Biogenic silver nanoparticles as an antibacterial agent against bacterial leaf blight causing rice phytopathogen Xanthomonas oryzae pv. oryzae

Abstract

Silver nanoparticles (Ag NP) were produced utilizing leaf extract of rice cultivar Taichung native-1. Various factors like leaf extract, silver nitrate concentrations, and duration of autoclaving were standardized during synthesis. Nanoparticles were analyzed with UV-visible absorption spectroscopy (UV-vis), dynamic light scattering, zeta potential, X-ray diffraction and transmission electron microscopy techniques. The synthesis was noted at 0.4% extract, 0.6 mM silver nitrate, 30 min of autoclaving and NP formation was confirmed from 424 nm peak in UV-vis. NP showed zeta potential of - 27 mV, face-centered cubic (fcc) crystal nature and sized around 16.5 ± 5.9 nm. Biogenic NP synthesized from susceptible rice variety were used as an antibacterial agent against phytopathogen Xanthomonas oryzae pv. oryzae (Xoo), the causative agent of bacterial leaf blight (BLB) disease in rice. Antibacterial effect of Ag NP was evaluated using in vitro assays and in vivo efficacy under greenhouse conditions. Results confirmed effective inhibition of Xoo growth and colony formation by Ag NP and found to be the more powerful antibacterial agent. Besides, Ag NP treatment (10 µg/mL) caused an enhancement in seedling vigor index. Pots treated with Ag NP (15 μg/mL) in vivo in greenhouse showed disease severity of 26.6% and disease decrease over control of 49.2%, at a much lower NP concentration than earlier reported studies. Thus, the current report implies using the leaf extract synthesized Ag NP to control and BLB disease management in field conditions.

Keywords: Antibacterial; Bacterial leaf blight; Greenhouse; Leaf extract; Phytopathogen; Rice; Silver nanoparticles; Xanthomonas oryzae pv. oryzae.