The effect of a suspension of the strain Pseudomonas sp. GEOT18 under conditions of phosphate fertilizer application on the morphophysiological parameters and productivity of Hordeum vulgare

Background. Microbe-plant interactions are a well-known mechanism in science and practice for activating growth and increasing productivity in agricultural crops. The purpose of this study was to evaluate the effect of a suspension of the Pseudomonas sp. GEOT18 strain, applied with phosphate fertilizers, on the morphophysiological parameters and productivity of common barley (Hordeum vulgare L.). Materials and methods. The effect of the strain suspension on the growth and productivity of H. vulgare cultivar Sonet was studied through field trials in 2020 and 2022, and the strain's performance under additional phosphorus fertilizer application was assessed in 2023–2025. The strain suspension was applied twice: by seed bacterization before sowing and by spraying the phyllosphere during the tillering phase. Results. Long-term field experiments suggest that a suspension of the Pseudomonas sp. GEOT18 strain increases the assimilation surface, the content of photosynthetic pigments, and the accumulation of dry matter in aboveground organs, both alone and under conditions of additional phosphate nutrition. Grain productivity of H. vulgare variety Sonet in the Non-Chernozem zone of Russia in experimental variants exceeds the control by 16–39 % when applying a suspension of the strain and by 72–113 % when applying a suspension of the strain together with mineral fertilizers (by 5–12 % relative to variants with the application of the same doses of phosphate fertilizers, but without using a suspension of the strain). The effect of the Pseudomonas sp. GEOT18 suspension may be associated both with the ability of bacteria to synthesize IAA (7.87 ± 0.71 mg/l) and to release phosphorus from insoluble calcium phosphate into a form accessible to plants. Conclusions. The obtained results allow us to consider a suspension of the Pseudomonas sp. GEOT18 strain as a basis for the development of a biopreparation..