The general lack of knowledge on the conditions of Western Siberia (Omsk region) and the taxonomic diversity of zonal soils determines the relevance of these studies. The research was carried out in order to study the effect of complex biologics on the taxonomic diversity of the fungal component of the microbiome of the rhizosphere of cereals and the phytosanitary condition of crops in the southern forest-steppe (meadow-chernozem soil) and subtaiga (gray forest soil) zones of the Omsk Irtysh region (Western Siberia). This work was carried out in 2022–2023, using laboratory studies in combination with field experiments and metagenomic and statistical analyses. The objects of research were varieties of cereals and grain forage crops of Omsk selection: soil microorganisms. The scheme of the experiment involved the study of the following options: varieties of cereals (factor A): spring soft wheat—Omsk 42, Omsk 44, Tarskaya 12; durum wheat—Omsk coral; barley—Omsk 101; oats—Siberian hercules; bacterial preparation for seed inoculation (factor B) without the drug—Mizorin and Flavobacterin. The sampling of the plant rhizosphere for metagenomic analysis was carried out during the earing phase (July). For the first time, the taxonomic composition of the fungal community was determined based on the analysis of amplicon libraries of fragments of ribosomal operons of ITS2 fungi during colonization of crop roots by nitrogen-fixing bacteria in various soil and climatic zones of the Omsk region. The fungal component of the microbiome was analyzed in two zones of the Omsk region (southern forest-steppe and subtaiga). The five dominant phyla of soil fungi were located in the following decreasing series: Ascomycota (about 70%) > Mortierellomycota (about 7%) > Basidiomycota (about 5%) > Mucoromycota (3%) > Chytridiomycota (1%). The five main genera of fungi inhabiting the rhizosphere of cereals are located in a decreasing row: Giberella (6.9%) > Mortierella (6.6%) > Chaetomium (4.8%) > Cladosporium (3.8%) > Rhizopus (3.3%). The predominantly positive effect of biologics of associative nitrogen fixation on the fungal community of the soil (rhizosphere) of experimental sites located in different soil and climatic zones has been established. During seed bacterization, the growth of saprotrophic fungal genera was noted in relation to the control variants Pseudogymnoascus, Chloridium, Clonostachys, Trihoderma, etc., and the fungicidal properties of bacterial strains introduced into the soil were actively manifested relative to phytopathogenic fungi of the genera Alternaria, Blumeria, Fusarium, etc. According to the results of determining the number of infectious structures of Rhizoctonia solani, it was found that the population of the soil with viable cells of this pathogen was 1–3 pcs/g (below the threshold of harmfulness, PV 20 pcs/g of soil), which indicates a favorable phytosanitary situation with respect to the pathogen. The fungicidal effect of the applied bacterial fertilizers on Rhizoctonia solani could not be detected. The number of Bipolaris sorokiniana varied depending on the drug used. In the conditions of the southern forest-steppe zone of the Omsk region (meadow-chernozem soil), the greatest fungicidal effect was noted in Flavobacterin application variants on wheat of the Omsk 42 variety, durum wheat of the Omsk coral variety, and barley; the decrease in conidia relative to the control was 73, 35, and 29%, respectively. In the subtaiga zone of the Omsk Irtysh region (gray forest soil), as in the southern forest-steppe zone, pre-sowing bacterization of seeds with Flavobacterin led to a decrease in Bipolaris sorokiniana in the rhizosphere of wheat of the Omsk 42 variety by 18%, and oats by 27%, to control. The use of the drug Mizorin in some variants of the experiment led to an insignificant decrease in the harmful fungus or had no effect at all.

