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Abstract
Background: The rising concern over chemical fungicide residues in food crops has pushed researchers to look for safer, greener alternatives. Silver nanoparticles (AgNPs) prepared through plant-based routes have gained particular attention owing to their documented antimicrobial properties and relatively low production costs. Tomato (Solanum lycopersicum) is among the most widely grown vegetable crops worldwide, yet its productivity in Pakistan remains constrained by soil-borne diseases, most notably Fusarium wilt. In this study, we synthesized AgNPs using a methanolic extract of Micromeria biflora (Lamiaceae) and evaluated their effects on early tomato growth and Fusarium wilt incidence under pot conditions.
Methods: The methanolic extract of shade-dried M. biflora aerial parts was reacted with silver nitrate solution at room temperature. Formation of AgNPs was confirmed through a visible colour shift and subsequently verified by UV-Vis spectroscopy, which showed a surface plasmon resonance peak at approximately 432 nm. A pot experiment involving five treatments — distilled water (negative control), crude M. biflora extract, AgNPs at 20 ppm, AgNPs at 40 ppm, and triadimefon (chemical fungicide, positive control) — was established with three replicates per treatment. Nine morphological parameters along with biomass and disease endpoints were recorded one week after treatment application.
Results: A clear dose-dependent response was observed. Plants receiving 20 ppm AgNPs exhibited the strongest overall growth, outperforming all other treatments across eight of nine morphological outcomes. Flower number increased by 82.5%, stem width by 31.2%, and leaf length by 22.5% over the water control. Fresh biomass at 20 ppm reached 91.0 ± 3.0 g compared to 68.0 ± 2.0 g in the control. Fusarium wilt disease severity was reduced to 14.0 ± 3.0% at 20 ppm versus 72.0 ± 4.0% in untreated plants, a reduction comparable to triadimefon (18.0 ± 3.0%). In contrast, the 40 ppm treatment showed inhibitory effects on six of nine growth parameters, suggesting phytotoxicity at higher concentrations.
Conclusions: Green-synthesized AgNPs from M. biflora enhanced tomato growth and suppressed Fusarium wilt in a concentration-dependent fashion, with 20 ppm emerging as the optimal dose. These results position biosynthesized AgNPs as a promising, eco-friendly tool for integrated disease management in tomato cultivation, though field-scale validation remains necessary.