Effect of Silver Oxide Nanoparticles on Growth, Activities of Defense Enzymes and Fungal and Bacterial Diseases of Tomato

Silver oxide nanoparticles (Ag₂O NPs) were synthesized from solid homogeneous solution of silver oxide material. X‑ray diffraction pattern, energy dispersive spectroscopy spectra, scanning electron and transmission electron microscopy revealed 38.23 nm size. Effect of synthesized Ag₂O NPs was observed as foliar spray and seed priming in two concentrations i.e. 0.10 and 0.20 gL⁻¹ on bacterial and fungal diseases of tomato. Scanning electron microscopy revealed disturbed shape of conidia, bacterial cells and fragmented mycelium of pathogens i.e. Pseudomonas syringae pv. tomato (Pst), Xanthomonas campestris pv. vesicatoria (Xcv), Pectobacterium carotovorum subsp. carotovorum (Pcc), Ralstonia solanacearum (Rs), Fusarium oxysporum f. sp. lycopersici (Fol) and Alternaria solani (As). In vitro study also revealed adverse effects of Ag₂O NPs on fungal and bacterial test pathogens. Foliar spray of NPs caused a greater increase in plant growth, carotenoids, chlorophyll, proline and defense enzymes activities i.e. catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) than seed priming both in the presence and absence of test pathogens. Disease suppression of tomato and increase in plant growth was Ag₂O NPs concentration dependent. Foliar spray of 0.20 gL⁻¹ NPs reduced disease indices to the utmost, and caused highest increase in plant growth parameters, chlorophyll, carotenoid and proline contents. Role of Ag₂O NPs in disease containment and plant growth augmentation was also revealed by principal component analysis.