Isolation and identification of toxigenic fungi from infected peanuts and efficacy of silver nanoparticles against them

Abstract

Peanuts are vulnerable to fungal infections during long term storage. Fungi infecting peanuts are toxigenic and cause health hazards. The goal of this study was isolation and identification of fungi in peanuts and use of silver nanoparticles (AgNPs) to inhibit them. For this purpose firstly, we have isolated fungi from infected peanuts and identified on the basis of morphological and molecular study. Out of the total 54 fungal isolates, 47 were found to be Aspergillus spp. and other belongs to Penicillium spp. and Macrophomina phaseolina. Biochemical assay was performed to identify cultures of Aspergillus flavus from other species of this genus by inoculating it on Aspergillus Differentiation Medium (ADM). Thirty-one isolates were found to be A. flavus. Toxicity of Aspergillus spp. was evaluated on Yeast Extract Sucrose agar (YES) medium with an additive methylated β-cyclodextrin and nine isolates were found toxigenic. Secondly, AgNPs were synthesized from ten different plants and their characterization was performed using various analytical techniques such as UV–Visible spectrophotometer, Fourier Transform Infrared Spectroscopy, Zetasizer and Nanoparticle Tracking Analysis, etc. Further, antifungal potential of thus synthesized AgNPs was evaluated. All the synthesized AgNPs possess ability to inhibit fungal growth. Cymbopogon citratus leaf extract mediated AgNPs were found to have prominent antifungal potential against all test fungi and its minimum inhibitory concentration (MIC) was found to be 20 μg/ml. The biogenic approach proposed in the present study is eco-friendly, safe and economical viable. AgNPs also reported to have significant antifungal activity against toxigenic isolates of peanuts, hence such AgNPs can be effectively used for the management of toxigenic pathogens.