Phytofabrication of Silver Nanoparticles and Their Potent Antifungal Activity against Phytopathogenic Fungi

Abstract

Fungal plant pathogens cause huge losses in agricultural production by decreasing crop yield and quality. To reduce crop loss from fungal damage, various synthetic fungicides are applied indiscriminately in agricultural practice. The majority of synthetic fungicides are non-biodegradable, and several critical human health risks are associated with them. Green synthesis nanotechnology offers an effectual, cost-effective, ecofriendly, and innocuous method for the synthesis of green nanofungicides, an excellent replacement for synthetic chemical fungicides. Origanum majorana is an aromatic herb with immense pharmacological and medicinal properties. In this context, the present study used the leaves of O. majorana to synthesize silver nanoparticles. The biosynthesized particles showed an absorption peak at 441 nm with ultraviolet-visible spectrophotometry (UV-Vis). The spectra obtained from Fourier transform infrared spectroscopy (FT-IR) of O. majorana extract and AgNPs showed a myriad of functional groups corresponding to vital biomolecules that act as capping and reducing agents. The synthesized silver nanoparticles were spheroidal, and their size measured between 8 nm and 42 nm, as depicted by transmission electron microscopy (TEM). The energy-dispersive X-ray spectrum (EDX) showed a silver peak at 3 keV. The phytofabricated silver NPs demonstrated robust inhibitory activity on the mycelial growth of A. alternata f sp. lycopersici (87%), followed by Pestalotiopsis mangiferae (85%), Macrophomina phaseolina (78%), and Colletotrichum musae (75%). The minimum inhibitory concentration value for A. alternata. f sp. lycopersici and Pestalotiopsis mangiferae was 2 μg/mL, while the minimum fungicidal concentrations were 4 and 8 μg/mL, respectively. Additionally, the fabricated AgNPs induced severe damaging and destructive effects to the morphology of hyphae and conidia, as witnessed by scanning electron microscopy studies.