Foliar spray and seed priming of titanium dioxide nanoparticles and their impact on the growth of tomato, defense enzymes and some bacterial and fungal diseases

Bacterial and fungal pathogens are major constraints in successful cultivation of tomato resulting into rigorous yield losses. The impact of titanium dioxide nanoparticles (TiO2 NPs) on bacteria, i.e. Pseudomonas syringae pv. tomato, Xanthomonas campestris pv. vesicatoria, Pectobacterium carotovorum subsp. carotovorum and Ralstonia solanacearum and fungi Fusarium oxysporum f. sp. lycopersici and Alternaria solani and on the growth of tomato, chlorophyll, carotenoid contents, proline and defense enzymes viz., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) activities were determined. TiO2 NPs were applied at 0.10 mL·L−1 and 0.20 mL·L−1concentration as foliar spray and seed priming. Inoculation of tomato with either of these pathogens reduced plant growth, chlorophyll and carotenoid contents, but increased proline and activities of SOD, CAT, APX and PAL. Maximum increase in plant growth, chlorophyll, carotenoid, proline, SOD, CAT, APX and PAL, and reduction in disease indices was observed at foliar spray with 0.20 mL·L−1 TiO2 NPs, followed by seed priming. Use of 0.10 mL·L−1 NPs as seed priming was less effective. Scanning electron microscopy revealed the absorption of TiO2 NPs by trichomes, stomata and seed surface. Foliar spray with 0.20 mL·L−1 TiO2 NPs was useful in increasing plant growth and provided substantial management of bacterial and fungal diseases of tomato.