title: Contribution of arbuscular mycorrhizal fungi and/or bacteria to enhancing plant drought tolerance under natural soil conditions: effectiveness of autochthonous or allochthonous strains.
abstract: Autochthonous microorganisms [a consortium of arbuscular-mycorrhizal (AM) fungi and Bacillus thuringiensis (Bt)] were assayed and compared to Rhizophagus intraradices (Ri), Bacillus megaterium (Bm) or Pseudomonas putida (Psp) and non-inoculation on Trifolium repens in a natural arid soil under drought conditions. The autochthonous bacteria Bt and the allochthonous bacteria Psp increased nutrients and the relative water content and decreased stomatal conductance, electrolyte leakage, proline and APX activity, indicating their abilities to alleviate the drought stress. Mycorrhizal inoculation significantly enhanced plant growth, nutrient uptake and the relative water content, particularly when associated with specific bacteria minimizing drought stress-imposed effects. Specific combinations of autochthonous or allochthonous inoculants also contributed to plant drought tolerance by changing proline and antioxidative activities. However, non-inoculated plants had low relative water and nutrients contents, shoot proline accumulation and glutathione reductase activity, but the highest superoxide dismutase activity, stomatal conductance and electrolyte leakage. Microbial activities irrespective of the microbial origin seem to be coordinately functioning in the plant as an adaptive response to modulated water stress tolerance and minimizing the stress damage. The autochthonous AM fungi with Bt or Psp and those allochthonous Ri with Bm or Psp inoculants increased water stress alleviation. The autochthonous Bt showed the greatest ability to survive under high osmotic stress compared to the allochthonous strains, but when single inoculated or associated with Ri or AM fungi were similarly efficient in terms of physiological and nutritional status and in increasing plant drought tolerance, attenuating and compensating for the detrimental effect of water limitation.
authors.affiliation: Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Prof. Albareda 1, 18008 Granada, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Ortiz
authors.affiliation: Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Prof. Albareda 1, 18008 Granada, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Armada
authors.affiliation: Departamento de Proteccion Ambiental, Estación Experimental del Zaidín, CSIC, Prof. Albareda 1, 18008 Granada, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Duque
authors.affiliation: Department of Soil and Water Conservation, Centro de Edafología y Biología Aplicada del Segura, CSIC, P.O. Box 164, Campus de Espinardo, 30100 Murcia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Roldán
authors.affiliation: Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Prof. Albareda 1, 18008 Granada, Spain. Electronic address: rosario.azcon@eez.csic.es.
authors.forename: R
authors.initials: R
authors.lastname: Azcón
mesh_terms: D000222:Adaptation, Physiological; D001419:Bacteria / Q000378:metabolism*; D018533:Biomass; D055864:Droughts; D004602:Elements; D050296:Microbial Viability; D038821:Mycorrhizae / Q000502:physiology*; D018517:Plant Roots / Q000201:enzymology / Q000254:growth & development / Q000382:microbiology; D018520:Plant Shoots / Q000201:enzymology / Q000254:growth & development / Q000382:microbiology; D054046:Plant Stomata / Q000502:physiology; D011392:Proline / Q000378:metabolism; D012987:Soil; D029921:Trifolium / Q000382:microbiology* / Q000502:physiology*; D014867:Water / Q000737:chemistry
chemical_list: D004602:Elements; D012987:Soil; D014867:Water; D011392:Proline
keywords: Arbuscular mycorrhizal fungi and/or bacteria; Autochthonous and allochthonous microorganism; Drought; Oxidative stress; Physiological responses