Fungal biosynthesis of silver nanoparticles and their role in control of Fusarium wilt of sweet pepper and soil-borne fungi in vitro

Abstract

Background and Objective: Use of silver nanoparticles (AgNPs) against phytopathogens is a rapidly growing area due to their unique physico-chemical properties. Therefore, the present investigation reports the biosynthesis of AgNPs by Trichoderma harzianum (T. harzianum), a safe fungus for human and plant. Materials and Methods: The synthesized AgNPs were subjected to physical characterization using UV-Visible spectra, fourier transform infrared spectroscopy (FT-IR) and scaninig electron microscopy (SEM) images. Antifungal activity of synthesized AgNPs with poisoned food technique was used against phytopathogenic fungi. Results: UV-Vis spectra with characteristic absorption peak at 415 nm. Biomolecules mediating the synthesis and stabilizing the nanobactericides was confirmed with fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) investigations confirmed that AgNPs were formed with 7.8 nm. Isolation trials from sweet pepper plants showing characteristic symptoms of wilt yielded one fungal isolate which purified and identified as Fusarium oxysporum (F. oxysporum). While two fungal species Alternaria alternata and Trichoderma harzianum were isolated from health plant (no symptoms of wilt). As the applied concentrations of the AgNPs increased, fungal colony formation decreased. AgNPS at concentrations of 20, 40 and 80 ppm inhibited the F. oxysporum growth by 12.5,12.5 and 61.11%, respectively. Concentrations at 80 ppm caused 100% growth inhibition of T. harzianum and A. alternata while concentrations at 100 ppm caused 100% growth inhibition of F. oxysporum. Conclusion: The present study demonstrated that it is possible to perform the biogenic synthesis of AgNPs that used as fungicide against pathogenic fungi.