Green synthesis of silver nanoparticles for antifungal activity against tomato fusarium wilt caused by Fusarium oxysporum

Abstract

Fusarium wilt caused by Fusarium oxysporum f. sp. radicis-lycopersici is one of the most important diseases in tomatoes, resulting in severe yield loss and mycotoxin infection in food and feed. The management of Fusarium wilt is based heavily on chemical fungicides, but these chemicals have many environmental concerns. Silver nanoparticles (AgNPs) are gaining importance as emerging resistance-free alternatives of chemical fungicides. In this study, AgNPs were synthesized using the aqueous leaf extract of Viola odorata as a green approach. The antifungal activity of these biosynthesised AgNPs was evaluated in vitro against F. oxysporum using the agar well diffusion method. AgNPs were also evaluated against tomato Fusarium wilt diseases using the foliar spray method in the greenhouse. The characterization of AgNPs revealed that AgNPs were of spherical shape, crystalline in nature, and had an average size of 18 nm. In the antifungal assay, 60 mg/l AgNPs strongly inhibited the growth of F. oxysporum with a growth zone of 18 ± 0.89 mm compared to fungicide (23 ± 1.20 mm) and AgNO₃ (52 ± 2.33 mm). Similarly, 60 mg/l of AgNPs when sprayed on tomato plants in the greenhouse showed a survival rate of about 80% with no observable phytotoxic effect. This study provides a first baseline to control Fusarium wilt in tomato using biosynthesised AgNPs without affecting the health of crops.