Synthesis and antibacterial activity of solanum torvum mediated silver nanoparticle against Xanthomonas axonopodis pv. punicae and Ralstonia solanacearum.

To meet the food demand of growing population, agricultural productivity needs to be increased by employing safe strategies without harming ecosystem. Silver nanoparticle (AgNP) using a green approach has become a promising substitute to the synthetic pesticides to overcome pest menace. In this study, AgNPs were synthesized from Solanum torvum fruit extract and their bactericidal property against phyto bacteria was shown. UV-visible spectroscopic observation revealed a surface resonance peak of 440 nm corresponding to the formation of AgNPs. Microscopic and particle-size analyses showed a nearly spherical size, with an average diameter of 27 nm. Surface charge and polydispersity index of the synthesized AgNPs were -11.8 mV and 0.29, respectively. Powder X-ray diffraction, energy-dispersive X-ray and Infrared spectroscopy techniques were used to explore phase formation, composition and possible biological molecules involved in AgNP formation. AgNPs exhibited minimum inhibitory concentrations of 6.25 µg mL^-1 and 12.5 µg mL^-1 against bacterial plant pathogens Xanthomonas axonopodis pv. punicae and Ralstonia solanacearum. In-vitro disk-diffusion assay showed inhibition zones of 11.4 ± 1 mm for R. solanacearum and 18.1 ± 1 mm for X. axonopodis pv. punicae treated with 50 µg mL^-1 AgNPs. The AgNPs generated intracellular reactive oxygen species in the pathogens. DNA damage and DNA replication inhibition studies showed genotoxicity of AgNPs to the bacterial cells. A plant toxicity study demonstrated a nontoxic effect of the synthesized NPs. Overall; the results show that AgNPs can be used as an economically feasible, ecologically safe and effective approach to overcome bacterial diseases.