Inhibition efficacy of Tetradium glabrifolium fruit essential oil against Phytophthora capsici and potential mechanism

Phytophthora capsici is a notorious pathogen capable of infecting various host plants and causing serious threats to agriculture worldwide. Tetradium glabrifolium fruit essential oil (TFO) is widely utilized in traditional Chinese medicine treatment, but its antimicrobial activity is unknown. In this study, we first investigated the inhibitory efficacy of TFO against P. capsici and found TFO strongly inhibited the development of phytophthora blight on pepper by in vivo inoculation assay. Second, we found TFO could significantly suppress vegetative and reproductive growth of P. capsici in vitro. Microscope observations indicated that TFO destroyed the mycelial morphology and cellular ultrastructure of P. capsici. Additionally, TFO could damage the cell membrane integrity of the pathogen, leading to cellular leakages of intercellular contents of P. capsici. Third, TFO could enhance the activities of defence-related enzymes in pepper fruits during pathogen infection. Finally, we identified the chemical composition of TFO by GC-MS analysis and demonstrated three abundant components (D-limonene, β-elemene, and 2-tridecanone) contributed to the antifungal activity of TFO. Together, out results revealed that TFO had outstanding inhibitory efficacy against P. capsici, and uncovered its potential antifungal mechanism. This study would propose the application of TFO as an efficient alternative approach for controlling phytophthora blight.