Biosynthesis of Silver Nanoparticles from Streptomyces Spp., Characterization and Evaluating of Its Efficacy against Phomopsis theae and Poria hypolateria in Tea Plants (Camellia sinensis)

The biosynthesis of metal nanoparticles is an emerging area of advanced research in plant protection. In this study, an eco-friendly and rapid protocol was developed where silver nanoparticles were biosynthesized by using Streptomyces spp. The biocontrol agent was isolated from different tea soils and the efficient strain (VASC201) was identified by dual culture and antibiosis. Nanoparticles were successfully synthesized from this efficient strain. The silver nanoparticles exhibited their resonance peak at 448 nm under ultraviolet-visible spectroscopy (UV-Vis). The structural analysis  of the silver nanoparticles synthesized by the Streptomyces spp. exhibited a strong crystalline structure. The morphology and chemical composition of the silver nanoparticle were examined by high-resolution transmission electron microscopy (HR-TEM) equipped with energy-dispersive X-ray spectrometer (EDX) and were predominantly spherical in shape and uniformly distributed without significant agglomeration. The average crystalline size of the prepared silver nanoparticle was found to be 51.2 nm. The stretching vibrational peak at 3420, 2920 and 2350 cm^-1 in Fourier-transform infrared spectroscopy (FTIR) were attributed to various functional group of metal nanoparticle synthesis. We assessed the effectiveness of silver nanoparticles against Poria hypolateritia and Phomopsis theae. The results showed that the nanoparticles showed very good inhibitory effect of about 69.90% inhibition of Poria at 5 ppm concentration on the 15th day. Phomopsis was inhibited to 67.47% at 5 ppm of silver nanoparticles at the same time interval