Expression profiling of PR genes and the protective effect of Pseudomonas syringae, Arthrospira platensis and Elettaria cardamomum in tomato (Solanum lycopersicum) under diverse biotic stress conditions

Abstract Pathogenesis-related (PR) genes play a central role in plant defense, yet their expression can vary widely under natural conditions. This study analyzed the expression patterns of two key PR genes PR1 ( SL_PR1a2 ) and PR10 ( Sol_1_PR_10_4.02 ), in tomato following treatments with Arthrospira platensis , Elettaria cardamomum , and their combinations with Pseudomonas syringae . Gene expression was quantified using qRT-PCR under both field conditions (1 day post inoculation and 1 week post inoculation) and laboratory conditions (3 days post inoculation). Bar-graph analysis revealed that A. platensis and E. cardamomum induced PR genes with treatment-specific and time-dependent effects, while P. syringae alone suppressed expression. Laboratory assays showed strong, dose-dependent induction by E. cardamomum and consistent activation by A. platensis . Time-course curves and heat maps demonstrated that laboratory conditions support stable and robust PR-gene induction , whereas field responses are heterogeneous and less predictable, reflecting environmental fluctuations. These findings highlight the potential of A. platensis and E. cardamomum as natural defense enhancers, particularly in controlled environments, and provide insight into optimizing biostimulant-based strategies for disease management in tomato.