Investigation of Antifungal Activity of Green-Synthesized Silver Nanoparticles on Phytopathogenic Fungi

Silver nanoparticles (SNPs) are nanoparticles of silver that are in the range of 1.0 and 100nm in size. They have unique antimicrobial properties which help in water sanitation and medical industries, but their potentials in agriculture have not been utilized. This study was conducted to investigate the effectiveness of SNPs synthesized using different concentrations of bitter leaf (Vernonia amygdalina) extracts in inhibiting the growth of three plant pathogenic fungi; Fusarium oxysporum, F. solani and Cercospora canescens isolated from diseased plants and identified using molecular method. Synthesized SNPs were characterized using UV-Vis absorption spectroscopy. The antifungal activity of SNPs synthesized at 0, 2, 5 and 10 mins using 0.10g/ml and 0.20g/ml of bitter leaf extracts were evaluated on the basis of colony formation by in-vitro assays. UV-visible spectroscopic analyses revealed rapid reduction of silver ions (Ag+) by bitter leaf extracts where surface Plasmon absorption maxima were observed from the UV-vis spectra. The growth of pathogenic fungi on agar plates were significantly decreased or totally inhibited by treatment with the SNPs depending on the concentrations of the plant extracts and the time of reaction. SNPs synthesized with 0.20g/ml of the extract for 10 mins completely inhibited the growth of the tested fungal pathogens while other SNPs significantly reduced their growth (60 – 90% reduction). The results of this study indicated that the silver nanoparticles synthesized using bitter leaf extracts have potentials to be used as control agents against fungal plant diseases to replace the use of chemical fungicides.