Bacteria associated with grapevine (Vitis vinifera L.) rhizosphere and their efficacy in plant growth promotion

Plant growth, development, and stress resistance depend on the presence of plant growth-promoting rhizobacteria (PGPR) in its rhizosphere. The detection of the highly active PGPR is of high importance due to their possible application as microbial inoculants for plant growth promotion (PGP) in agriculture. In this study, we report on PGPR from the rhizosphere of grapevine (Vitis vinifera L.) growing in Uzbekistan, as it was not studied before. Based on the screening of 37 isolates from grapevine rhizosphere for stimulation of wheat seed germination, just two isolates, BDI-1 and BDI-2 were chosen as the most active. In laboratory conditions, the isolates BDI-1 and BDI-2 increased wheat root length up to 1.48 and 1.5 times and shoot length up to 1.59 and 1.64 times, respectively, as compared to the control. Based on 16S rRNA gene analysis and comparison with the relative strains registered in GenBank of the National Center for Biotechnology Information (NCBI), the isolates BDI-1 and BDI-2 were identified as Pantoea agglomerans and Priestia megaterium, accordingly. Their 16S rRNA gene nucleotide sequences were deposited to GenBank under the accession numbers OP727725 for BDI-1 and OP782582 for BDI-2. Both isolates were phenotypically characterized and demonstrated phosphate-solubilizing and nitrogen-fixing abilities, producing indole-3-acetic acid (IAA) in a high amount; however, BDI-1 also produced siderophores and BDI-2 - 1-aminocyclopropane-1-carboxylate (ACC) - deaminase. Due to these features, the bacteria showed their high activity in the promotion of plant growth and seed germination. In conclusion, according to our results, P. agglomerans BDI-1 and P. megaterium BDI-2 are promising PGPR, which can be applied as microbial inoculants for plant growth improvement.