Relationship between in vitro characterization and comparative efficacy of plant growth-promoting rhizobacteria for improving cucumber salt tolerance

• Published in: Archives of microbiology Vol. 198; no. 4; pp. 379 - 387
• Main Authors: Nadeem, Sajid Mahmood, Ahmad, Maqshoof, Naveed, Muhammad, Imran, Muhammad, Zahir, Zahir Ahmad, Crowley, David E.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2016; Springer Nature B.V
• Subjects: Acetic acid; Bacillus megaterium - physiology; Bacteria; Bacterial Physiological Phenomena; Biochemistry; Biomedical and Life Sciences; Biotechnology; Carbon-Carbon Lyases; Carboxylic acids; Cell Biology; Cucumis sativus - drug effects; Cucumis sativus - growth & development; Cucumis sativus - microbiology; Cucumis sativus - physiology; Ecology; Environmental science; Gene Expression Regulation, Bacterial; Genes, Bacterial - genetics; Indoleacetic Acids - metabolism; Life Sciences; Microbial Ecology; Microbiology; Original Paper; Plant growth; Pseudomonas fluorescens - physiology; Rhizosphere; Salinity; Salt tolerance; Salt-Tolerance - physiology; Siderophores - genetics; Sodium chloride; Sodium Chloride - pharmacology; Soil Microbiology; Soil sciences; Pakistan; Characterization; PGPR; Growth; Cucumber; Stress; Salinity
• ISSN: 0302-8933; 1432-072X
• DOI: 10.1007/s00203-016-1197-5

Phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid (ACC)-deaminase activity and production of siderophores and indole acetic acid (IAA) are well-known traits of plant growth-promoting rhizobacteria (PGPR). Here we investigated the expression of these traits as affected by salinity for three PGPR strains ( Pseudomonas fluorescens , Bacillus megaterium and Variovorax paradoxus ) at two salinity levels [2 and 5 % NaCl (w/v)]. Among the three strains, growth of B. megaterium was the least affected by high salinity. However, P. fluorescens was the best strain for maintaining ACC-deaminase activity, siderophore and IAA production under stressed conditions. V. paradoxus was the least tolerant to salts and had minimal growth and low PGPR trait expression under salt stress. Results of experiment examining the impact of bacterial inoculation on cucumber growth at three salinity levels [1 (normal), 7 and 10 dS m −1 ] revealed that P. fluorescens also had good rhizosphere competence and was the most effective for alleviating the negative impacts of salinity on cucumber growth. The results suggest that in addition to screening the PGPR regarding their effect on growth under salinity, PGPR trait expression is also an important aspect that may be useful for selecting the most promising PGPR bacterial strains for improving plant tolerance to salinity stress.