Mechanisms of Litsea cubeba essential oil in the control of Colletotrichum scovillei in pepper (Capsicum annuum L.): Cell membrane/wall perspective

Although Litsea cubeba essential oil (LCEO) is widely used for against fungi, antifungal mechanism of it is not fully understood. In the study, antifungal potential and mechanism of LCEO on Colletotrichum scovillei, the main pathogen fungi caused pepper anthracnose, were studied. Results of gas chromatograph-mass spectrometry (GC-MS) showed that citral (67.37%) and d-Limonene (11.72%) were the major components of LCEO. LCEO was effective in inhibiting germination of C. scovillei spores, and the minimum inhibitory concentration (MIC) was 0.60 mg mL −1. To determine influence of LCEO on cell membrane integrity and permeability of C. scovillei, SEM observation, OD260 nm (nucleic acids), OD280 nm (proteins), extracellular electric conductivity, cell membrane permeability (propidium iodide, PI), cell wall integrity (calcofluor white, CFW), malondialdehyde (MDA) content and ergosterol content were analyzed. Spores exposed to LCEO were partly deformed, collapsed, shrunken and shriveled. The OD260 nm, OD280 nm and the extracellular electric conductivity of LCEO treatment group increased by 2.0, 1.5 and 1.2 times, respectively, at 12 h after treatment of LCEO (0.6 mg mL−1). Besides, high accumulation of MDA content indicated that LCEO significantly enhanced membrane lipid peroxidation. Moreover, LCEO induced a decrease in ergosterol content of C. scovillei. These findings suggest that LCEO exhibited potent inhibitory activities against C. scovillei, and the cell membrane permeability and cell wall integrity of C. scovillei treated by LCEO were significantly destroyed.