Crop infection is a stress factor for plants. The development and spread of fungal phytopathogens (Fusarium, Bipolaris, Alternaria, etc.) of the root system leads to a significant decrease in both quantitative, and qualitative parameters of grain crop productivity. The current paper has presented the data (2011–2018) on the study of subsoil parts of spring wheat plants when they are damaged by root rots of various etiologies, depending on the forecrops, agricultural technology and plant protection products. In the conditions of the Omsk region, the introduction of rapeseed into field crop rotations is justified. The grain crop has a positive effect on improving the phytosanitary condition of the soil and crops. There has been established that the greatest spread of infection on the root system of plants is identified on wheat sown in fallow (35–46 %), the minimum spread after rapeseed (7–16 %). Seeds of bluegrass weeds during protective tillage are concentrated in an uppermost (0–10 cm) soil layer. The increased weed infestation of agrophytocenosis reduces the competitiveness of cultivated plants and, as a result, the population of B. sorokiniana conidia in soil increases, creating unfavorable conditions for spring wheat development, especially during the initial period of growth. The highest crop productivity, regardless of a forecrop, mean for intensification options, was provided by moldboard tillage with 3.02 t/ha (wheat sown in fallow); 2.60 t/ha (wheat sown after wheat) and 2.15 t/ha (wheat sown\ after rapeseed). With a protective tillage, there was grain productivity decrease on 0.20 t/ha (wheat sown in fallow); 0.22 t/ha (wheat sown after wheat) and 0.12 t/ha (wheat sown after rapeseed) t/ha, respectively, in comparison with a moldboard technology. When fertilizing and herbicidal-fungicidal treatment of sowings during a vegetation period of plants, there is a slight difference between agricultural technologies. The complex use of chemicals reduces the infection of agrophytocenosis on 7–11 % and increases spring wheat productivity upto 4.14 t/ha (on 98 %) relative to extensive agricultural technology.

The general lack of knowledge in the conditions of Western Siberia (Omsk region), the nitrogen fixation process and quantitative data on its activity in agroecosystems do not allow us to establish the true role of nitrogen fixing microorganisms in the nitrogen balance of soils and plant nutrition, to estimate the proportion of biological nitrogen (due to associative nitrogen fixation). The relevance of the research lies in the biological assessment of the reception of inoculation of agricultural seeds with biological preparations of fungicidal-stimulating action of Russian production (ARRIAM, Pushkin). The research were study the infiuence of biological products of associative diazotrophs on the activity of the associative nitrogen fixation process in the rhizosphere of cereals, the survivability of introduced bacteria, and crop productivity in the conditions of the southern forest-steppe abd subtaiga of Western Siberia. The work was carried out in field experiments on varieties of Omsk breeding of spring wheat Omsk 42, Omsk 44, Tarskaya 12, Omsk Coral, barley Omsk 101, oats Siberian Hercules. Pre-sowing bacterization of seeds was carried out with an inoculant of diazotrophic bacteria of the genus Arthrobacter mysorens 7 and an inoculant of fungicidal-stimulating bacteria of the genus Flavobacterium sp. L-30. Rhizosphere sampling was leaded out in tillering (June), earing (July), grain filling (August). The activity of the associative nitrogen fixation process in the rhizosphere of cereals varied significantly depending on the use of biological products, the type of crop and the zone of their cultivation. Under the cultivation of cereals during the growing seasons with the introduction of Flavobacterium sp. bacteria. and Arthrobacter mysorens 7, an increase in nitrogen-fixing activity in the rhizosphere and dinamic survivability of introduced bacteria were found. On gray forest soil, for all crops of the experiment, the absolute sizes of nitrogen fixation were lower than on meadow-chernozem soil. In the conditions of the southern forest-steppe zone, the highest level of nitrogen-fixing activity was in the rhizosphere of soft wheat variety Omsk 42 and durum wheat Omsk Coral variety, amounting to 150.7-322.0 and 140.0-393.0 nM C2H2/100 g of soil with the introduction of bacteria of the genus Arthrobacter mysorens 7, 149.0-281.0 and 86.2-554.5 nM C2H2/100 g of soil with introduction of Flavobacterium sp. accordingly. In parallel, an increase in the number of CFU introduced bacteria was observed, as a result of which the nitrogen fixation process was activated. In the subtaiga zone of the Omsk region, the largest sizes of associative nitrogen fixation were found in the rhizosphere of soft wheat varieties Omsk 44 and Tarskaya 12, amounting