Biopesticidal Efficacy of Green Synthesized Selenium-Doped Zinc Oxide Nanoparticles against Macrophomina phaseolina The causal agent of Maize Charcoal Rot

This study explores the potential antagonistic effects of selenium-doped zinc oxide nanoparticles (Se-ZnO NPs), synthesized through a sustainable approach, on maize charcoal rot induced by the fungus Macrophomina phaseolina. Se-ZnO-NPs were prepared using the rhizobium extract of Curcuma longa and characterized for their physicochemical properties. Characterization included various in vitro parameters such as FTIR, ICP-MS, particle size, PDI, and zeta potential. ICP-MS analysis revealed Se and Zn ion concentrations of 54.43 mg L^-1 and 71.70 mg L^-1, respectively. SEM analysis indicated a size of 37 nm with polyhedral morphology for the Se-ZnO-NPs. Additionally, EDX spectra confirmed the presence of Se and Zn in the nanoparticles. In vitro assays demonstrated that the highest nanoparticle concentration significantly inhibited M. phaseolina growth and spore germination, accompanied by increased enzyme activities. Greenhouse experiments were conducted to assess the efficacy of Se-ZnO-NPs in reducing charcoal rot severity in maize plants under controlled conditions. Furthermore, a second study evaluated various growth parameters of maize plants, such as shoot and root length, and biomass after 45 days of germination. Physiological attributes such as total chlorophyll content and reducing sugar were examined, while biochemical traits including total protein content, catalase, and polyphenol oxidase were assessed after the same germination period. The results indicated that soil amended with various concentrations (0.8 to 12.5 μg/ml) of NPs significantly enhanced maize plant growth compared to the respective positive control. The antifungal activity of the Se-ZnO-NPs against M. phaseolina showed a significant reduction in growth. Thus, the findings suggest that green-synthesized Se-ZnO-NPs could effectively combat the charcoal rot pathogen. However, further field experiments are needed to explore the activity of doped nanoparticles in soil against pathogens.