Reduction of peanut pod rots and aflatoxin contamination using selected micronutrient nanoparticles

Abstract

Climate-induced biological changes have altered host–pathogen interactions, highlighting the urgent need to strengthen plant defense mechanisms using environmentally safe alternatives to conventional fungicides that often pose ecological risks. This study evaluated the efficacy of micronutrient nanoparticles-iron oxide (Fe₃O₄), manganese oxide (MnO), and zinc oxide (ZnO)-at concentrations of 0, 25, 50, and 100 mg L^-¹ in mitigating peanut (Arachis hypogaea L.) pod rot and reducing contamination by aflatoxigenic fungi (Aspergillus flavus and A. parasiticus). Greenhouse and field trials were conducted during the 2022 and 2023 growing seasons to assess their effects on disease incidence, fungal frequency, aflatoxin levels, yield performance, and associated biochemical responses. All nanoparticle treatments significantly reduced pod-rot incidence and aflatoxigenic fungal contamination, with concomitant improvements in yield relative to the untreated control Fe₃O₄ nanoparticles at 100 mg L^-¹ exhibited the most excellent efficacy, achieving marked reductions in disease severity and aflatoxin accumulation, while enhancing the activity of antioxidant enzymes (peroxidase, polyphenol oxidase, and catalase) and increasing phenolic compounds, sugars, free amino acids, and protein content. MnO nanoparticles also showed notable but comparatively lower effects, whereas high concentrations of ZnO nanoparticles were associated with increased fungal infection and aflatoxin levels. The findings highlight the potential of micronutrient nanoparticles, particularly Fe₃O₄, as eco-friendly resistance inducers that enhance both biochemical and physiological defenses in peanut plants under biotic stress, provided their concentrations are carefully optimized.