The study aims to establish the effect of nanoselenium on the growth and antagonistic activity of the Lactobacillus casei IMB B-7343 and Lactobacillus plantarum IMB B-7344 strains against the phytopathogenic bacterium Xanthomonas campestris B-4102. Selenium nanoparticles were obtained by reducing a solution of sodium selenite with L-cysteine in the presence of sodium alginate. The cultivation of Lactobacilliwas carried out in a MRS nutrient medium with the addition of a colloidal solution of nanoselenium at the following concentrations: 0.05; 0.1; 0.15; 0.2 and 0.25 mg/l (for selenium). Bacteria were cultured in a 96-well plate in a Multiskan FC photometer at 36 ºС under constant shaking. The antagonistic activity of the strains was studied by the method of agar blocks. It was found that the addition of nanoselenium to the nutrient medium at a concentration of 0.2 to 0.25 mg/l contributed to a decrease in the duration of the exponential growth phase by an average of 3 hours, as well as to a decrease in the biomass accumulation of the L. casei IMB B-7343 strain by 15.0%. The optical density of this strain culture was observed to increase by 15.9% in the stationary growth phase under the addition of a nanoselenium solution to the nutrient medium at a concentration of 0.15 mg/l. During the cultivation of the L. plantarum IMB B-7344 strain in an MRS nutrient medium with the addition of a colloidal solution of nanoselenium at a concentration of 0.05–0.25 mg/l in the exponential development phase, an acceleration of the culture growth on average by 5 hours relative to the control was observed. It was noted that, upon the addition of nanoselenium to the nutrient medium, an increase in the antagonistic activity of lactobacillus strains against the phytopathogenic bacterium X. campestris B-4102 was observed, particularly in the L. plantarum IMB B-7344 strain (the zone of inhibition of the phytopathogen growth was 14.5–15 mm).
The excessive use of pesticides is a problem in most parts of the world today because of their broad and unspecific target range that is considerably harmful. The accumulation of several chemical insecticide residues based on chlorpyrifos-methyl, organochlorine, different isomers of HCH, DDT etc., in Triticum aestivum L. plants can be dangerous. Hence, there is an urgent need to develop potential and safer alternative measures. Wheat (Triticum aestivum L.) is a major cereal crop grown and used for food, animal feed, beverages and furniture accessories in most parts of the world. It also serves as a host to various insect pests. Our previous studies showed the insecticidal potency and specificity of short ssDNA oligonucleotides from the inhibitor of apoptosis (IAP-2 and IAP-3) genes of Lymantria dispar multicapsid nuclear polyhedrosis virus (LdMNPV) against gypsy moth (L. dispar) larvae, a possible insect pest of non-host plants like wheat. Consequently, the present study analyzes the effects of ssDNA oligonucleotides used as DNA insecticides on wheat (T. aestivum) plant biomass, plant organs and some biochemical parameters as a marker of the safety margin on non-target organisms. The results obtained on plant biomass showed that groups treated with ssDNA oligonucleotides at concentrations of 0.01 pmol • µl −1 , 0.1 pmol • µl −1 and 1 pmol • µl −1 varied in comparison with the control group, but remained harmless to plant growth and development, while the treatment concentration of 0.001 pmol • µl −1 did not affect the plant biomass. The glucose, protein and phosphorous biochemical parameters, analyzed after 21 days, showed that the ssDNA oligonucleotides used were equally safe. The data obtained for the plant organs (leaves and root lengths) indicate that the phenomenon of DNA insecticides can be further studied and developed for plant protection while improving the growth of plant organs even for a non-target organism such as wheat T. aestivum plants.
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