This article aims to study the influence of the culture of the Bacillus thuringiensis var. thuringiensis 888 on the quality of the vegetative mass of Origanum vulgare in terms of the number of antioxidants and flavonoids, yield and composition of the essential oil. The research material included a liquid spore culture of the B. thuringiensis 888 strain, samples of oregano: sample no. g-4, containing 52.0% carvacrol in essential oil; No. 2 containing 59.85% α-terpineol; No. 1 with a predominant content of germacrene D (21.5%) and β- caryophyllene (19.4%). Soluble carbohydrates in the plants were determined using M.S. Dubois’s method, flavonoids – spectrophotometrically at 420 nm following R.A. Bubenchikov’s method. The total content of antioxidants was determined using the reduction of iron(III) chloride to iron(II) chloride. The essential oil content of Origanum vulgare was determined by using hydrodistillation following A.S. Ginsberg. Gas chromatography was used to determine component composition of the essential oil. The results show that treating the O. vulgare samples with the spore culture of B. thuringiensis 888 strain culture does not significantly affect the accumulation of terpenoid quinones, tochromanols and water-soluble antioxidants in leaves. It has been shown that treating oregano with an ordinary liquid spore culture of the B. thuringiensis 888 strain promotes the formation of a persistent tendency towards the accumulation of reducing sugars in the vegetative mass of plants — up to 30.8% compared to the control. Treating plants with a culture of B. Thuringiensis 888 strain promoted an increase in the essential oil content in O. vulgare plants of the sample no. 1 by 2.4 times, as compared to the control and did not significantly affect the essential oil content of the samples no. 2 and no. g-4. The sample no. g-4 was the most resistant to treatment with entomopathogenic bacteria, and the content of linalool and caryophyllene oxide in essential oils decreased by 44.6 and 37.1%, respectively, and linalyl acetate by 4.3 times compared with the control, as well as the accumulation of α-terpineol by 86.1%.

Although the entomopathogenic bacteria Bacillus thuringiensis Berliner are well-known bio-agents for regulating the population of leaf-eating pests of agricultural and ornamental crops, other agricultural properties of this microorganism are promising. In this work, the growth-stimulating effect of entomopathogenic strains of B. thuringiensis on Deviz pea plants was studied. The entomopathogenic strains B. thuringiensis 685, 926 and 109-C obtained from the Crimean Collection of Microorganisms of the Crimean Agricultural Research Institute, registered online (http://www.ckp-rf.ru) with number 507484, were used as research material. The morphometric parameters of pea sprouts were evaluated following standard methods. Biochemical parameters of pea sprouts were determined for 10-day-old sprouts. The amylase activity of pea sprouts was determined by photocalorimetry; total acidity was measured by titration using 0.1 n NaOH solution; total water-soluble phenolic compounds were determined by Leventhal titrimetric method. It was found that liquid spore culture of strains B. thuringiensis 685, 926 and 109-C had a stimulating effect on the length of root and stem and the weight of 10-day-old sprouts of Deviz pea variety. Treatment with a spore suspension of all tested strains B. thuringiensis led to an increase in the content of organic acids in the sprouts by an average of 12.4% compared with that of the control. Maximum stimulating effect on amylolytic activity and synthesis of phenolic compounds in Deviz pea sprouts was achieved by treating with a spore suspension of the strain B. thuringiensis 926. The amylase activity increased on average by 41.5% when compared to that of the control, while the total content of phenolic compounds in this experiment was 2.3 times higher than that of the control. Therefore, in light of the entomopathogenic properties and the obtained data on the growth-stimulating activity of the strains of B. thuringiensis, it can be concluded that these bacteria have additional potential for their use in agriculture as a bio-agent for plant protection having a complex action.