Streptomycetes are known as producers of bioactive substances, particularly antibiotics. Streptomyces netropsis IMV Ac-5025 simultaneously produces different classes of antibiotics, including polyene compounds, phytohormones, and sterols, but the metabolic pathways involved in their biosynthesis are largely understudied. The aim of this work was to explore the biosynthesis of polyene antibiotics, sterols, and phytohormones when the producer is cultivated in a nutrient medium supplemented with exogenous β-sitosterol. Gas chromatography and high-performance liquid chromatography were applied to analyze the spectrum of bioactive compounds. The obtained results demonstrated not only an increase in the accumulation of biomass but also polyene antibiotics, intracellular sterols, auxins, and cytokinins, when cultivating S. netropsis IMV Ac-5025 in a liquid medium with the addition of β-sitosterol. The amount of biomass raised 1.5–2-fold, whilst the sum of polyene antibiotics increased 4.5-fold, sterols’ sum (ergosterol, cholesterol, stigmasterol, β-sitosterol, and 24-epibrassinolide) by 2.9-fold, auxins’ sum (indole-3-acetic acid, indole-3-acetic acid hydrazide, indole-3-carbinol, indole-3-butyric acid, indole-3-carboxaldehyde, and indole-3-carboxylic acid) by 6-fold, and cytokinins’ sum (zeatin, isopentyladenine, zeatin riboside, and isopentenyladenosine) by 11-fold. Thus, we put forward the hypothesis that β-sitosterol plays a regulatory role in the network of biosynthetic reactions of S. netropsis IMV Ac-5025.

The impact of bioformulations on the development of fungal diseases and the productivity of tomatoes was studied. Microorganisms of the genera Azotobacter, Bacillus, Pseudomonas, Streptomyces, and Trichoderma were used as bioagents. Their protective effect was compared with the effectiveness of chemical fungicides. The majority of bioformulations actively inhibited the spore germination of tomato pathogens Alternaria solani and Phytophthora infestans. In greenhouse experiments, biological preparations provided a protective effect at the level of 33.2%–70.1% against early dry spot and 34.3%–65.5% against late blight of tomatoes. The use of bioformulations in the field experiments effectively controlled tomato diseases and improved productivity and fruit quality. The highest protective effect against early dry spot was observed with the use of bioformulations Avercom, Biophosphorin, Haupsin, Planriz, and Trichodermin. Biophosphorin, Azotobacterin, Azostrept, and Haupsin were more effective against phytophthora. Usage of bioformulations provided the 19%–66% increase of healthy fruit harvest of different varieties of tomatoes.

Introduction: Streptomyces species are renowned for producing bioactive natural products, particularly those that induce plant resistance against pathogens and nematodes. This study aimed to investigate the ability of metabolic bioproducts from Streptomyces netropsis IMV Ac-5025, Streptomyces violaceus IMV Ac-5027, and Streptomyces avermitilis IMV Ac-5015 to affect RNAi-mediated resistance in tomato plants against the root-knot nematode. Methods: Spectrodensitometric Thin-Layer Chromatography (TLC), High-Performance Liquid Chromatography (HPLC), and Gas Chromatography (GC) were used to identify natural products of streptomycetes. The resistance of tomato plants to Meloidogyne incognita was evaluated through artificial nematode inoculation coupled with phenological viability assessment. The extent of si/miRNA-driven gene silencing was determined via dot blot hybridization and inhibition of protein synthesis in a wheat germ cell-free translation system. Results: Soil-derived Streptomyces strains were shown to produce diverse bioactive compounds, including antibiotics, lipids, phytohormones, and sterols, and novel bioproducts were developed based on their secondary metabolites (Phytovit, Violar, Averkom, and Averkom nova). Incorporation of these bioproducts into the nutrient medium significantly improved shoot regeneration rates in isolated plant explants. Dot blot hybridization and translational inhibition assays in a wheat germ cell-free system confirmed their phytoprotective effect via the RNA interference mechanism. In vitro cultivation of tomato plants supplemented with biotreatment resulted in a marked enhancement of resistance to M. incognita . Discussion: The secondary metabolic complexes produced by Streptomyces strains promote plant growth and development while enhancing immunity and supporting the efficient operation of signaling networks involved in cellular responses to nematodes. Their activity is mediated through elicitor signals that trigger the de novo synthesis of plant si/miRNAs, which confer protection against M. incognita . These findings highlight the potential of these metabolites to advance eco-friendly strategies for controlling root-knot nematodes and to develop resistant plant lines. Conclusion: Soil-streptomycete metabolites could be utilized in RNA interference to enhance tomato resistance to root-knot nematodes via de novo synthesis of protective small interfering and microRNAs, supporting agrobiological applications.

This study investigates the impact of chemical and biological treatments on the mycobiota of winter wheat seeds and the fungal composition of the soil. Conducted in 2023-2024 using the winter wheat variety Aliot, the research aimed to determine how different seed treatments affect the microbial...

Goal. To establish the peculiarities of infection of seeds and seedlings of cereals, legumes, oilseeds and cereals by a complex of FSSC species, to determine the factors influencing the spread of the pathogen. Methods. Laboratory methods: germination of crop seeds in different soil samples and study of seedling development; identification of fungal species that formed mycelium layers during seed germination; analysis of soil mycobiota; determination of drug efficacy. Results. In 2023—2024, the seeds of winter wheat, spring barley, winter rye, corn, sunflower, soybeans, beans, peas, millet, and buckwheat were studied for FSSC infection during germination in soil. Seeds were germinated in soils from different regions of Ukraine. The main symptoms of infection with the fungi of the F. solani species complex were studied. FSSC were isolated into pure culture to study their cultural and morphological characteristics. In order to find control of these phytopathogens, the factors influencing their spread were investigated: soil samples, precursor, crop genotype, seed treatment, and the use of various types of explosives. Conclusions. FSSCs cause the formation of fluffy white-pink mycelium layers and are often the reason why seeds do not germinate in the soil and necrosis forms on the seedlings. Differences in the color of colonies and sporulation structure were found when fungi were isolated from ungerminated seeds of different crops. The number of FSSC species was significantly influenced by the soil sample, precursor, crop genotype, seed treatment, and the effects of various weapons. The largest number of fungi was found during germination of rye seeds in sandy loam soil of Kyiv region, which explained the lowest germination rate of seeds in the compared soil samples. The study of soybean seed germination in soils from Poltava region revealed the best predecessor for this crop — corn, which proved to be the most resistant to the development of the F. solani species complex. It was shown that the bean variety Nautica was almost five times more resistant to FSSC than T9905. The efficiency of using a mixture of preparations (Merivon® Pro, KS; 0.3—0.4 l/t; Ekovital and Vitazim; 1 l/t) against Fusarium bacterial infection of soybean seeds was 46.3%. The consequences of the use of explosive weapons led to quantitative and qualitative changes in the mycobiota of the studied samples of chernozems from Sumy and Kharkiv regions.