Silver nanoparticles eliminate Xanthomonas campestris pv. campestris in cabbage seeds more efficiently than hot water treatment

Abstract Silver nanoparticles (AgNPs) and the standard hot water treatment (HWT) method were examined as measures against the bacterium Xanthomonas campestris pv. campestris (Xcc). Three sizes (∼2 nm, ∼22 nm and ∼29 nm) of AgNPs were synthesized and characterized using transmission electron microscopy and dynamic light scattering. To evaluate the direct effect of the synthesized AgNPs on Xcc, an in vitro colony counting assay was carried out. Cabbage seeds (cv.’ Avak F1’) were inoculated with an Xcc (strain 1279a) suspension and treated with hot water or a AgNP solution. The Xcc infestation in the young seedlings was quantified using real-time PCR and dilution plating assays. The results of the colony counting assay indicated that the antibacterial effect of the AgNPs depended on the size and concentration of the NPs. The seedling analysis showed that all three sizes of AgNPs suppressed Xcc infestation at concentrations of 6.25 µg·mL−1 and higher. HWT also had an antibacterial effect; nevertheless, in contrast to AgNP treatment, HWT strongly decreased the germination rate of treated seeds.