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Current approaches to land use and agricultural production are increasingly aimed at achieving high productivity through the use of crop rotation, siderites, integrated plant protection, minimized soil cultivation, microbiological fertilizers, and biological preparations. Modern microbiological preparations enhance the uptake of nitrogen and ash elements by plants, improving the rhizosphere of plants and the quality of strawberry fruit. Aim. To establish the effect of Extrasol applied using drip irrigation and various forms of mineral nitrogen fertilizers on the chemical composition of leaves and fruit of garden strawberry.Materials and methods. Garden strawberry plants of the Rusich and Troitskaya cultivars were treated with Extrasol and mineral fertilizers. Experiments were carried out in 2017–2020 at open-ground plots of the Federal Horticultural Center for Breeding, Agrotechnology and Nursery (Moscow Oblast). The experimental plots were characterized by soddy podzolic soils of medium-loam granulometric composition. Plant samples were analyzed using conventional methods. The experimental scheme consisted in the application of various nitrogen fertilizers (ammonium nitrate, urea, and ammonium sulfate) either in combination (2 mL/L of the working solution) or without Extrasol. Conclusions. In strawberry cv. Rusich, the use of ammonium nitrate increased the calcium content in plant leaves and decreased its content in fruit, which negatively affected the crop quality. Mineral fertilizers applied in combination with Extrasol increased the nitrogen content in leaves and fruit. The combined use of the amide form of nitrogen (urea) and Extrasol adversely affected the level of nitrates in cv. Troitskaya fruit. The use of fertigation and Extrasol reduced the amount of soluble dry substances in strawberry fruit.

The article highlights current research that discusses the importance, role and application potential of endophytic bacteria in industrial horticulture. A review of national and foreign publications on the prevalence, taxonomic composition and function of endophytic bacteria in agricultural and horticultural plant objects is presented. Key endophytic bacterial phyla and genera associated with agricultural plants have been previously characterised. The authors consider the main plant organs and tissues that harbour endophytic bacteria, routes of bacterial colonisation and host-to-host transmission, endophyte relationships with the host species, as well as the genotype, seasonal period, environment, taxonomic and varietal composition of host plants. The host-microbiome relationship is intimate and mutually beneficial. Endophytic bacteria positively impact organogenesis and embryogenesis in agricultural plants, transforming phosphorus and atmospheric nitrogen into plant-absorbable forms and producing hormones that stimulate plant growth. Endophytic flora are able to produce vitamins, siderophores, phytohormones, antibiotic like-substances and phytopathogen-antagonistic exoenzymes, which play a role in enhancing a plant’s resistance to disease and stress, while simultaneously increasing its yield. Current evidence indicates the ability of endophytic bacteria isolated from garden crops to produce indolyl acetic acid, solubilise phosphates, potentially stimulate plant growth and suppress antagonistic phytopathogens. Endophytic bacteria are important regulators of growth, development and fruiting in garden crops, sustaining their reproduction and thus having a strong potential for use in biopreparations in industrial horticulture.

The microbiome of cultivated and wild potato species was studied, effective endophytic bacteria were isolated, and experimental samples of microbial preparations were developed. The effectiveness of microbial preparations based on Bacillus thuringiensis W65 and Paenibacillus xylanexedens N40 strains in the Leningrad and Novosibirsk regions on new potato varieties is shown.

Chickpea (Cicer arietinum L.), a valuable legume crop, is an essential component of diet in many Asian, African, European and American countries. A major role in increasing its adaptive potential, quality and quantity of the yield is played by symbiotic and associative bacteria. The main aim of this research was to study the effect of combined pre-seed treatment with microbial inoculants and Mo nanoparticles on the composition of root exudates and the taxonomic diversity of microorganisms in the chickpea plants rhizosphere. We studied seed germination, the activity of enzymes involved in antioxidant protection system and the formation of plant-microbial system under the influence of nodule and rhizosphere bacteria and molybdenum (Mo) nanoparticles introduced into seeds before sowing. Rhizosphere microbiome was studied with the help of pyrosequencing method. Maximum numbers of introduced bacteria were observed in variants with Mo nanoparticles. The symbiotic effectiveness of Mesorhizobium ciceri strain ST282 was further improved by co-inoculation with “helper bacteria” Bacillus subtilis and Mo nanoparticles. Effective symbiosis was shown to be an important factor determining the formation of the rhizosphere microbiome by the representatives of the order Rhizobiales and influencing the numbers and the composition of the rhizosphere microbial community. A self-sufficient legume-rhizobium symbiosis improved the physiological status of the plant, increasing structural diversity of the microbial community of the rhizosphere through changes in the activity of root exudates, and paved the way for the development of the most effective associative bacteria.

