Comparative evaluation of silica and silver nanoparticles for alleviating biotic stress caused by Fusarium graminearum in wheat through modulation of physiological and antioxidant defense mechanisms

Fungal pathogens pose a serious threat to wheat productivity by impairing plant water relations, membrane integrity, and metabolic functions. Recent advances in nanotechnology have highlighted the potential of nanoparticles as priming agents to enhance plant tolerance against biotic stresses. Therefore, this study evaluated the efficacy of silver nanoparticles (AgNPs) and silica nanoparticles (SiNPs) in modulating physiological and biochemical responses of wheat under fungal stress. Fungal infection significantly reduced relative water content (RWC), membrane stability index (MSI), protein content, osmotic potential, and photosynthetic pigments, while increasing soluble sugars, proline accumulation, and antioxidant enzyme activities. However, nanoparticle priming markedly alleviated these adverse effects in a concentration-dependent manner. AgNPs at 50-75 mg L⁻¹ and SiNPs at 50-100 mg L⁻¹ significantly improved RWC and MSI under stress. Protein content was maximized at 75 mg L⁻¹ AgNPs and 100 mg L⁻¹ SiNPs. Both nanoparticles further enhanced soluble sugar accumulation and reduced osmotic potential, indicating improved osmotic adjustment. Chlorophyll and carotenoid contents were notably enhanced, particularly with 75 mg L⁻¹ AgNPs and 100 mg L⁻¹ SiNPs. Although proline levels increased under stress, nanoparticle treatments generally reduced its accumulation compared to untreated stressed plants. Furthermore, higher concentrations of both nanoparticles significantly stimulated antioxidant enzyme activities (SOD, POD, and CAT), strengthening the plant defense system. In conclusion, AgNPs and SiNPs alleviate fungal stress in wheat by enhancing physiological stability and biochemical defenses, with 75 mg L⁻¹ AgNPs and 100 mg L⁻¹ SiNPs identified as optimal concentrations for improving stress tolerance and supporting sustainable crop protection.