Biogenic synthesis of selenium nanoparticles by Bacillus amyloliquefaciens: A promising method for mitigating mycotoxin contamination and fighting Fusarium graminearum.

Selenium is an essential micronutrient, but in its toxic selenite (SeO₃²⁻) form, it poses significant environmental and health risks. Elevated levels of selenite can adversely affect ecosystems and agricultural productivity. This study investigates the potential of the endophytic bacterium Bacillus amyloliquefaciens, isolated from wheat roots, to mitigate selenium toxicity by converting selenite into environmentally safe selenium nanoparticles (SeNPs). SeNPs were synthesized and characterized using various spectroscopic and electron microscopy techniques. These SeNPs exhibited a smooth, spherical shape with diameters ranging from 22 to 89 nm. Their antifungal properties were evaluated in vitro against Fusarium graminearum, a pathogen responsible for Fusarium head blight in wheat. Results demonstrated that SeNPs at concentrations of 5, 10, and 20 μg/mL inhibited the growth of F. graminearum by 70.35 %, 100 %, and 100 %, respectively. SeNPs also significantly enhanced the activity of key antioxidant enzymes-peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD)-in wheat plants, reducing F. graminearum colonization and disease incidence. In addition, SeNPs suppressed the accumulation of the mycotoxin deoxynivalenol (DON), with levels reducing from 31.40 μg/g to 3.42 μg/g in GYEP medium and from 8.89 mg/kg to 1.50 mg/kg in wheat ears, by downregulating the FgTRI genes involved in its biosynthesis. Furthermore, SeNPs improved seedling growth under infection stress, enhanced seed germination, and promoted plant growth, including increased plant height, fresh and dry weight, and chlorophyll content. These findings highlight the potential of SeNPs, generated by selenite-resistant bacteria, as a sustainable, natural approach to combat Fusarium head blight and mitigate mycotoxin contamination. Compared to traditional chemical control methods, this approach offers advantages such as low toxicity, environmental sustainability, biodegradability, and cost-effectiveness. Future studies should focus on the large-scale application of SeNPs in field conditions to further validate their safety effectiveness in real-world agricultural settings.