Biogenic silver-selenium nanocomposites as an effective and sustainable alternative for controlling citrus canker

Abstract

Citrus canker, caused by Xanthomonas citri subsp. citri, remains a major challenge to citrus production and highlights the need for alternatives to conventional bactericides. In this study, silver–selenium nanocomposites (Ag–Se NCs) were synthesized using garlic (Allium sativum L.) extract and characterized by Ultraviolet–visible spectrophotometry (UV–Vis) (plasmon peak ∼400 nm), Scanning Electron Microscopy (SEM) (mean particle size ∼73.7 nm), and Energy-Dispersive X-ray spectroscopy (EDX)/Fourier-Transform Infrared spectroscopy (FTIR) confirming elemental composition and phytochemical capping. Greenhouse evaluations using seven treatments (n = 20 plants each) showed that Ag–Se NCs reduced citrus canker severity significantly. At 200 mg L⁻¹, Ag–Se NCs lowered the infection index from 19% in the pathogen control to ∼1% and decreased the area under the disease progress curve by more than 90%. Treated plants exhibited improved physiological performance, including ∼80% higher total chlorophyll and a ∼30% increase in membrane stability compared with infected controls. Biochemical assessments indicated increases in proline, phenolics, and flavonoids (90–185%), and fruit-quality traits including juice content and ascorbic acid were restored to near-healthy levels. These results demonstrate that garlic-mediated Ag–Se NCs can mitigate disease symptoms and support physiological and fruit-quality recovery under greenhouse conditions. Further studies incorporating mechanistic analyses, broader dose responses, and field validation are recommended to confirm their suitability for integrated citrus canker management.