Influence of Nutrient Medium Composition for Culturing Bacteria and the Dose of <i>B. subtilis</i> 10-4 Biologics on Growth Indicators and Productivity of Wheat Plants

Abstract

Inoculation of crop seeds with selective strains of growth-stimulating bacteria is an environmentally friendly, low-cost way to increase their yield, but may depend on some biotechnological factors affecting their physiological activity. These include the conditions for the cultivation of bacteria and the dose of the drug. The work analyzed the effectiveness of inoculation of Bashkir spring wheat with 28 different preparations of the Bacillus subtilis strain 10-4: 1 - an aqueous suspension of bacterial cells washed off potato-glucose agar (PGA), 2 - a liquid culture containing cells with exometabolites obtained by cultivating bacteria in potato- glucose broth (PGB), 3 - liquid culture of bacterial cells grown in legume-glucose broth (LGB). At the same time, the growth-stimulating effect of applying a high dose (108 cells/ml) and a low dose (104-105 cells/ml) of bacteria in the inoculum was evaluated. When comparing the preparations obtained from potato-glucose medium, it was revealed that the positive growth effect (an increase in the number of wheat plant roots) was caused only by a high dose of the drug cells in the PGA and both doses of the drug in the PGB, but a high dose of the drug in the PGB inhibited seed germination up to 74% (in the control 100%). When comparing the preparations obtained during the cultivation of bacteria in PGB and LGB, it was revealed that the best growth effect (total root length and shoot height) was greater than control in plants inoculated with a small dose of the drug in PGB and a large dose of the drug in LGB. The stimulating effect of a small dose of the drug in LGB was less and extended only to the root system. The results of laboratory experiments coincided with the effectiveness of the studied drugs in the field. The use of a drug obtained in BGO and administered at a dose of 108 cells / ml, and a drug obtained in PGB and administered at a dose of 105 cells/ml, increased grain yield by 1.6-1.7 times with a decrease in the intensity of leaf-stem diseases by 32 and 11% compared with the untreated control. The drug obtained in LGB and introduced in a small dose did not provide either an increase in yield or a protective effect compared to the control. Possible causes of the action of B. subtilis 10-4 strain preparations related to the production of phytohormones by it, depending on the composition of the medium, and with different adaptive capacity of bacteria when cultured on nitrogen-rich and less nitrogen-rich media are discussed.