Seasonal and Genotypic Variability in Wheat Antioxidant Response to Fusarium Infection Under Different Nitrogen Treatments

Wheat production worldwide is significantly threatened by phytopathogenic fungi of the genus Fusarium, while inadequate nitrogen fertilization can contribute to the development of Fusarium head blight (FHB), ultimately leading to reduced yield and grain quality. This study aimed to elucidate the individual and interactive effects of genotype, Fusarium inoculation and different nitrogen treatments on the antioxidant response of wheat spikes across two growing seasons. The study was conducted under field conditions on four winter wheat genotypes differing in FHB susceptibility. Oxidative stress was assessed by lipid peroxidation, and antioxidant responses by glutathione content and antioxidant enzyme activities. The results showed that wheat antioxidant responses to Fusarium infection were mainly shaped by genotype and seasonal conditions, with significant genotype-dependent interactions with nitrogen supply. FHB-susceptible genotypes, Srpanjka and Sofru, showed consistently lower basal glutathione levels and glutathione S-transferase activity than the resistant genotypes Apache and Graindor in both growing seasons. In both seasons, Fusarium inoculation increased guaiacol peroxidase activity in most genotypes, suggesting a consistent association with infection response. These findings improve understanding of wheat defence responses under varying nitrogen levels and may support more effective FHB management. Overall, the results indicate that antioxidant responses reflect both defence activation and stress intensity, depending on genotype and environmental conditions.