Induced Resistance Against Tuta absoluta in Tomato Cultivars Using Eco-friendly Plant Growth Regulators in Egypt

Abstract

The South American tomato pinworm, Tuta absoluta, represents a severe threat to tomato production in Egypt, capable of causing up to 100% yield loss and devastating economic damage, a challenge intensified by climate change and escalating insecticide resistance. This study aimed to evaluate the efficacy of eco-friendly plant growth regulators (PGRs) - Salicylic acid, Benzyladenine, and Kinetin - as elicitors of induced resistance against T. absoluta across three distinct tomato cultivars: Hybrid Super Strain B, Baladi, and Castle Rock. A split-split-plot randomized complete block design was employed to assess infestation levels over a 3-week period. We first characterized the constitutive (pre-treatment) biochemical baseline of the three cultivars by measuring primary nutrients, proteins, and defensive enzymes (Alpha- and Beta-esterase). Subsequently, the efficacy of PGR applications was evaluated through phenotypic assessment of larval mine density. Data were subjected to analysis of variance appropriate for a split-split-plot design to quantify the interactions between biochemical profiles and resistance outcomes. All PGR treatments significantly reduced larval mine density compared to the control. Cytokinins (benzyladenine and kinetin) demonstrated superior efficacy, particularly by the third week. Among the cultivars, Castle Rock exhibited the highest constitutive resistance, supported by significantly higher initial levels of total nitrogen, proteins, and defensive enzymes. Principal Component Analysis effectively separated Castle Rock from susceptible cultivars, confirming that constitutive esterase activity and nutrient status are the primary discriminants of resistance. These 2016 screenhouse data establish a physiological proof-of-concept, demonstrating that constitutive biochemical machinery modulates plant resistance via synergistic "bottom-up" effects. While these findings highlight a sustainable pathway for non-chemical pest management, they underscore the need for future multi-season field trials to validate these biochemical insights against current 2026 climate dynamics and evolving pest biotypes, aligning with modern Integrated Pest Management standards.