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- Title
Rhizosphere bacteria of Costularia spp. from ultramafic soils in New Caledonia: diversity, tolerance to extreme edaphic conditions, and role in plant growth and mineral nutrition.
- Authors
Gonin, Mathieu; Gensous, Simon; Lagrange, Alexandre; Ducousso, Marc; Amir, Hamid; Jourand, Philippe
- Abstract
Rhizosphere bacteria were isolated from Costularia spp., pioneer sedges from ultramafic soils in New Caledonia, which is a hotspot of biodiversity in the South Pacific. Genus identification, ability to tolerate edaphic constraints, and plant-growth-promoting (PGP) properties were analysed. We found that 105 colony-forming units per gram of root were dominated by Proteobacteria (69%) and comprised 21 genera, including Burkholderia (28%), Curtobacterium (15%), Bradyrhizobium (9%), Sphingomonas (8%), Rhizobium (7%), and Bacillus (5%). High proportions of bacteria tolerated many elements of the extreme edaphic conditions: 82% tolerated 100 μmol·L-1 chromium, 70% 1 mmol·L-1 nickel, 63% 10 mmol·L-1 manganese, 24% 1 mmol·L-1 cobalt, and 42% an unbalanced calcium/magnesium ratio (1/16). These strains also exhibited multiple PGP properties, including the ability to produce ammonia (65%), indole-3-acetic acid (60%), siderophores (52%), and 1-aminocyclopropane-1-carboxylate (ACC) deaminase (39%); as well as the capacity to solubilize phosphates (19%). The best-performing strains were inoculated with Sorghum sp. grown on ultramafic substrate. Three strains significantly enhanced the shoot biomass by up to 33%. The most successful strains influenced plant nutrition through the mobilization of metals in roots and a reduction of metal transfer to shoots. These results suggest a key role of these bacteria in plant growth, nutrition, and adaptation to the ultramafic constraints.
- Subjects
NEW Caledonia; RHIZOBACTERIA; PLANT growth; PLANT nutrition; SOIL microbiology
- Publication
Canadian Journal of Microbiology, 2013, Vol 59, Issue 3, p164
- ISSN
0008-4166
- Publication type
Article
- DOI
10.1139/cjm-2012-0570