Green Synthesis and Characterization of Zinc Oxide Nanoparticles Using Eucalyptus globules and Their Fungicidal Ability Against Pathogenic Fungi of Apple Orchards

Eucalyptus globules belonging to the Myrtaceae family was explored for the synthesis of
zinc oxide nanoparticles and for biological applications. The aqueous extract of the synthesized zinc
nanoparticles (ZnNPs) was characterized using UV-visible spectrophotometer, FTIR, SEM and TEM.
The aqueous broth was observed to be an efficient reducing agent, leading to the rapid formation of
ZnNPs of varied shapes with sizes ranging between 52–70 nm. In addition, antifungal activity of
the biosynthesized ZnNPs was evaluated against major phytopathogens of apple orchards. At 100 ppm
of ZnNPs, the fungal growth inhibition rate was found to be 76.7% for Alternaria mali, followed by 65.4 and 55.2% inhibition rate for Botryosphaeria dothidea and Diplodia seriata, respectively. The microscopic observations of the treated fungal plates revealed that ZnNPs damages the topography of the fungal hyphal layers leading to a reduced contraction of hyphae. This considerable fungicidal property of ZnNPs against phytopathogenic fungi can have a tremendous impact on exploitation of ZnNPs for fungal pest management and ensure protection in fruit crops.