Using Cell-Free Filtrate of Nematophagous Trichoderma to Synthesize Silver Nanoparticles and Evaluate Their Efficacy to Control Eggplant Root-Knot Nematode

Root-knot nematodes are economically important plant-parasitic nematodes that damage roots, reduce plant growth, and limit crop productivity. Silver nanoparticles (AgNPs) synthesized through biological processes have attracted interest as potential alternatives to conventional nematicides. Fungi can facilitate nanoparticle synthesis through the action of extracellular or intracellular biomolecules. This study evaluated indigenous nematophagous Trichoderma isolates for the biosynthesis of biogenic AgNPs and investigated their nematicidal activity against Meloidogyne javanica in vitro and under greenhouse conditions. The fungus has good potential for synthesizing BAgNPs from silver nitrate. The color change was observed after 72 h of incubation. Additionally, physicochemical characterization of BAgNPs by UV-visible spectroscopy, dynamic light scattering (DLS), zeta potential, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM) revealed a spherical shape, homogeneity, and particle size ranging from 10–44 nm. Furthermore, three concentrations of BAgNP and control (0.0, 500, 750, 1000 µg/L) were examined against M. javanica egg hatch inhibition and mortality of second-stage juveniles (J2s) in vitro. Results indicated that BAgNPs (at 1000 µg/L) significantly (p ≤ 0.05) suppressed egg hatch by 62.77% and increased J2s mortality percentage (65.67%). Biogenic AgNPs were found to have a positive impact on eggplant seed germination in vitro. Under greenhouse conditions, BAgNPs promoted plant growth and inhibited M. javanica reproduction (1.4–1.7 at 1000 µg/L) and root galling. Thus, BAgNPs synthesized using Trichoderma showed ovicidal and larvicidal activity against M. javanica. In addition, BAgNPs stimulated plant growth in planta, highlighting their potential as candidates for nematode management and as nanobiostimulants. However, further studies are needed to assess silver accumulation, environmental fate, and potential effects on non-target organisms in soil–plant systems. In future work, the role of BAgNPs in managing M. javanica under field trials, gene expression for treating plants, and the mode of action against plant-parasitic nematodes should be studied.