Journal of Advances in Biology & Biotechnology

Late blight, caused by the oomycete Phytophthora infestans, remains one of the most devastating diseases affecting tomato cultivation globally. As concerns over chemical residues and pathogen resistance grow, eco-friendly management strategies utilizing green-synthesized nanoparticles and botanical extracts have gained prominence as viable alternatives to conventional fungicides.The present investigation, conducted during the 2023–24 season, evaluated the efficacy of silver nanoparticles (AgNPs), copper nanoparticles (CuNPs), neem extracts, and mancozeb in modulating biochemical defense parameters in tomato foliage. The treatments were assessed for their ability to induce systemic resistance by quantifying changes in total soluble protein, total phenol content, salicylic acid levels, and peroxidase (PO) activity at 2, 5, 8, and 11 days after inoculation (DAI). The experimental results revealed that all treatments significantly bolstered the host's biochemical defenses compared to the infected control. Notably, Treatment T₃ (AgNPs @ 100 ppm) emerged as the most potent elicitor, achieving peak enhancements at 8 DAI. Under this treatment, total soluble protein, phenol content, salicylic acid levels and peroxidase activity were increased by 93.37, 82.61, 87.13 and 94.96 per cent, respectively relative to the infected control.These findings strongly suggest that green-synthesized silver nanoparticles effectively prime the plant's immune system, triggering a robust defense response that limits the progression of P. infestans. Consequently, the application of AgNPs represents a highly effective and sustainable tool for the integrated management of late blight in tomato crops.