to 46.3-230.7 and 24.0-130.0 nM C2H2/100 g of soil with the introduction of bacteria of the genus Arthrobacter mysorens 7, 62.0-208.3 and 52.0-178.7 nM C2H2/100 g of soil with the introduction of Flavobacterium sp. accordingly. Simultaneously with the increase in the size of nitrogen fixation, the number of bacterial cells of diazotrophs of the genus Arthrobacter mysorens 7 in the rhizosphere of these wheat varieties was also significant, during the growing season it varied between 1.28-5.23 × 106 CFU/g and 0.28-7.45 × 106 CFU/g. Barley was isolated from grain crops, the activity of the process in the rhizosphere of this crop was up to 164.3 nM C2H2/100 g of soil when Flavobacterin was used. A statistically significant (p<0.05) positive correlation between the process of associative nitrogen fixation and the yield of agricultural crops was revealed, in the southern forest-steppe zone r=0.927, r=0.986, r=0.897 (Omsk wheat 42, Omsk Coral, Siberian oats Hercules), in the subtaiga zone r=0.998, r=0.991, r=0.916, r=0.990 (Omsk wheat 42, Omsk 44, Omsk barley 101). EDN: NILFDX

Soil microflora is a powerful indicator of the condition of arable soils. This review summarizes the latest scientific reports concerning the structure of the microbial cenosis of meadow-chernozemic soil under agrogenic effects, as well as demonstrate its own results. The research was carried out on spring soft wheat in field experiments of the Omsk Agricultural Scientific Center in the southern forest-steppe of Western Siberia in order to determine the effect of the use of biological products of associative diazotrophs on the biological (ecological) properties of the rhizosphere of spring soft wheat and to determine their relationship with crop yield. In this research we found out that the root microbiome of soft wheat reacted ambiguously to inoculation of biological products and depended both on the genotypic characteristics of the varieties and on the preparations used. The number of copiotrophs, oligonitrophils and microfungis increased in the rhizosphere of spring soft wheat of the Omsk 44 variety when using the bacterial fertilizer Flavobacterin. The Omskaya 44 variety also stood out with the largest total number of microflora, the use of the Flavobacterin biopreparation stimulated its growth relative to the control by 22%. The use of Mizorin did not significantly affect the activity of root microorganisms. The microbial population of wheat varieties Omskaya 42 and Tarskaya 12 did not respond to the introduction of bacteria of the genus Arthrobacter mysorens 7 and Flavobacterium sp. L-30. Immobilization processes prevailed in the rhizosphere of the studied varieties, to the greatest extent in wheat Tarskaya 12 and Omskaya 44. The activity of hydrolytic enzymes in most variants of the experiment tended to increase relative to the control (up to 17%), however, the activity of the redox enzyme catalase decreased from the applied agricultural method within the experimental error (up to 4%). A statistically significant (p<0.05) positive (r=0.675) dependence of wheat yield on the amount of microflora in the rhizosphere was revealed.

Background. Analyzing photosynthetic processes in a plant makes it possible to opine on the rate of its growth and development. In addition to classical physiological techniques, an interest is currently growing in spectrometry, which provides a realtime opportunity, based in the values of vegetation indices, to find out whether a plant is under stress or not.Materials and methods. Spring bread wheat cvs. ‘Omskaya 42’, ‘Omskaya 44’, and ‘Tarskaya 12’, and spring durum wheat cv. ‘Omsky Korall’ were analyzed in Western Siberia. Seeds were bacterized before sowing with an inoculant of diazotrophs belonging to Arthrobacter mysorens 7 and Flavobacterium sp.Results. Identification of increased plant growth and development rates is possible with the following vegetation indices in the ear emergence phase: TCARI = 27.32, MCARI = 106.4, SPAD = 40.6, CPHLT = 25.02, CPHLB = 14.5, CPHLA = 8.46, and CCI = 27.5, and those in the grain filling phase: CPHLT = 10.4, CPHLB = 7.2, and CPHLA = 4.7. The highest nitrogen-fixing activity level was observed in the rhizosphere of bread wheat cv. ‘Omskaya 42’ and durum wheat cv. ‘Omsky Korall’, amounting to 150.7–322.0 and 140.0–393.0 nM C₂H₄/100 g of soil, respectively, with the introduction of Arthrobacter mysorens 7 bacteria, and 149.0–281.0 and 86.2–554.5 nM C₂H₄/100 g of soil, respectively, with Flavobacterium sp.Conclusion. Consistently high values of the associative nitrogen fixation process were recorded in the variants involving bacterization of wheat seeds of cvs. ‘Omskaya 42’ and ‘Omsky Korall’ with the stimulating fungicide drugs Mizorin and Flavobacterin. According to the values of the TCARI and SPAD indices, it is possible to opine on the potential nitrogen-fixing activity and the yield of a cultivar.