Synthesis, characterization, and antifungal activity of chitosan-copper nanocomposites against crop pathogens

Chitosan-copper nanoparticles (CHT-Cu NPs) were synthesized using an ionic gelation approach and evaluated for their physicochemical properties and antifungal activity against major fungal pathogens of chickpea and citrus. For instance, "In recent years, nanotechnology-based formulations have emerged as promising strategy for sustainable disease management". Dynamic light scattering analysis revealed uniformly sized nanoparticles (~150 nm) with low polydispersity and a positive surface charge (+22.2 mV). Fourier transform infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray analysis confirmed effective copper coordination, amorphous nanocomposite formation, and stable incorporation of copper within the chitosan matrix. The antifungal efficacy of CHT-Cu NPs was assessed in vitro against Colletotrichum ciceri, Fusarium ciceri, Rhizoctonia bataticola, Sclerotium rolfsii, and Colletotrichum gloeosporioides. The nanocomposites exhibited strong, concentration-dependent inhibition of mycelial growth. F. ciceri was highly sensitive, showing complete inhibition at all tested concentrations (≥100 µg mL^-¹). S. rolfsii and chickpea pathogens C. ciceri and R. bataticola were completely inhibited at concentrations 200 µg mL^-¹, 300 µg mL^-¹ and 300 µg mL^-¹, respectively, whereas C. gloeosporioides was comparatively less sensitive and required higher concentrations (≥400 µg mL^-¹) for complete suppression. In contrast, chitosan alone and copper sulfate showed only moderate antifungal activity. These findings demonstrate that CHT-Cu NPs possess broad-spectrum antifungal activity and superior efficacy compared to conventional fungicides, highlighting their potential as eco-compatible nanobiopesticides for sustainable management of fungal diseases in crop plants.