In order to achieve the optimal number of colony forming units and a high level of antifungal metabolites synthesis, we carried out the periodic cultivation of the Bacillus subtilis BZR 336 g and Bacillus subtilis BZR 517 strains at various pH and temperature levels. In the experiment for determining the optimal temperature, the maximum titer of B. subtilis BZR 336 g bacterium (1.6-1.7 × 109 CFU/ml) was recorded at a cultivation temperature of 20-25 °C. For B. subtilis BZR 517 strain, the temperature turned out to be optimal at 30 °C: the titer was 8.9 × 108 CFU/ml. The maximum antifungal activity of B. subtilis BZR 336 g strain against the test culture of Fusarium oxysporum var. orthoceras was observed at a cultivation temperature of 20-25 °C; for B. subtilis BZR 517 strain, 25-30 °C. When determining the optimal pH level, it was found that a high titer of B. subtilis BZR 336 g strain cells was determined at pH 8.0 (2.7 × 109 CFU/ml), for B. subtilis BZR 517 strain it was at pH 6.0-8.0 (1.0 × 109 CFU/ml). The maximum antifungal activity was noted with the same indicators. Chromatographic and bioautographic analyses suggest that the synthesized antifungal metabolites belong to surfactin and iturin A. The data obtained in this research can be used in the development of the technology for the production of effective biofungicides to protect crops against Fusarium pathogens.

Root-knot disease caused by Meloidogyne incognita leads to significant crop yield losses that may be aggravated by the association with pathogenic fungi and bacteria. Biological agents can be effectively used against the complex disease of root-knot nematode and pathogenic fungi. In this study, 35 bacterial strains were analyzed for their in vitro nematicidal, antagonistic and growth stimulation activities. Based on results from the in vitro assays, grow-box experiments on tomato and cucumber were carried out with the strain BZR 86 of Bacillus velezensis applied at different concentrations. Effects of B. velezensis BZR 86 on the development of root-knot disease were evaluated by recording root gall index, number of galls and number of eggs in egg masses. Application of B. velezensis BZR 86 noticeably decreased the development of root-knot disease on tomato and cucumber plants, as well as significantly increased growth and biomass of cucumber plants in accordance with bacterial concentration. This study seems to demonstrate that strain B. velezensis BZR 86 could be an additional tool for an environmentally safe control of root-knot disease on horticultural crops.

ISOLATION AND CHARACTERIZATION OF ANTIFUNGAL METABOLITES OF Bacillus subtilis STRAINS BZR 336G AND BZR 517 USING THE MODIFIED BIOAUTHOGRAPHY METHOD Т.М. Sidorova, А.М. Asaturova, A.I. Homyak, N.S. Tomashevich

Fungi of the genus Fusarium are economically significant pathogens in most wheat-growing regions worldwide. The biocontrol agents Bacillus velezensis BZR 336 g and BZR 517 were tested for growth inhibition of F. graminearum BZR 4. The results demonstrated that the strains are capable of deforming and destroying hyphae. The modified bioautography technique showed that the strains produce iturin A and surfactin, which probably explains the mechanism of pathogen inhibition. Furthermore, lipopeptides were detected and identified in two samples by the HPLC-HRMS. Compounds such as surfactin and their isomers and homologues were found in both samples. An experiment on an artificial infectious background in a climatic chamber established that the biological effectiveness of strains is close to that of chemical and biological references. Cultivation of plants with B. velezensis showed that the strains are likely to reduce the stress load. An efficacy of up to 45.0% was determined for bioagents BZR 336 g and BZR 517 in field trials, while the yield was up to 7.9 t/ha. The use of B. velezensis BZR 336 g and BZR 517 as biocontrol agents provides an environmentally friendly approach to the control of Fusarium rots on wheat, reduction of the pesticide load, and hence quality harvest.

Bacillus velezensis strain BZR 336g is a plant growth-promoting rhizobacterium isolated from a winter wheat rhizoplane from the Krasnodar region in Russia. In this study, we report the genome, including genes with known phenotypic function, i.e., the biosynthesis of secondary metabolites with fungicidal and plant growth-promoting activities. We sequenced and analyzed the complete BZR 336g genome using two different DNA preparation methods to help us better understand the origin of the antimicrobial and antifungal abilities and to weigh the biocontrol properties of this strain.

This paper investigates the antagonistic and plant growth promotion activity of the new indigenous bacteria antagonist strains P. chlororaphis BZR 245-F and Pseudomonas sp. BZR 523-2. It was found that on the 10th day of cultivation, BZR 245-F and BZR 523-2 exhibit an antagonistic activity against F. graminearum at the level of 59.6% and 15.1% and against F. oxysporum var. orthoceras at the level of 50.2% and 8.9%, respectively. Furthermore, the BZR 523-2 strain stimulated the growth of winter wheat seedlings more actively than the BZR 245-F strain. When processing seeds of winter wheat, Pseudomonas sp. BZR 523-2 indicators were higher than in the control: plant height increased by 10.3%, and root length increased by 18.6%. The complex characteristic properties of the metabolite were studied by bioautography and HPLC-MS. Bioautography proved the antifungal activity of phenazine nature compounds synthesized by the new bacterial strains. We qualitatively and quantitatively analyzed them by HPLC-MS analysis of the strain sample metabolites. In the BZR 245-F sample, we found more phenazine compounds of various types. Their total phenazine concentration in the BZR 245-F was more than five times greater than in the BZR 523-2. We defined crucial differences in the quantitative content of the other metabolites. Despite the difference between new indigenous bacteria antagonist strains, they can be used as producers of effective biopesticides for sustainable agriculture management.