Green Synthesis and Characterization of Silver Nanoparticles and Their Effects on Disease Incidence Against Canker and Biochemical Profile in Citrus reticulata L.

Green synthesis of nanoparticles is an emerging class of nanotechnology. In the last few years, secondary metabolites have been extensively explored for nanoparticle synthesis because they are eco-friendly, energy efficient, less hazardous, and more stable compared to their chemically synthesized counterparts. In the present study, silver nanoparticles (AgNPs) were synthesized by utilizing Moringa oleifera leaves as the main reducing and stabilizing agent. The synthesized AgNPs were characterized through UV-visible spectroscopy, zeta analyzer, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction spectroscopy (XRD). UV-visible spectroscopy confirmed the surface plasmon resonance (SPR) band in the range of 423 nm to 425 nm, while the zeta analyzer clarified that the synthesized AgNPs ranged from 8 nm to 28 nm in size. SEM showed the rectangular segments fused together, and XRD confirmed the crystalline nature of the synthesized AgNPs. The presence of metallic silver ions was confirmed by an EDX detector. Different concentrations (10, 20, 30, and 40 ppm) of the green synthesized AgNPs were exogenously applied on Citrus reticulata before applying an inoculum of Xanthomonas axonopodis pv. citri to record the disease incidence against canker disease at different day intervals. The infection index values were progressively increased in all the applied treatments with the passage of time. AgNPs at a concentration of 30 ppm were found to be more suitable for creating a resistance against canker disease. Moreover, the effects of green synthesized AgNPs were also assessed for biochemical profiling in C. reticulata. The AgNPs treatment before the applications of Xanthomonas axonopodis pv. citri reduced stress in plants. The application of AgNPs reduced the production of antioxidant activity, antioxidative enzymes, and non-enzymatic compounds but enhanced production of total protein content. The present work highlights the potent role of green synthesized AgNPs, which can be as used as a biological control of citrus disease.