Antifungal Activity of Copper Oxide Nanoparticles against Root Rot Disease in Cucumber

Metal oxide nanoparticles have recently garnered interest as potentially valuable substances for the management of plant diseases. Copper oxide nanoparticles (Cu2ONPs) were chemically fabricated to control root rot disease in cucumbers. A scanning electron microscope (SEM), X-ray diffraction (XRD) and photoluminescence (PL) were employed to characterize the produced nanoparticles. Moreover, the direct antifungal activity of Cu2ONPs against Fusarium solani under laboratory, greenhouse, and field conditions were also evaluated. In addition, the induction of host-plant resistance by Cu2ONPs was confirmed by the results of enzyme activities (catalase, peroxidase, and polyphenoloxidase) and gene expression (PR-1 and LOX-1). Finally, the effect of Cu2ONPs on the growth and productivity characteristics of the treated cucumber plants was investigated. The average particle size from all the peaks was found to be around 25.54 and 25.83 nm for 0.30 and 0.35 Cu2O, respectively. Under laboratory conditions, the study found that Cu2ONPs had a greater inhibitory effect on the growth of Fusarium solani than the untreated control. Cu2ONP treatment considerably reduced the disease incidence of the root rot pathogen in cucumber plants in both greenhouse and field environments. Defense enzyme activity and defense genes (PR1 and LOX1) transcription levels were higher in cucumber plants treated with Cu2ONPs and fungicide than in the untreated control. SEM analysis revealed irregularities, changes, twisting, and plasmolysis in the mycelia, as well as spore shrinking and collapsing in F. solani treated with Cu2ONPs, compared to the untreated control. The anatomical analysis revealed that cucumber plants treated with Cu2ONPs had thicker cell walls, root cortex, and mesophyll tissue (MT) than untreated plants. Cucumber growth and yield characteristics were greatly improved after treatment with Cu2ONPs and fungicide. To the best of our knowledge, employing Cu2ONPs to treat cucumber rot root disease is a novel strategy that has not yet been reported.