Aromatic sesquiterpenes isolated from high-trichome sun-cured tobacco as potential activators for powdery mildew

Background : Powdery mildew is a fungal disease threatening major global crops such as tobacco, rice, and grapes. Pathogens cause severe yield losses by disrupting photosynthesis and inducing premature plant senescence. Traditional chemical fungicides face challenges of drug resistance, environmental pollution, and health risks, urgently requiring low-toxic and sustainable alternatives. This study aims to identify novel sesquiterpenoids against powdery mildew from the high-tichome sun-cured tobacco variety "Huize Liuye" and elucidate their antibacterial mechanisms. Results : Chemical studies led to the isolation and identification of seven novel (1-7) and four known (8-11) aromatic sesquiterpenes. Compounds 5 and 6 represent the first examples of sesquiterpenes containing a 4-methylfuran-2-yl moiety, while compound 7 is a rare sesquiterpene featuring a benzo[ c ]azepin-1-one skeleton. Antifungal assays revealed that compound 7 exhibited the highest inhibitory activity against G. cichoracearum with an inhibition rate of 86.2% ± 5.6, surpassing the positive control carbendazim (83.5% ± 6.0). Analyses using microscopy and scanning electron microscopy (SEM) demonstrated that compound 7 disrupts conidial morphology and inhibits hyphal development. Transcriptomic and metabolomic studies further demonstrated that compound 7 activates plant defense pathways, including salicylic acid（SA）- and jasmonic acid (JA)-mediated signaling, and enhances biosynthesis of antifungal secondary metabolites. Molecular docking confirmed strong interactions between compound 7and tubulin proteins, which also supported its efficacy. Additionally, compound 7 also showed activity against Podosphaera pannosa in rose. Conclusion : This study establishes Huize Liuye tobacco as a valuable resource for natural sesquiterpene-based antifungal agents, with compound 7 demonstrating exceptional potential as an efficient fungicide due to its unique chemical structure, high antifungal activity, and broad-spectrum efficacy. The findings provide a theoretical basis for utilizing tobacco byproducts, such as trichomes, as renewable sources for biopesticide development, thereby underscoring the ecological value of high-trichome crops in sustainable agriculture as substitutes for synthetic chemicals.