Abstract. The use of biofertilizers based on plant growth promoting (PGP) bacteria is a promising direction in agri-biotechnology. The purpose was to evaluate the PGP-attributes of Bacillus sp. and to reveal the morphophysiological features of rapeseed (Brassica napus L.) when inoculated with these rhizobacteria. Methods. The ability of Bacillus sp. strain TO15c isolated from the rhizosphere of Taraxacum officinale on Zack's nitrogen-free medium to produce indol-3-acetic acid (IAA) and phosphates was studied. In pot-scale experiments, the assessment of changes in the morphophysiological characteristics of rapeseed upon inoculation with rhizobacteria both in the absence and in the presence of nitrogen fertilizer was performed. At the end of 100-day vegetation, shoot length, total leaf area, fresh biomass, content of macronutrients and photosynthetic pigments were determined. Results. The ability of TO15c to produce IAA (up to 26 mg/L) and solubilize phosphate (up to 60 mg/L) has been proven. Soil inoculation with rhizobacteria in the presence of ammonium nitrate led to the increase in shoot length by 24 % and total leaf area by 16 %. The aboveground fresh biomass increased by 1.5 times, the underground by 2.5 times, and the content of macronutrients improved. The rise in the photosynthetic pigment content (1.5 times on average) was also noted when inoculated with TO15c. The maximum effect was achieved with the rhizobacteria and nitrogen fertilizer combined application. Scientific novelty. The effectiveness of Bacillus sp. TO15c on rapeseed increased in the presence of nitrogen fertilizer, despite the fact that these PGPR were able to fix atmospheric nitrogen.
Brassica napus, bacterial biofertilizer, plant-microbial interactions, indol-3-acetic acid, phosphate solubilization, macronutrients, photosynthetic pigments
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