Lychee (Litchi chinensis Sonn.) is a famous fruit species of tropical and subtropical regions of the world and many biotic and abiotic stresses affect its yield. In this study, lychee fruit rot has been observed and its incidence has been controlled by using zinc oxide nanoparticles (ZnO NPs). Diseased lychee fruits were collected and diagnosed to identify disease-causing pathogens. Morphological appearance, microscopic observation, and sequence analysis of the amplified ITS region identified this isolated pathogen as Aspergillus niger. To control this problem, ZnO NPs were prepared in the leaf extract of Azadirachta indica. Before their antifungal activity, ZnO NPs were characterized using sophisticated approaches. FTIR revealed the presence of reducing and stabilizing molecules on ZnO NPs including alcohol, carboxylic acid, alkyl halide, amine, and alkyl halide. Crystalline nature and average size (29.024 nm) of synthesized ZnO NPs were described by X-ray diffraction. EDX analysis depicted the mass percentage of zinc (30.15%) and oxygen (14.90%). SEM analysis displayed the irregular shape of nanoparticles and confirmed the nano-size of ZnO NPs. Maximum mycelial growth inhibition (70.5%) was observed at 1.0 mg/mL concentration of ZnO NPs in vitro. In in-vivo disease-control analysis, maximum control of lychee fruit rot disease was observed at the same concentration. These results reveal the potential use of these ZnO NPs on a larger scale to replace hazardous chemical fungicides.
Keywords: Aspergillus niger; Azadirachta indica; ZnO NPs; fruit rot; lychee.