Rosemary extract primes cultivar-dependent defense responses in potato against pathogen attack

Potato ( Solanum tuberosum L.) is a major global food crop increasingly threatened by pathogens such as Potato virus X (PVX) and Phytophthora infestans . Priming with plant extracts, including rosemary aqueous extract (ARE), provides a sustainable strategy to enhance crop immunity. Here, constitutive and ARE-induced defense responses were analyzed across four commercial cultivars: Innovator, Kennebec, Spunta, and Frital-INTA. ¹ H NMR metabolomic profiling combined with defense gene expression analysis under non-infected conditions revealed cultivar-specific signatures, suggesting that basal metabolism and genetic background influence pathogen susceptibility and can be selectively tuned by ARE application. Subsequent infection assays with PVX and P. infestans validated these differential responses, identifying Innovator as more resistant and Spunta as more susceptible. Crucially, ARE pre-treatment significantly enhanced defense responses, particularly in susceptible cultivars. This priming effect resulted in a marked reduction in PVX accumulation and a decrease in P. infestans lesion size. These findings extend the established efficacy and sustainability of ARE to potato cultivation, demonstrating its capacity to act as a potent priming agent. Specifically, our results show that ARE reinforces potato immunity by integrating and amplifying both constitutive and inducible defense mechanisms, further highlighting its position as a versatile bioprotective tool for crop disease management