Abstract
The present study is focused on the extracellular synthesis of silver nanoparticles (AgNPs) using culture supernatant of an agriculturally important bacterium, Serratia sp. BHU-S4 and demonstrates its effective application for the management of spot blotch disease in wheat. The biosynthesis of AgNPs by Serratia sp. BHU-S4 (denoted as bsAgNPs) was monitored by UV–visible spectrum that showed the surface plasmon resonance (SPR) peak at 410 nm, an important characteristic of AgNPs. Furthermore, the structural, morphological, elemental, functional and thermal characterization of bsAgNPs was carried out using the X-ray diffraction (XRD), electron and atomic microscopies, energy dispersive X-ray (EDAX) spectrometer, FTIR spectroscopy and thermogravimetric analyzer (TGA), respectively. The bsAgNPs were spherical in shape with size range of ∼10 to 20 nm. The XRD and EDAX analysis confirmed successful biosynthesis and crystalline nature of AgNPs. The bsAgNPs exhibited strong antifungal activity against Bipolaris sorokiniana, the spot blotch pathogen of wheat. Interestingly, 2, 4 and 10 µg/ml concentrations of bsAgNPs accounted for complete inhibition of conidial germination, whereas in the absence of bsAgNPs, conidial germination was 100%. A detached leaf bioassay revealed prominent conidial germination on wheat leaves infected with B. sorokiniana conidial suspension alone, while the germination of conidia was totally inhibited when the leaves were treated with bsAgNPs. The results were further authenticated under green house conditions, where application of bsAgNPs significantly reduced B. sorokiniana infection in wheat plants. Histochemical staining revealed a significant role of bsAgNPs treatment in inducing lignin deposition in vascular bundles. In summary, our findings represent the efficient application of bsAgNPs in plant disease management, indicating the exciting possibilities of nanofungicide employing agriculturally important bacteria.
Highlights
Agricultural production is constantly suffering from plethora of threats instigated by various classes of plant pathogens leading to huge economic losses
The bacterial strain BHU-S4 was isolated from agricultural soil with the aim of exploiting its AgNPs synthesizing potential for agricultural purposes
The atomic force microscope (AFM) images showed the irregular spherical surface morphology of bsAgNPs in the size range of,8 to 22 nm (Figure 3D and 3E), which is in accordance with the results obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)
Summary
Agricultural production is constantly suffering from plethora of threats instigated by various classes of plant pathogens leading to huge economic losses. Innovative technologies are being introduced in modern agriculture to minimise such losses. Among such technological innovations, nanotechnology is gathering noteworthy considerations due to its robust applications in agriculture [1,2]. Nanoparticles have attracted considerable attention in the fields of medicine, pharmaceuticals, cosmetics and electronics due to unique physical, chemical and biological properties [3]. The development and application of biosynthesized nanoparticles has opened new avenues in agricultural research oriented to developing ecofriendly and effective means of controlling plant diseases. Biological synthesis of silver nanoparticles (AgNPs) has offered a consistent, non toxic and ecofriendly approach for plant disease management due to their strong antimicrobial properties [4,5,6]
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