Citral‐amino‐oligosaccharide Schiff base induces plant systemic acquired resistance against tobacco mosaic virus

BACKGROUND: Chitosan oligosaccharide is the most extensively utilized elicitor in agricultural applications, demonstrating diverse biological activities. Its combination with other elicitors can enhance efficacy. However, challenges such as incompatibility with alkaline pesticides remain. Structural modification presents an effective strategy to address this limitation. RESULT: In this study, Citral-amino-oligosaccharide Schiff base (CAOS) was prepared and found to exhibit significant anti-TMV activity. Its protective, inactivation and curative activities (at 0.9 mg/L) reached 86.32%, 57.62%, and 49.52%, respectively, significantly outperforming the positive control, chitosan oligosaccharide. Investigation into its antiviral mechanism revealed that CAOS (0.9 mg/L) induced the overexpression of related defense enzymes (SOD, CAT, POD, PAL) in tobacco, and upregulated the expression of pathogenesis-related (PR) proteins, the key reactive oxygen species (ROS) burst gene RBOHB, and the chlorophyll synthesis-related gene POR1. Hypersensitive response (HR) results indicated the appearance of hypersensitive necrotic lesions after treatment with high concentrations of CAOS. Furthermore, CAOS induced resistance in crops against plant pathogenic fungal diseases. CONCLUSION: This study is the first to report on the significant anti-TMV activity of CAOS. Its antiviral mechanism involves inducing the overexpression of disease resistance-related genes, triggering a ROS burst, activating the regulation of related defense enzymes, and consequently activating the plant's Systemic Acquired Resistance (SAR), thereby enhancing the plant's disease resistance capability. CAOS is easily prepared, highly active, has a long duration of effect, and is broad-spectrum, demonstrating potential for development as a novel plant immune activator. © 2026 Society of Chemical Industry.