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Plant Growth-Promoting Bacteria from Tropical Soils: In Vitro Assessment of Functional Traits
Juliana F Nunes1, Maura S R A da Silva1, Natally F R de Oliveira1
1Department of Soils, Institute of Agronomy, Federal Rural University of Rio de Janeiro, BR 465 Km07, Seropedica Rio de Janeiro 23897-000, Brazil.
Microorganisms
|October 29, 2025
Summary
This study screened 30 bacterial isolates for plant growth-promoting traits in tropical soils. Promising candidates like Pseudomonas azotoformans K22 were identified for developing sustainable agricultural solutions.
Area of Science:
- Agricultural Microbiology
- Soil Science
- Plant Pathology
Background:
- Sustainable agriculture in low-fertility tropical soils requires effective crop enhancement strategies.
- Plant growth-promoting bacteria (PGPBs) are a viable alternative to chemical inputs for improving crop productivity.
- Characterizing PGPB traits is crucial for developing effective microbial inoculants.
Purpose of the Study:
- To screen and characterize 30 bacterial isolates for multiple plant growth-promoting traits.
- To identify superior bacterial strains with potential for enhancing crop growth in tropical soils.
- To evaluate the potential of PGPBs for phosphate solubilization, potassium release, siderophore production, IAA synthesis, ACC deaminase activity, and antifungal properties.
Main Methods:
- In vitro screening of 30 bacterial isolates for key plant growth-promoting traits.
- Assessing phosphate solubilization from aluminum phosphate (AlPO4) and thermophosphate.
- Quantifying potassium release from phonolite rock, siderophore production, indole-3-acetic acid (IAA) synthesis, and ACC deaminase activity.
- Evaluating antagonism against Fusarium spp. and calculating a composite performance index.
Main Results:
- Significant variations (p < 0.05) in plant growth-promoting traits were observed among isolates.
- Efficient phosphate solubilization (up to 45.2 mg L-1) and potassium release (up to 23.5 mg L-1) were recorded.
- Pseudomonas azotoformans K22 exhibited high AlPO4 solubilization (16.6 mg L-1), and IAA production varied widely (1.34-9.65 µg mL-1).
- Seventeen isolates produced siderophores, and Pseudomonas aeruginosa SS183 showed ACC deaminase activity and 91% antifungal inhibition.
Conclusions:
- Pseudomonas azotoformans K22, E. hormaechei SS150, S. sciuri SS120, and B. cereus SS18/SS17 are identified as highly promising PGPB candidates.
- These selected isolates provide a strong foundation for developing microbial consortia for sustainable agriculture.
- Further validation is recommended for the development of effective bio-inoculants for low-fertility tropical soils.
