Extracellular biosynthesis of silver nanoparticles using Streptomyces griseoplanus SAI-25 and its antifungal activity against Macrophomina phaseolina, the charcoal rot pathogen of sorghum

Streptomyces griseoplanus SAI-25 isolated from rice rhizospheric soils with previously demonstrated insecticidal activity is currently characterized for silver nanoparticle synthesis using its extracellular extract. The synthesized particles showed the characteristic absorption spectra of silver nanoparticles at 413-417 nm. Spectral analysis by FTIR confirmed the presence of alcohols, amines, phenols and protein in the cell-free extracellular extract of SAI-25. These functional groups could have served dual roles in silver nanoparticle synthesis like reducing and stabilizing agents. Microscopic and spectroscopic analysis such as SEM, TEM, EDAX and XRD has provided the size, shape and composition of the synthesized nanoparticles. DLS and Zeta potential further confirms the size and characteristic negative charges of AgNPs respectively. The observed antifungal activity against charcoal rot pathogen Macrophomina phaseolina shows a base for the development of Streptomyces mediated nanoparticles in controlling this polyphagus pathogen and key role of biopesticides in improving agricultural economy.