Green synthesis of silver nanoparticles using tomato leaves extract and their entrapment in chitosan nanoparticles to control bacterial wilt.

BACKGROUND: Silver nanoparticles (AgNPs), particularly those entrapped in polymeric nanosystems, have arisen as options to manage plant bacterial diseases. Among biopolymers useful for entrapment of AgNPs, chitosan is promising due to its low cost, good biocompatibility, antimicrobial properties, and biodegradability. The goals of this study were: (i) to greenly-synthesize AgNPs using different concentrations of aqueous extract of tomato leaves followed by AgNPs entrapment with chitosan (CH-AgNPs); (ii) to characterize the optical, structural, and biological properties of the produced nanosystems; (iii) to evaluate the antimicrobial activities of AgNPs and nanomaterials; and (iv) to assess the effectiveness of AgNPs and nanomaterials to control tomato bacterial wilt caused by Ralstonia solanacearum.

RESULTS: Spherical and oval AgNPs had incipient colloidal instability, but concentration of tomato leaves extract influenced size (<87 nm) and PdI. Nanomaterials (<271 nm in size) were characterized by a highly stable matrix of chitosan containing polydisperse AgNPs. Free AgNPs and CH-AgNPs were stable for up to 30 days, with no significant alteration in physicochemical parameters. The AgNPs and nanomaterials had antibacterial activity and decreased bacterial growth at micromolar concentrations after 48 h. Morphological changes in R. solanacearum cells were observed after treatment with CH-AgNPs. The application of CH-AgNPs at 256 μM reduced bacterial wilt incidence in a partially resistant tomato genotype, but not in the susceptible line.

CONCLUSION: Greenly-synthesized chitosan-derived nanomaterials containing AgNPs produced with leaves extract from the own species seem a promising and sustainable alternative in an integrated management approach to reduce yield losses caused by bacterial wilt. This article is protected by copyright. All rights reserved.