Phytotoxic volatilome from the endophytic fungus Hypoxylon anthochroum strain Smeg4: Temporal dynamics and mitochondrial disruption as a promising herbicidal mechanism.

This study provides a comprehensive temporal characterization of the volatilome produced by the endophyte Hypoxylon anthochroum Smeg4 and evaluates its phytotoxic activity against four weed species. VOCs diversity and abundance were contingent on culture age, following four distinct metabolic phases (Groups 1-4). During the preliminary stage (days 1-2, Group 1), monoterpenes predominated with low diversity (11-17 compounds). A chemical shift occurred on day 3 (Group 2), followed by the prevalence of eucalyptol and the first detection of esters, such as ethyl ethanoate, on day 4. Peak metabolic richness was attained between days 5 and 9 (Group 3), with 38 compounds from six chemical families, including the exclusive detection of 2,5-dimethylfuran, ethyl propionate, β-pinene, α-pinene, isocaryophyllene, and 7-epi-α-selinene. This peak coincided with the highest phytotoxic potential, significantly inhibiting germination, root growth, and respiration in Amaranthus hypochondriacus and Medicago sativa. In the late phase (days 10-20, Group 4), diversity and abundance declined. Mechanism of action assays revealed that VOCs mixtures from this phase trigger an early energetic collapse by inhibiting basal mitochondrial respiration and severely damaging membrane potential (ΔΨm). These results demonstrate that H. anthochroum Smeg4 dynamically modulates its core volatilome to generate synergistic mixtures with species-specific phytotoxicity, positioning it as a promising source for mitochondrial-targeted bioherbicides.