Screening of soil-rhizosphere microorganisms promising for the control of phytopathogens and stimulation of plant growth

In the context of agriculture ecologization, the importance of searching for microorganisms with antagonistic activity against phytopathogens and properties related to the stimulation of plant growth is increasing. The purpose of this work is the selection of promising microbial isolates for further use as part of agricultural biopreparations. The study examined 24 bacterial isolates obtained from soil and rhizosphere samples collected in meadow ecosystems and agricultural agrocenoses of various regions of the Russian Federation. The taxonomic affiliation of the bacterial isolates was determined using 16S rRNA gene sequences. Antifungal activity was evaluated against Fusarium oxysporum, Rhizoctonia solani, Alternaria alternata, and Bipolaris sorokiniana. Additionally, amylolytic, proteolytic, and phosphate-mobilizing activities were determined as an indicator of hydrolytic potential and specific traits associated with growth-stimulating effects. As a result of molecular-genetic identification, it has been established that the studied isolates primarily belong to the genera Bacillus, Pseudomonas, Priestia, Achromobacter, Enterobacter, Serratia, Enterococcus, and the Bacillaceae family. The highest overall antifungal activity was demonstrated by isolate 26, classified as Bacillus sp. (subtilis species complex), which inhibited all the studied phytopathogenic fungi. The maximum proteolytic activity was observed in isolate 35 (Pseudomonas sp., P. fluorescens group) and amounted to 2.45 cm, amylolytic activity in isolate 42 (Bacillaceae family) was 3.56 cm, and phosphate-mobilizing activity in isolate 39 (Bacillus sp., subtilis species complex) was 1.4 cm. It has been found that the isolates most promising in terms of the set of studied traits belonged predominantly to the genera Bacillus and Pseudomonas. The results obtained indicate the feasibility of further investigating these isolates as potential components of microbial consortia and biological preparations with biocontrol and growth-stimulating potential.

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