The dissertation is dedicated to the study of rhizosphere microbial communities and symbiosis when the seeds were inoculated microbial bioformulation and fungicides application.
In the microbiome of dark gray podzolic soil of soybean rhizosphere by molecular ecology methods 21 phylums, 63 classes, 111 orders, 271 species of bacteria, and 2 phylums, 2 classes of archaea were revealed. Analysis of the taxonomic structure of the microbiome at the level of phylum showed that bacteria were the absolute dominants, archaea were 0,5-4,5%. Among the identified bacterial phylums, three were dominant: Acidobacteria, Actinobacteria and Proteobacteria.
Sequences that were not previously described as representatives of the soybean rhizosphere microbiome were identified for the first time – representatives of phylums: Chlorobi – green sulfur bacteria; free-living Elusimicrobia, characterized by the presence of a new group of nitrogenase paralogs; Chlamydiae, intracellular parasites of eukaryotes and amoeba; archaea Parvarchaeota and Crenarchaeota, and also uncultivated forms of Gracilibacteria and FBP. Soybean microbiome rhizosphere studies at class level identified 63 taxonomic units, of which Actinobacteria and Alphaproteobacteria were dominant and 21 classes were subdominant, including members of the photosynthetic Chloracidobacteria and archaea Thaumarchaeota, which are rarely found in the rhizosphere. It was found that when the seeds were treated with Ecovital and fungicides, in comparison with untreated control, quantitative changes took place in the microbiome: the representation of subdominant phylums Firmicutes, Gemmatimonadetes and Bacteroidetes increased, while the number of archaea Crenarchaeota decreased. It was shown that among of the class Bacilli the genus Bacillus was the most represented. When the seeds were inoculated with the bioformulation Ecovital, which includes phosphate-mobilizing bacilli, the representation of bacteria of the genus Bacillus in the rhizosphere microbiome increased. This may indicate that the introduced bacilli genera of the Rhizobiales order were determined. For the first time, representatives of the genera Microvirga and Bosea were identified. Previously, they were not described in the soybean rhizosphere. Representatives of these genera belong to the group of new symbiotrophs forming nodules and fixing nitrogen. The identification of these bacteria expands the search area for new strains to activate soybean-rhizobial symbiosis and increase its effectiveness.
For the first time, an increase in the biodiversity of the soybean rhizosphere microbiome was shown when using microbial inoculation and application of fungicides Kinto duo or Maxim Star, which was confirmed by increase of Shannon and Menchinic indices (species richess), also decrease of Simpson and Berger-Parker indices (dominance species). It was shown that under using of different seed treatment schemes in the root zone microbiome at the level of large taxa, quantitative changes occur in the composition of phylum and classes, and at the level of minor components, such as families and genera, qualitative changes were observed.
It was established that all strains of rhizobia used as inoculants stimulated the development of nitrogen-fixing microorganisms in the rhizosphere. Fungicides Maxim Star and Vitavax 200 FF, used separately without inoculation, inhibited the development of microorganisms in almost all studied groups by 1,5-4,5 times. The negative effect of fungicides on the quantity of microorganisms in most cases when combined with various strains of rhizobia was leveled. Nitrogenase activity under use of the fungicide Kinto duo with strains B-6035, B-6023 or remained at the level of variants with inoculation, or increased by 2 times. Vitavax 200 FF fungicide suppressed the nitrogen-fixing activity of the studied strains in symbiosis. It was established that the nitrogen-fixing activity increased in the bean-rhizobial system after inoculation with Ecovital and in combination with Vitavax 200 FF. Pre-sowing treatment with Maxim Star and Kinto duo fungicides inhibited the nitrogenase activity of rhizobia. It was observed the significant inhibition of the development of target objects – pathogens of ascochitosis and septoriosis in all experimental variants with the combined use of fungicides and bacterization. The positive effect of the joint use of Ecovital and fungicides on the photosynthetic apparatus of soybeans was established: the content of chlorophylls a and b in the leaves increased. The combined use of fungicides and a complex microbial bioformulation Ecovital contributed to an increase in the productivity of soybeans.
As a result of the research, the scientific background of the ecologically friendly combined use of microbial bioformulations and fungicides have been developed to preserve the biodiversity of soil microbiota, improve the phytosanitary condition of agrocenoses and increase plant productivity.
