Title: Effect of silicon dioxide nanoparticles on bacterial pathogens, growth and some biochemical aspects of tomato

Abstract

The effects of seed priming and foliar spray with silicon dioxide nanoparticles (SiO2 NPs) in two concentrations (0.10 and 0.20 gL−1) was observed on plant growth parameters, total chlorophyll and carotenoid contents, proline and activities of defense enzymes (superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia lyase (PAL) and ascorbate peroxidase (APX) in tomato with / without bacterial pathogens i.e. Xanthomonas campestris pv. vesicatoria (Xcv), Pectobacterium carotovorum subsp. carotovorum (Pcc) and Ralstonia solanacearum (Rs), under greenhouse conditions. The efficacy of SiO2 NPs solutions (0.10 and 0.20 gL−1) was tested separately against all three bacterial pathogens under in vitro conditions. Concentration of NPs and mode of application were the determining factors for the NPs efficacy in disease suppression and plant growth improvement. Foliar spray was more effective than seed priming in increasing plant growth, total chlorophyll and carotenoid contents, proline and defense enzymes in the presence and absence of bacteria. Foliar spray of 0.20 gL−1 SiO2 NPs caused highest increase in all parameters and maximum reduction in disease indices. In vitro tests by disc diffusion method and scanning electron microscopy revealed antimicrobial nature of SiO2 NPs with varied adverse effects on tested pathogens. Broader inhibition zone (9.26 mm) was formed against Rs followed by Pcc (8.12 mm) and Xcv (7.37 mm). Plants foliar sprayed with 0.20 gL−1 SiO2 NPs showed highest increase in plant growth and biochemical parameters against tested bacteria. Thus, 0.20 gL−1 SiO2 NPs solution can be recommended for the control of these bacterial pathogens. However, it will be interesting to explore this dose of NPs under field conditions.