Green Silver Nanoparticles and Their Activity as Antifungal Agents Against <i>Penicillium digitatum</i> Causing Green Mould of Citrus

Abstract The green synthesis of silver nanoparticles (SNPs) using aqueous extracts of five plants viz., Ocimum americanum , Azadirachta indica , Allium sativum, Eucalyptus hybrida , Zingiber officinale were evaluated for their antifungal property against Penicillium digitatum , a green mould pathogen of citrus fruits. The five plant species were selected from a screening of aqueous extracts from 16 plant species. The efficacy of aqueous extracts, at 50 % concentration, ranged from 14.44–68.52 % inhibition in mycelia growth of P. digitatum . Among SNPs, O. americanum was found most efficacious, at 1000 ppm concentration, with 80.7 % mycelial inhibition followed by A. indica with 77.4 % mycelial growth inhibition of fungal pathogen. Further, physical and structural characterization of SNPs of O. americanum and A. indica was carried out. The characterization analysis executed via transmission and scanning electron microscope revealed size distribution and nanoparticles were spherical to irregularly shaped ranging from 22.8–250 nm in O. americanum and 26.5–500 nm in A. indica . In UV‐visible spectrophotometer, the absolute absorption peak was recorded at 448 nm and 442 nm for O. americanum and A. indica , respectively. FTIR analysis of SNPs of A. indica and O. americanum confirmed the presence of carboxyl, amide group and secondary amines which were the main constituent of proteins. The novelty of the present study is in the green synthesis of silver nanoparticles with potential in the management of postharvest pathogens of fruit crops. The synthesis of SNPs used in this study is simple, environmentally benign and cost‐effective using aqueous extract of native plants.