Exploring the Impact of Bioformulated Copper Oxide Nanoparticles on Cytomorphology of Alternaria brassicicola.

Black leaf spot of Brassica species is caused by a foliar pathogen Alternaria brassicicola (A. brassicicola), the noxious killer of mustard, cabbage, and cauliflower crops. The current investigation involved the synthesis of copper oxide nanoparticles (CuO NPs) from potential strain of Trichoderma harzianum (T. harzianum). Characterization of CuO NPs was performed by UV-vis, FTIR, XRD, SEM-EDX, and HR-TEM studies. UV-visible spectra showed an absorption peak at 275 nm. FTIR study revealed the presence of N-H bonds which could be due to the presence of enzymes and secondary metabolites released in the filtrate of T. harzianum. SEM and HR-TEM revealed the cube shape CuO NPs formed and average particle size was in the range of 31-45 nm. Poisoned food technique was used to check the antifungal efficacy of CuO NPs against A. brassicicola at various concentrations (0.025, 0.050, 0.1, and 0.15 mg/mL). In vitro assays carried on potato dextrose agar showed maximum antifungal activity at 0.15 mg/mL. The control sample have cylindrical and oblong shape conidia, while transverse septation was 2-4 in untreated population. The lower concentrations of CuO NPs (0.025 and 0.050 mg/mL) caused malformed spherical shape conidia with excessive septation, while its higher concentrations (0.1 and 0.15 mg/mL) leads to viability loss in fungal culture. Results indicated that a higher concentration of CuO NPs serve as an effective biocidal concentration for the control of phytopathogens.