Antioomycete Activity and Mechanism of Territrem B, against Phytophthora capsici in Prevention of Phytophthora Blight

Phytophthora blight, caused by the oomycete pathogen Phytophthora capsici (P. capsici), is one of the most destructive diseases in the production of solanaceous and cucurbitaceous vegetable crops. In this study, a meroterpenoid, territrem B (TEB), exhibited significant antioomycete activity against P. capsici, with an EC₅₀ value of 22.96 μg/mL. In vitro and in vivo experiments demonstrated that TEB effectively suppressed the occurrence and spread of Phytophthora blight, significantly destroyed the cell membrane permeability and integrity of P. capsici, damaged its morphology and ultrastructure, and enhanced the defensive capacity of pepper plants. Physiological assays revealed that TEB increased the levels of MDA, decreased soluble protein content, inhibited the activities of antioxidant enzymes, and increased accumulation of reactive oxygen species and subsequent lipid peroxidation. A transcriptome assay revealed that TEB may target the amino acid synthesis, lipid metabolism, and cellular energy metabolism. This interference led to increased accumulation of reactive oxygen species and subsequent lipid peroxidation, ultimately inhibiting fungal growth. These results suggested that TEB could effectively combat diseases caused by P. capsici and had the potential for development into a novel oomyceticide for phytophthora blight management.