Effective Inhibition of Phytopathogenic Microbes by Eco-Friendly Leaf Extract Mediated Silver Nanoparticles (AgNPs)

This study was aimed at producing the eco-friendly, safe, and inexpensive silver (Ag) nanoparticles (NPs) and assessing its antimicrobial activity. Fungal pathogens isolated from diseased leaves and fruits of brinjal and bacterial pathogen obtained from a culture collection were used in this study. Green synthesis of AgNPs was performed and optimized using Azadirachta indica leaf extract. The newly synthesized AgNPs (lambda(max)=437nm) showed isotropism in size (crystal size/diameter: 21/295nm) and morphology under transmission and scanning electron microscopy and energy dispersive X-ray analysis. The fourier transform infrared spectroscopy data suggested the role of various aliphatic/aromatic moieties and proteins in AgNPs stabilization. The AgNPs reduced the growth of Penicillium sp. maximally by 92% after 6days. The sensitivity of test fungi towards AgNPs followed the order: Penicillium sp. (92%)>Fusarium sp. (89%)>Aspergillus sp. (69%). Exposure of Ralstonia solanacearum to AgNPs (MIC/MBC 200/400 mu gml(-1)) displayed damaged cellular envelopes, bulging of cells, and pit formation. The nucleic acid discharge showed a progressive increase from 8 to 34% (r(2)=0.97). The cellular metabolic activity and surface adhering ability of R. solanacearum were completely lost at 400 mu gAgNPs ml(-1). Results suggested that the AgNPs synthesized in this study had enough anti-pathogenic potential and could inexpensively and safely be used as a promising alternative to agrochemicals. Moreover, the findings observed in this study is likely to serve as an important indicator for the development of effective nano-control agents which in effect would help to manage some deadly phyto-pathogens capable of causing heavy losses to agricultural production systems. [GRAPHICS] .