The Quality and Productivity of Strawberry (Fragaria x ananassa Duch.) Improved by the Inoculation of PGPR Bacillus velezensis BS89 in Field Experiments

Efficient plant-growth-promoting rhizobacteria (PGPR) used as biofertilizers and biological control agents are promising substitutes for minimizing the application of synthetic agrochemicals in crop production. We studied the effect of PGPR strain Bacillus velezensis BS89 alone and in combination with three forms of nitrogen fertilizers (ammonium nitrate, carbamide, and ammonium sulfate) on the productivity of two strawberry varieties in three-year field experiments. We first showed that the application of PGPR Bacillus velezensis BS89 on strawberries demonstrated the same effect as the application of nitrogen fertilizers. Use of the strain BS89 increased the chlorophyll content in plant leaves by 2.7-6.8%, and also increased the yield of berries by 6.7-36.4% for cv. Rusich and 7.5-19.3% for cv. Troitskaya depending on the form of nitrogen fertilizer. The best results in the yield of strawberry plants of the cv. Rusich were achieved in the variant BS89 + ammonium nitrate (41.9-57.4%), and the cv. Troitskaya-in the BS89 + carbamide variant (8.1-38.8%). Three-year use of strain BS89 for cv. Rusich resulted in an increase of runner's weight by 212.1%, and also the weight of the roots by 120%, thereby significantly improving the mineral nutrition of plants. This is mainly associated with the plant growth-promoting activity of Bacillus velezensis BS89, which was able to produce a high amount of IAA-494.1 mu g/mL. We believe that the PGPR strain BS89 can be successfully used for growing strawberries. However, each variety requires careful selection of the composition of nitrogen fertilizers and analysis of the compatibility of fertilizers and the PGPR strain.