Biogenic nanoparticles for managing Sclerotium rolfsii-induced rots in schefflera plants: Impacts on growth and phytohormone-regulation

Sclerotium rolfsii attacks schefflera plants, causing collar, stem, and root-rot diseases, which drastically reduce schefflera productivity. This study focused on the impact of novel applications of green-synthesized magnesium and zinc oxide nanoparticles, obtained from leaf extracts of Zizyphus Spina - Christi L. (sidr-Zs) and Eucalyptus citriodora (Hook.) (camphor-Ca), on enhancing resistance to S. rolfsii diseases through functional anatomical defense and modulation of phytohormone levels. Green-synthesized MgO and ZnO NPs exhibited spherical to ellipsoid shapes, with ZnONPs sizes from 58.77 nm (sidr) to 91.28 nm (camphor). Meanwhile, MgONPs 34.84 nm and 86.06 nm, crystallinity was confirmed with XRD. The greatest reduction in mycelial dry weight and oxalic acid was achieved with 200 mg/l of MgONP-Zs (94.02 % - 297 mg/l), followed by 200 mg/l of ZnONP-Zs (82.02 % - 384 mg/l). MgONPs-Zs followed by MgONPs-Ca and ZnONPs-Ca nanoparticles demonstrated optimal efficacy in controlling collar, stem, and root-rot in schefflera plants when applied twice as a soil drench at 200 mg/l, resulting in enhanced epidermal intensity, increased endogenous plant hormone levels, and a reduction in disease incidence and severity to 12.5 % and 3.12 %, respectively, which aligns with improved growth characteristics. MgONP treatments reduced ABA, while increasing gibberellic acid (GA), kinetin, and 2,4-dichlorophenoxyacetic acid (2,4-D) in schefflera plants. The integration of nanotechnology in sustainable agriculture is made possible by this study, which supports the potential use of green-synthesized ZnO and MgONPs from plant extracts as an economical and ecologically friendly method of enhancing the plant's resistance to S. rolfsii attack, and enhancing schefflera plant development and elevated phytohormone levels. • Green-synthesized ZnO and MgO nanoparticles effectively manage Sclerotium rot. • Activating specific growth hormones like GA, reducing ABA levels. • Promoting growth, and reducing disease severity in ornamental plants. • Modulation of phytohormone signaling by nanoparticles is a novel strategy for enhancing crop immunity.