Anthracnose caused by Colletotrichum gloeosporioides has been destructive during pepper fruit production in outdoor fields in Korea. In vitro antifungal activities of 15 different plant essential oils or its components were evaluated during conidial germination and mycelial growth of C. gloeosporioides. In vitro conidial germination was most drastically inhibited by vapour treatments with carvacrol, cinnamon oil, trans-cinnamaldehyde, citral, p-cymene and linalool. Inhibition of the mycelial growth by indirect vapour treatment with essential oils was also demonstrated compared with untreated control. Carvacrol, cinnamon oil, trans-cinnamaldehyde, citral and eugenol were among the most inhibitory plant essential oils by the indirect antifungal efficacies. Plant protection efficacies of the plant essential oils were demonstrated by reduced lesion diameter on the C. gloeosporioides-inoculated immature green pepper fruits compared to the inoculated control fruits without any plant essential oil treatment. In planta test showed that all plant essential oils tested in this study demonstrated plant protection efficacies against pepper fruit anthracnose with similar levels. Thus, application of different plant essential oils can be used for eco-friendly disease management of anthracnose during pepper fruit production.

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Phospholipases hydrolyze phospholipids into fatty acids and other lipophilic substances. Phospholipid signaling is crucial for diverse cellular processes in plants. However, the precise role of phospholipases in plant cell death and defense signaling is not fully understood. Here, we identified a pepper (Capsicum annuum) patatin-like phospholipase (CaPLP1) gene that is transcriptionally induced in pepper leaves by avirulent Xanthomonas campestris pv. vesicatoria (Xcv) infection. CaPLP1 containing an N-terminal signal peptide localized to the cytoplasm and plasma membrane, leading to the secretion into the apoplastic regions. Silencing of CaPLP1 in pepper conferred enhanced susceptibility to Xcv infection. Defense responses to Xcv, including the generation of reactive oxygen species (ROS), hypersensitive cell death and the expression of the salicylic acid (SA)-dependent marker gene CaPR1, were compromised in the CaPLP1-silenced pepper plants. Transient expression of CaPLP1 in pepper leaves induced the accumulation of fluorescent phenolics, expression of the defense marker genes CaPR1 and CaSAR82A, and generation of ROS, ultimately leading to the hypersensitive cell death response. Overexpression (OX) of CaPLP1 in Arabidopsis also conferred enhanced resistance to Pseudomonas syringae pv. tomato (Pst) and Hyaloperonospora arabidopsidis infection. CaPLP1-OX leaves showed reduced Pst growth, enhanced ROS burst and electrolyte leakage, induction of the defense response genes AtPR1, AtRbohD and AtGST, as well as constitutive activation of both the SA-dependent gene AtPR1 and the JA-dependent gene AtPDF1.2. Together, these results suggest that CaPLP1 is involved in plant defense and cell death signaling in response to microbial pathogens.