Intact salicylic acid signalling is required for non-host resistance of potato against the hemibiotroph pathogen Phytophthora capsici

Non-host resistance (NHR) broadly protects plants from most pathogens, but the role of salicylic acid (SA) signaling in NHR against hemibiotrophic Phytophthora capsici remains unclear. Here, we show that SA is essential for NHR by using SA-deficient (NahG) potato lines. The relsut showed that NahG plants developed significantly larger P. capsici lesions than wild-type controls. Transcriptomic analysis identified 3,363 differentially expressed genes (DEGs) in NahG plants, characterized by systemic downregulation of SA pathway genes and pathogenesis-related (PR) genes, contrasted by upregulation of photosynthesis-related genes and auxin (IAA)/abscisic acid (ABA) signaling components. Jasmonic acid (JA) signaling was activated via suppression of JAZ repressors and induction of JAR1/MYC2. Hormone profiling revealed reduced levels of SA, JA, JA-isoleucine (JA-Ile), IAA, and ABA in NahG lines. Critically, Virus-induced gene silencing (VIGS) demonstrated that silencing WRKY53 significantly enhanced disease resistance, whereas silencing ERF1B accelerated disease progression in plants. Collectively, these findings demonstrate that intact SA signaling coordinates defense gene expression, hormonal crosstalk, and metabolic homeostasis, making it indispensable for potato NHR against P. capsici.