Antifungal Efficacy of Cu-Based Nano-Chitosan on Rhizopus stolonifer, A Virulent Phytopathogen

Abstract

Agro-scientists are giving endless efforts for synthesizing a bio-derived molecule that can act as a promising antifungal agent for combating a large number of phytopathogens. Harmful phytopathogens decrease crop yield and its quality. Rhizopus stolonifer is one such virulent phytopathogen that causes huge losses during the post-harvest period of crops. This pathogen mainly causes rot disease in fruits, crops, and vegetables. The second most abundantly available biological macromolecule, Chitosan and its metal-based nanoparticles stands as a potential antifungal agent for combating Rhizopus stolonifer. This study includes the synthesis of Cu chitosan nanoparticles (Cu-CNPs) and chitosan nanoparticles (CNPs) through the ionic gelation method and its characterization based on UV Vis spectrophotometer, FE-SEM, EDXS, and DLS. Cu-CNPs and CNPs were screened from 100-2000 µg/mL concentration against R. stolonifer for the assessment of its antifungal activity. Spore viability assay and lipid peroxidation of the pathogen using Cu-CNPs and CNPs were also determined. Generation of oxidative stress in the mycelium of the pathogen on the application of Cu-CNPs and CNPs was traced by fluorescence microscopy. Changes in the ultra-structure of the sporangium of R. stolonifer after treatment with Cu-CNPs and CNPs were visualized under SEM. Results showed that Cu-CNPs inhibit the growth of R. stolonifer at 2000 µg/mL and elevate malonaldehyde (MDA) content in the pathogen as a result of lipid peroxidation and produces defined damages on the sporangium membrane as observed under electron microscope. Fluorescence microscopy revealed the emission of high intensity of fluorescence due to the generation of oxidative stress in Cu-CNPs treated fungal mycelium.