A novel plant immune inducer esculetin activates systemic acquired resistance against Ralstonia solanacearum via the SA signaling pathway

BACKGROUND: Ralstonia solanacearum poses a severe threat to global agriculture due to its broad host range, high dispersal capacity, and limited chemical control options. Plant immune inducers provide an effective strategy for controlling bacterial wilt disease. RESULTS: This study demonstrated a natural-derived compound esculetin (ES) serves as a novel plant immune inducer against tobacco bacterial wilt. Foliar application of ES exhibits considerable control effect on tobacco bacterial wilt, with control efficacy is high as 45.41%-68.69%, significantly higher than positive control treatment-benzothiadiazole (BTH). ES activates systemic acquired resistance (SAR) by upregulating transcriptional level of pathogenesis-related (PR) genes, inducing reactive oxygen species (ROS) burst, enhancing defense-related enzyme activity and salicylic acid (SA) accumulation. Transcriptomic analyses reveal that ES induces expression of mitogen-activated protein kinase (MAPK) signaling pathways, SA biosynthesis, phenylpropanoid pathway and brassinosteroid biosynthesis pathway. Furthermore, ES confers broad-spectrum resistance against other diseases like tobacco target spot, tobacco mosaic virus (TMV), wildfire disease and tobacco black shank. CONCLUSION: The study reveals a novel plant immunity inducer ES that confers broad-spectrum resistance against R. solanacearum by activating the SA-mediated SAR pathway, which provides a sustainable application of ES on bacterial wilt and other plant diseases in the future. © 2026 Society of Chemical Industry.