Silver nanoparticle synthesis using neem leaf extract and its conjugation to fluconazole for tomato early blight treatment

Abstract

Tomato is a vital vegetable ranked 2nd after Solanum tuberosum. It may be affected by the early blight caused by Alternaria solani, resulting in crop yield reduction. This investigation was conducted to check the efficacy of conjugated silver–fluconazole nanoparticles in combating early blight in tomatoes. Silver nanoparticles (AgNPs) were synthesized by using the leaf extract of Azadirachta indica. Fluconazole nanoparticles (FLZ-NPs) were developed by the antisolvent precipitation method. AgNPs were conjugated to FLZ-NPs. Silver, fluconazole, and conjugated silver–fluconazole nanoparticles were identified and characterized based on shape, morphology, and size with a scanning electron microscope, UV–visible spectrophotometer, X-ray diffraction, and particle size analyzer. Both silver and conjugated nanoparticles had spherical shapes and were crystalline, but with varying sizes of 64.4 and 95.6 nm, respectively. Tomato seedlings were artificially infected with A. solani and treated with various amounts of AgNPs, FLZ-NPs, and AgNPs–FLZ-NPs. Post-7 days of treatment, the amounts of total reducing sugars, total chlorophylls, total phenols, peroxidase, catalase, peroxidase, glutathione reductase, phenylalanine ammonia-lyase, and superoxide dismutase were quantified. The conjugation increased the efficacy of fluconazole drug in eradicating the early blight in tomatoes as an important elevation in all the above tested biochemical parameters was noticed. It also showed better results than its individual application. This overall augmentation of biochemical aspects has a vital role in the defense mechanism of plants against early blight infection. Therefore, the designed Ag–FLZ nanoparticles can be utilized to combat the early blight infection on tomato plants caused by A. solani.