Features of the Bacillus thuringiensis 888 strain’s influence on the content of essential oil, antioxidants and flavonoids in Origanum vulgare L.

Abstract: 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%.