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Tomato is a globally important fruit crop, which is easily susceptible to infection by plant-parasitic nematodes during growth. In this study, selenium nanoparticles were biosynthesized through the selenite reduction pathway in a wild-type Pseudomonas stutzeri BB19 and were characterized by uniform nanostructured needle-like forms with an average size of 95.2 nm. The nematicidal effect of biosynthesized selenium nanoparticles (BioSeNPs) at different concentrations (2, 6, and 10 ppm) during the pre- or post-infection of tomato root-knot nematode (RKN), Meloidogyne incognita, was assessed under greenhouse conditions. The BioSeNPs were applied as a foliar spray or a soil drench, compared to ethoprophos nematicide (100 mL/pot). The results showed that the ethoprophos nematicide significantly reduced the number of galls, egg mass, and eggs/egg mass of M. incognita by 94.2, 92.8, and 49.8%, respectively. BioSeNPs, as foliar sprays, significantly reduced the number of galls in post-treated infected tomato plants at 10 ppm and in pre-treated infected tomato plants at 2 ppm by 91.9 and 91.4%, respectively. Concerning the egg mass, BioSeNPs significantly reduced it in pre-treated infected tomato plants at 2 ppm as a foliar spray by 90.9%. Moreover, BioSeNPs significantly reduced the eggs/egg mass in pre-treated infected tomato plants at 2 ppm as a soil drench by 43.3%. On the other hand, the BioSeNPs considerably improved tomato growth, chlorophyll a and b, carotenoid content, and enzymes (i.e., catalase and peroxidase) activity compared to untreated infected tomato plants (negative control). Hence, the BioSeNPs show a significant application potential as a cost-effective and environmentally friendly biocontrol agent for RKN management in tomato plants.

Abstract Background Salvadora persica is an endangered medicinal plant due to difficulties in its traditional propagation. It is rich in bioactive compounds that possess many pharmaceutical, antimicrobial activities and widely used in folk medicine. The current study aims at in vitro propagation of Salvadora persica and the application of different nanoparticles (NPs) to induce the synthesis of bioactive and secondary metabolites within the plant. The cellular and genetic responses to the application of different NPs were evaluated. Results The impact of nanoparticles NPs (ZnO, SiO2, and Fe3O4) on callus growth of Salvadora persica and the production of its active constituent benzyl isothiocyanate was examined, regarding some oxidative stress markers, antioxidant enzymes, and genetic variabilities. An encouraging impact of 0.5 mg/l ZnO NPs on benzyl isothiocyanate production was shown reaching up to 0.905 mg/g callus fresh weight in comparison to 0.539 mg/g in control callus. This was associated with decreasing hydrogen peroxide content and increasing superoxide dismutase and peroxidase activities. The deposition of the NPs on cellular organelles was detected using a transmission microscope. Fifteen Inter-Simple Sequence Repeats (ISSR) primers detected an overall, 79.1% polymorphism among different treatments. A reduction in genomic DNA template stability (GTS) was made and was more pronounced in higher doses of different NPs. Conclusion This study is a stepping stone in developing a productive protocol for in vitro production of benzyl isothiocyanate from Salvadora persica using NPs as a valuable anticancer compound.