

“…Several plant extracts exert antifungal functions by acting directly or indirectly on the cell membrane and cell wall of fungi, destroying the permeability of the cell membrane, damaging the integrity of the cell wall, and leaking important cell components 27,29 . Given the satisfactory antifungal activity of rhein against P. capsici , the antifungal mechanism of rhein was further investigated in this study.…”

“…Calcofluor white (CFW) staining was conducted to clarify the effect of rhein on cell wall integrity 29 . Mycelial plugs of P. capsici were cut and cultured in V8‐juice medium in a shaker (175 rpm) at 25 °C for 48 h. Then, rhein (0, 5, and 10 μg mL −1 ) was added to the medium.…”