Abstract
Using a nitrogen-free media, 232 bacteria were isolated from 50 soil samples collected in the provinces East Azerbaijan, Gilan and Ardabil in North of Iran. Plant growth-promoting traits of selected isolates were assessed under in vitro conditions. Moreover, PCR–RFLP analysis of the 16S rDNA and nifH genes was applied to investigate their genetic diversity. Forty percent of the bacteria were able to produce siderophores and the isolate 36A-2 (Pseudomonas) was identified as the best siderophore producer. All bacteria showed a much better phosphate solubilizing capacity with tricalcium phosphate than with rock phosphate as the phosphate source. The bacterial isolate 23A-6 (Pseudomonas) was observed to be the best phosphate solubilizers in the presence of tricalcium phosphate and 34SPIII (Pseudomonas) in the presence of rock phosphate. A K releasing capacity was shown for the bacterial isolates 36A-2 (Pseudomonas), 44SP-2 (Azotobacter chroococcum), 14SPIII (Achromobacter), 14SP2-1 (Azotobacter chroococcum) and 14A-4 (Agrobacterium). However, for most of the bacteria no K releasing ability was observed. The best IAA producer in the presence of 100 mg L−1 L-tryptophan (12.26 mg L−1) was found to be the bacterial isolate 23A-6 (Pseudomonas). Molecular and biochemical identification revealed that the isolates included in the study belong to the genera Azotobacter, Beijerinckia, Klebsiella, Pseudomonas, Rhizobium, Agrobacterium, Achromobacter, Stenotrophomonas and Sphingomonas. The Azotobacteria included in the study were all identified as A. chroococcum. With the exception of the isolate 35A-2, all of them produced the same PCR–RFLP pattern with the 16S rDNA and nifH PCR products. The bacterial isolates 23A-6, 34SPIII and 36A-2 (Pseudomonas) were identified as promising candidates to be used as plant growth-promoting bacteria.
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Acknowledgements
This study was carried out at the University of Tabriz. The authors would like to thank the Iranian National Science Foundation, the University of Tabriz and the Bu-Ali Sina University of Hamedan for providing the facilities and the financial support.
Funding
Partial financial support was received from Iranian National Science Foundation (INSF). The authors would like to thank the INSF, the University of Tabriz and the Bu-Ali Sina University of Hamedan for providing the facilities and the financial support.
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All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Mitra Ebrahimi, Ali Akbar Safari Sinegani, Mohammad Reza Sarikhani, Seyed Abolghasem Mohammadi, Nasser Aliasgharzad and Ralf Greiner. The first draft of the manuscript was written by Mitra Ebrahimi and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. The authors approve that the manuscript is original work and has been solely submitted to this journal. Moreover, all authors are sure that all data and materials as well as software application or custom code support their published claims and comply with field standards.
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Ebrahimi, M., Sinegani, A.A.S., Sarikhani, M.R. et al. Plant Growth-Promoting Traits and Genetic Diversity of Free-Living Nitrogen-Fixing Bacteria Isolated from Soils in North of Iran. Iran J Sci Technol Trans Sci 46, 761–769 (2022). https://doi.org/10.1007/s40995-022-01291-9
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DOI: https://doi.org/10.1007/s40995-022-01291-9