Antifungal potential of silver and copper nanoparticles in suppressing Tilletia indica for Karnal bunt resistance in wheat

Karnal bunt disease, caused by the fungus Tilletia indica, poses a real threat to wheat grains and trade, emphasizing the need for effective management. We investigated the antifungal activity of silver (Ag) and copper (Cu) nanoparticles (NPs) against T. indica. The NPs were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV-vis spectroscopy, which confirmed uniformity in size distribution and well dispersion. TEM analysis presented spherical particles around 5–15 nm in size, while DLS measurements displayed average diameters of 12.1 nm for Ag-NPs and 8.7 nm for Cu-NPs. UV-vis spectroscopy examination confirmed the formation of nanoparticles, with plasmon bands at 440 nm for Ag and 405 nm for Cu. Both Ag and Cu-NPs exhibited dose-dependent inhibition effects, with Ag-NPs showing a higher inhibition rate than the others at all concentrations. In the minimum inhibitory concentration assessment, Ag- and Cu-treated samples at 400 µg/mL exhibited a highly significant suppression of mycelial growth compared to the control. The inhibition of radial growth (IRG%) assay showed a significant reduction in colony size at 100 µg/mL, with Ag and Cu-NPs inhibiting growth of 75% and 65%, respectively. We further analyzed spore germination assays, which showed that Ag-NPs achieved the most substantial inhibition at 200 µg/mL, with suppressing germination over 80% compared to a 70% reduction by Cu-NPs. Furthermore, nanoparticles significantly increased the expression of defense-related genes, with Ag-NPs causing a much stronger response compared with Cu-NPs. Specifically, PR1 and PR6 showed the most considerable fold change observed at 96 h, indicative of improved plant defense. Thus, these findings demonstrate that Ag and Cu-NPs are potent antifungal agents, with Ag-NPs emerging as a promising and effective strategy for controlling T. indica infections and inducing plant resistance in wheat plants.