The literature review focuses on endophytic bacteria inhabiting woody plants. Endophytic bacteria for genera Pseudomonas, Bacillus, Paenibacillus, Burkholderia, and Erwina are shown to be found in almost all woody tissues. In additional, endophytic bacteria have been found in reproductive plant organs. It is shown that endophytic bacteria have functional properties that are useful for host plants: the ability to fix atmospheric nitrogen, produce growth simulating and biocontrol substances, and to induce systemic resistane of plants to biotic and abiotic stresses. Endophytic bacteria are a major part of the microbiome of woody plants, possess valuable functional properties of host plants, and are a promising biotechnological resource for the development of complex microbial preparations for agriculture and forestry.

Sphagnum mosses serve as a unique habitat for microorganisms, which play an important role both for the host plants and the peatland ecosystems. The aim of the present study was to isolate endophytic bacteria from the tissues of Sphagnum mosses and to screen them for strains promising for further application in agricultural microbiology. About 50 samples of Sphagnum fallax (H. Klinggr.) H. Klinggr. and Sphagnum magellanicum Brid. were collected in the Austrian Alps and the Lenindgrad Region of Russia in 2009–2010. Endophytic bacteria were detected inside the moss plants using fluorescent in situ hybridization (FISH) followed by confocal laser scanning microscopy (CLSM). Altogether, 283 isolates were obtained by cultivation on the nutrient media. Examination of the isolates for the antagonistic activity revealed that more than 50% of them could suppress the growth of phytopathogenic and toxigenic fungi. More than 30% of isolates showed some antagonistic activity against microbial phytopathogens. The isolated strains could colonize crops and promote their growth. Molecular-genetic identification coupled with physiological/biochemical characterization showed that the dominant endophytic groups belonged to the genera Burkholderia, Pseudomonas, Flavobacterium, Serratia and Collimonas. The isolated endophytes were shown to be promising objects for the development of effective growth-promoting and protective microbiological preparations to be used in agriculture.

Bacillus subtilis Ch-13 industrial strain was shown to have a wide spectrum of antagonistic activities against different species of phytopathogenic fungi and bacteria. The B. subtilis Ch-13 strain produces lytic enzymes; cyanide and other antifungal metabolites; stimulates plant growth, producing phytohormones—auxin derivatives. This strain by 2.5 times reduced the quantity of tomato plants infected with phytopathogenic fungus Fusarium oxysporum during inoculation. Fungi abundance on roots with bacterial inoculation was 6.9 times less than in the absence of inoculation. The application of detected antifungal metabolites as biochemical markers for the strain enables to control the stability of physiologic and biochemical characteristics of the producer, and ensures a rapid quality assay of biopreparations with high performance liquid chromatography (HPLC).

The development of Fusarium culmorum and Pseudomonas fluorescens in soil, and the relations between them, were studied using membrane filters containing the fungus, the bacterium, or both microorganisms; the filters were incubated in soil. F. culmorum was identified by indirect immunofluorescence: the GUS-labeled strain was used to visualize P. fluorescens. It was found that F. culmorum introduced in soil can develop as a saprotroph, with the formation of mycelium, macroconidia, and a small amount of chlamydospores. Introduction of glucose and cellulose resulted in increased density of the F. culmorum mycelium and macroconidia. P. fluorescens suppressed development of F. culmorum mycelium in soil but stimulated formation of fungal chlamydospores. Decreased mycelial density in the presence of P. fluorescens was more pronounced in unsupplemented soil and less pronounced when glucose or cellulose was intiodaced. F. culmorum had no significant effect on P. fluorescens growth in soil.

