Antifungal activity and defense response activation by Co- and Ni-doped ZnO nanoparticles against tomato root rot disease.

Fusarium root rot, caused by Fusarium oxysporum f. sp. radicis-lycopersici, is a severe soil-borne fungal disease that affects tomato production worldwide. This work evaluated Co- and Ni-doped ZnO nanoparticles (NPs) against F. oxysporum f. sp. radicis-lycoperisici, which causes root rot disease in tomatoes, either as resistance inducers or by providing direct antifungal action. The direct antifungal activity of these nanoparticles was evaluated by assessing their ability to inhibit F. oxysporum f. sp. radicis-lycoperisici growth in vitro and reduce disease severity under greenhouse conditions. The induction of resistance was examined by assessing the expression of two pathogenesis- and defense-related genes as well as phenolic compound content in treated tomato plants in response to F. oxysporum f. sp. radicis-lycopersici relative to untreated plants. The effect of Co- and Ni-doped ZnO NPs on the growth characters of tomato plants was also investigated. The growth of F. oxysporum f. sp. radicis-lycopersici was significantly inhibited by the examined nanoparticles and fungicide compared to untreated control. The highest suppression of F. oxysporum f. sp. radicis-lycopersici growth was 98.4%, 98%, and 97% for Co-, Ni-doped ZnO NPs, and fungicide, respectively. Root rot disease severity was significantly reduced in tomato plants treated with Co- and Ni-doped ZnO NPs and fungicide as compared to untreated plants under greenhouse conditions. The results indicated that tomato plants treated with Co-doped ZnO NPs, fungicide and Ni-doped ZnO NPs exhibited higher expression levels of pathogenesis-related protein 1 (PR1) (5, 4.5, and 2.9-fold) and linoleate 9 S-lipoxygenase D (LOXD) (3.5, 3, and 2.7-fold) during F. oxysporum f. sp. radicis-lycopersici infection, compared to untreated infected plants, respectively. Tomato plants treated with Co- and Ni-doped ZnO NPs alongside fungicide showed significant phenolic content compared to untreated plants. Growth parameters of tomato plants significantly increased by treatment with Co- and Ni-doped ZnO NPs and fungicide compared to untreated plants under pathogen stress. Based on our findings, the use of these nanoparticles may present an effective approach for the management of this disease. However, more research is needed to clarify their production costs, efficacy under real field conditions, and ecological effects.