Integrated biosynthesized silver nanoparticles, chitosan, and Trichoderma asperelloides for managing onion white rot under greenhouse conditions.

Onion white rot, caused by Sclerotium cepivorum (Stromatinia cepivora), remains difficult to manage because of the long-term persistence of sclerotia in soil and the limited efficacy of conventional control methods. In this greenhouse study, we evaluated an integrated eco-friendly strategy comprising Trichoderma asperelloides, biologically synthesized silver nanoparticles (AgNPs), and an AgNP-chitosan formulation to suppress onion white rot and improve plant performance. The pathogen and antagonistic isolate were identified morphologically and molecularly, and the synthesized nanomaterials were physicochemically characterized. Among all treatments, the combined AgNP-chitosan + T. asperelloides treatment showed the strongest effect, reducing disease severity by 94.3% relative to the infected control and significantly improving bulb fresh weight, leaf length, and leaf number. This treatment also reduced malondialdehyde and hydrogen peroxide contents and was associated with increased antioxidant enzyme activities. These findings suggest that the integrated treatment may act through a synergistic combination of direct pathogen suppression and improved regulation of oxidative stress in treated plants. Overall, the results support the potential of this nano-biological strategy for managing onion white rot under controlled greenhouse conditions, although field validation is still required.