In this review data on the possibility of using endophytic bacteria for improving crop yields and quality are discussed.

Bacillus subtilis Ch-13 industrial strain was shown to have a wide spectrum of antagonistic activities against different species of phytopathogenic fungi and bacteria. The B. subtilis Ch-13 strain produces lytic enzymes; cyanide and other antifungal metabolites; stimulates plant growth, producing phytohormones-auxin derivatives. This strain by 2.5 times reduced the quantity of tomato plants infected with phytopathogenic fungus Fusarium oxysporum during inoculation. Fungi abundance on roots with bacterial inoculation was 6.9 times less than in the absence of inoculation. The application of detected antifungal metabolites as biochemical markers for the strain enables to control the stability of physiologic and biochemical characteristics of the producer, and ensures a rapid quality assay of biopreparations with high performance liquid chromatography (HPLC).

The striking increase in the use of nitrogen (N) and phosphorus (P) fertilizers between 1960 and 2000 by intensive agricultural practices has led to degradation of air and water quality (Tilman et al., 2001). However, the existence of common legume plant genes that are implicated in both nitrogen-fixing and arbuscular mycorrhizal symbioses – the two associations that improve mineral nutrition, water supply and tolerance to biotic and abiotic stresses of plants – poses the question of how such a tripartite symbiosis (legume plant + arbuscular mycorrhizal fungi + nodule bacteria) can be exploited in sustainable agriculture (Borisov et al., 2004). The great genetic variability shown in the effectiveness of such a system for pea (and, obviously, for other legumes) clearly demonstrates that we can and should breed legumes to increase the symbiotic potential of the tripartite symbioses (Jacobi et al., 2000).

The development of Fusarium culmorum and Pseudomonas fluorescens in soil, and the relations between them, were studied using membrane filters containing the fungus, the bacterium, or both microorganisms; the filters were incubated in soil. F. culmorum was identified by indirect immunofluorescence: the GUS-labeled strain was used to visualize P. fluorescens. It was found that F. culmorum introduced in soil can develop as a saprotroph, with the formation of mycelium, macroconidia, and a small amount of chlamydospores. Introduction of glucose and cellulose resulted in increased density of the F. culmorum mycelium and macroconidia. P. fluorescens suppressed development of F. culmorum mycelium in soil but stimulated formation of fungal chlamydospores. Decreased mycelial density in the presence of P. fluorescens was more pronounced in unsupplemented soil and less pronounced when glucose or cellulose was intiodaced. F. culmorum had no significant effect on P. fluorescens growth in soil.

732 ACKNOWLEGMENTS should read as follows: This work (sections “Biodiversity of endophytic bacteria, artificial inoculation of plants with endophytic bacteria and colonization of plant endosphere, influence of bacterial endophytes on plant growth and development, the ability of endophytic bacteria to control the development of plant diseases (“biocontrol activity”), endophytic bacteria – producers of “secondary metabo lites”) was supported by the Russian Science Foundation (project no. 14 16 00146), section “Prospects for the use of endophytic bacteria in microbial preparations that improve plant growth” with the financial support of the leading universities of the Russian Federation (grant 074 U01)”. ERRATA

Flavocin, an agent with fungistatic and bacteriostatic activities, was isolated from the culture of Flavobacterium sp. L-30. The data on the physico-chemical and biological properties of flavocin A, the major active component, are presented. The component was identified with metabolites of the genus Flavobacterium and other genera of nonsporulating bacteria. Flavocin was highly efficient in the treatment of various farm crops. The antagonistic effect of flavocin was observed under field conditions in growing sugar beet, barley, spring wheat, potato and grape. Presowing and nonradical exposure to flavocin lowered the affection of the plants with brown patch, scab, soft rot and oidium.

It was created the collection of the associative nitrogen-fixing bacteria from genera Aquaspirilium, Azospirillum, Rhodospirillum, Arthrobacter, Flavobacterium, Bacillus, isolated from rhizoplane of grain and fodder cereals, new fodder crops from families of Apiaceae, Brassicaceae, Asteraceae.

In this review data on the possibility of using endophytic bacteria for improving crop yields and quality are discussed.