Antifungal and Anti-Oomycete Potential of Ag2S-S Janus and Ag Nanoparticles Synthesized with Non-Toxic Agents and Their Application to Control Fusarium Wilt of Tomato

The excessive use of fungicides in agriculture has generated environmental problems, increased resistance in plant pathogenic fungi, and raised concerns for food safety and human health. This study evaluates silver-based nanoparticles (NPs) as a potential alternative for the control of plant pathogens. Ag2S-S Janus and AgNPs were synthesized through chemical reduction using non-toxic compounds, employing glucose as a reducing agent (0.30 and 0.90%) and gelatin as a passivating agent (0.50 and 1.00%), generating four treatments. The synthesized NPs showed average sizes ranging from 5 to 11 nm, with the smallest particles obtained in treatment T3 (5.90 ± 0.30 nm) and the largest in T4 (10.34 ± 0.46 nm). The antifungal and anti-oomycete activity of the NPs was evaluated in vitro against four microorganisms: Alternaria alternata, Colletotrichum boninense, Fusarium oxysporum, and Phytophthora capsici. Results showed complete inhibition (100%) of A. alternata and 60–70% inhibition of P. capsici in all treatments, demonstrating strong antimicrobial potential. Additionally, NPs were applied to tomato seedlings (Solanum lycopersicum) inoculated with Fusarium oxysporum f. sp. lycopersici. NPs were not phytotoxic and reduced disease severity (on a 1–2 scale) while promoting lesion healing.