Nanomaterials for the control of the onion phytopathogen Botrytis squamosa

Abstract

Nanomaterials can modulate plant physiology and plant–microbe interactions, offering sustainable alternatives for disease control. This study describes the synthesis and characterization of silver nanoparticles (from Phanerochaete chrysosporium), chitosan nanoparticles, and chitosan–silver nanohybrids, and evaluates their effects on the Botrytis squamosa–Allium cepa pathosystem. Silver nanoparticles were synthesized by fungal-mediated bioreduction, chitosan nanoparticles by ionic gelation, and nanohybrids by combining chitosan and silver nanoparticles. Nanomaterials were characterized by UV–visible spectroscopy, dynamic light scattering, ζ-potential, Xray diffraction, ATR-FTIR spectroscopy, and TEM. In vitro antifungal assays, determining the effective nanomaterial concentration for 50 % inhibition of mycelial growth, demonstrated strong inhibition of B. squamosa, with chitosan–silver nanohybrids showing the highest activity. Controlled environment trials using Allium cepa (onion) whole pot plants demonstrated that chitosan nanoparticles and chitosan–silver nanohybrids reduced disease severity and induced the activity of enzymes involved in resistance mechanisms. Notably, this is the first report on the use of both chitosan-based nanomaterials in the B. squamosa–A. cepa pathosystem, revealing their potential to both suppress the pathogen and stimulate plant immunity. Treated plants showed increased activity of defense-related enzymes, suggesting nanoparticle-mediated priming of defense responses. These findings suggest a dual mechanism of action: direct antifungal effects and activation of plant defense responses. This work advances our understanding of nanoparticle–plant–pathogen interactions and underscores the value of biogenic nanomaterials as environmentally friendly tools for crop protection. By elucidating the biochemical responses elicited by nanomaterials, the study contributes novel insights into the molecular basis of enhanced plant resilience.