Biosynthesis of Selenium Nanoparticles from Rosa rugosa Extract: Mechanisms and Applications for Sustainable Crop Protection

Selenium nanoparticles (SeNPs) show great potential for sustainable agriculture, but their green synthesis and practical application still need further optimization. This study established a green synthesis method for SeNPs using lyophilized rose (Rosa rugosa Thunb.) powder as both a reducing and stabilizing agent to reduce sodium selenite (Na2SeO3), key parameters, including template concentration, Na2SeO3/VC ratio, and reaction temperature were systematically optimized. This process yielded stable, spherical SeNPs with optimal properties, exhibiting a diameter of 90 nm and a zeta potential of −35 mV. Structural characterization confirmed that selenium forms chelation complexes through carboxyl and hydroxyl oxygen-binding sites. The SeNPs exhibited exceptional stability (retained 426 days at 25 °C) and pH tolerance (pH 4–10), though divalent cations (Ca2+) triggered aggregation. In agricultural application tests, 5 mg/L SeNPs increased tomato plant biomass by 84% and antioxidant capacity by 152% compared to controls, and the biosynthesis pathways of salicylic acid and jasmonic acid were upregulated. Moreover, the SeNPs exhibited strong concentration-dependent antifungal activity against several major pathogens. Among these pathogens, tomato gray mold (Botrytis cinerea) was the most sensitive, as evidenced by its low EC50 (4.86 mg/L) and sustained high inhibition rates, which remained substantial even at 1 mg/L and reached 94% at 10 mg/L. These findings highlight SeNPs as a friendly alternative for minimizing agrochemical use in sustainable agriculture.