Eco-friendly biosynthesis of silver nanoparticles from banana flower extract for protective role against the rice blast pathogen <i>Pyricularia oryzae</i>

Abstract Rice blast caused by Pyricularia oryzae (syn. Magnaporthe oryzae ) is one of the most devastating diseases in rice, resulting in substantial yield loss. Currently, the control of rice blast relies significantly on chemical fungicides, which raise numerous environmental concerns. However, silver nanoparticles (AgNPs) are emerging as innovative, non-resistant substitutes for conventional fungicides. This study aimed to synthesize AgNPs from banana flowers via a green approach and assess their antifungal activity against Pyricularia oryzae strain SP2 in vitro . The pathogen Pyricularia oryzae strain SP2 was identified by morphological features and study of the internal transcribed spacer (ITS) sequence. The AgNPs were characterized via UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive x-ray analysis (EDX). The optimal reaction conditions for the green synthesis of the AgNPs resulted in a rapid color change from light yellow to dark brown when the floral extract (15 ml) was added. A surface plasmon resonance peak was observed in the UV-visible spectrum at approximately 433 cm −1 , which was correlated with the synthesis of the AgNPs. The biogenic AgNPs had a spherical form with an average particle size of 47.63 nm, according to TEM and SEM examination. The greatest mycelial growth inhibition of P. oryzae (87.25%) was observed when it was exposed to biofabricated AgNPs at 40 μg ml −1 . The AgNPs successfully suppressed spore germination and germ tube development of P. oryzae , with increased doses demonstrating enhanced antifungal efficacy. Additionally, the appressorium formation rates decreased from 78.34% in the control to 41.67%, 16.45%, and 4% at increasing concentrations (20, 30, 40 μg ml −1 ). Overall, this study demonstrated that bioinspired AgNPs have antifungal activity against the rice blast pathogen P. oryzae and can be used to control blast diseases in rice.