Insights into tomato growth stimulation and induced resistance against Fusarium oxysporum f. sp. lycopersici by magnetite nanoparticles

Agricultural productivity faces increasing challenges from fungal diseases and nutrient deficiencies, necessitating innovative solutions. While iron oxide nanoparticles show promise in agriculture, their effects on hormone-mediated growth regulation and disease resistance remain poorly understood. This study investigated the effects of Fe₃O₄ NPs on tomato growth and resistance against Fusarium oxysporum f. sp. lycopersici Fol. Tomato seedlings were hydroponically grown and treated with 0.5 and 1.0 mg/L Fe₃O₄ NPs or equivalent FeCl₃ concentrations. Treatment with 0.5 mg/L Fe₃O₄ NPs enhanced root length by 100 % and shoot length by 40 % compared to controls, outperforming FeCl₃ treatments which increased root and shoot length by only 36.7 % and 8.5 %, respectively. Fe₃O₄ NPs downregulated ABA-related genes, with FMO, MYB71, and DnaJ1 expression decreasing by 71 %, 46 %, and 55 % respectively after 24 hours. Seedlings treated with 0.5 mg/L Fe₃O₄ NPs before Fol inoculation showed a 62.9 % reduction in disease severity as measured by AUDPC value of 1.3 versus 3.7 in controls and a 5-fold increase in ROS accumulation at 48 hours post-infection. Fe₃O₄ NPs strongly induced defense-related genes, with PR1a, LoxC, and AOC showing 14-fold, 182.1 %, and 111.2 % increased expression respectively within 12 hours of treatment. SA levels increased by 56.1 % and 68.6 % at 12- and 24-hours post-treatment. This priming effect was amplified when NP-treated plants were challenged with Fol. These findings demonstrate Fe₃O₄ NPs’ potential as a multifunctional nano-fertilizer, promoting both growth and disease resistance through modulation of phytohormone pathways.