Plant and Soil

, 287:35 | Cite as

Phosphate solubilization activity of rhizobia native to Iranian soils

  • H.A. Alikhani
  • N. Saleh-Rastin
  • H. AntounEmail author
Original Paper


Agricultural soils in Iran are predominantly calcareous with very low plant available phosphorus (P) content. In addition to their beneficial N2-fixing activity with legumes, rhizobia can improve plant P nutrition by mobilizing inorganic and organic P. Isolates from different cross-inoculation groups of rhizobia, obtained from Iranian soils were tested for their ability to dissolve inorganic and organic phosphate. From a total of 446 rhizobial isolates tested for P solubilization by the formation of visible dissolution halos on agar plates, 198 (44%) and 341(76%) of the isolates, solubilized Ca3(PO4)2 (TCP) and inositol hexaphosphate (IHP), respectively. In the liquid Sperber TCP medium, phosphate-solubilizing bacteria (Bacillus sp. and Pseudomonas fluorescens) used as positive controls released an average of 268.6 mg L−1 of P after 360 h incubation. This amount was significantly (P < 0.05) higher than those observed with all rhizobia tested. The group of Rhizobium leguminosarum bv. viciae mobilized in liquid TCP Sperber medium significantly (P < 0.05) more P (197.1 mg L−1 in 360 h) than other rhizobia tested,. This group also showed the highest dissolution halo on the TCP solid Sperber medium. The release of soluble P was significantly correlated with a drop in the pH of the culture filtrates indicating the importance of acid production in the mobilization process. None of the 70 bradyrhizobial isolates tested was able to solubilize TCP. These results indicate that many rhizobia isolated from soils in Iran are able to mobilize P from organic and inorganic sources and this beneficial effect should be tested with crops grown in Iran.


calcium phosphate legumes inositol hexaphosphate PGPR pH Rhizobium 



The authors are grateful to professor Malakouti head of the Soil and Water Research Institute in Tehran and to the staff of the Department of Soil Biology of the same Institute for their help with the rhizobial collection and for their constructive discussions. Many thanks to professor Ghannadha for his help in the statistical analyses and the interpretation of the results, and to Miss Pashaky for her excellent technical assistance. Financial support for this investigation was provided by grants from the Iranian Government “Studies and Researches Between Universities” program for collaboration between the Universities of Tehran and Rafsanjan.


  1. Abd-Alla M H (1994) Use of organic phosphorus by Rhizobium leguminosarum bv. viciae phosphatases. Biol. Fertil. Soils 8:216–218CrossRefGoogle Scholar
  2. Antoun H A, Beauchamp C J, Goussard N, Chabot R, Lalande R (1998) Potential of Rhizobium and Bradyrhizobium species as plant growth promoting rhizobacteria on non-legumes: effect on radishes (Raphanus sativus L.). Plant Soil 204:57–67CrossRefGoogle Scholar
  3. Barea J M, Azcón R, Azcón-Aguilar C (2002) Mycorhizosphere interactions to improve plant fitness and soil quality. Antonie van Leeuwenhoek 81:343–351PubMedCrossRefGoogle Scholar
  4. Chabot R, Antoun H, Kloepper J W, Beauchamp C J (1996) Root colonization of maize and lettuce by bioluminescent Rhizobium leguminosarum biovar phaseoli. Appl. Environ. Microbiol. 62:2767–2772PubMedGoogle Scholar
  5. Goldstein A H (1986) Bacterial solubilization of mineral phosphates: historical perspectives and future prospects. Am. J. Altern. Agric. 1:51–57Google Scholar
  6. Gupta R, Singal R, Shankar A, Kuhad R C, Saxena R K (1994) A modified plate assay for screening phosphate solubilizing microorganisms. J. Gen. Appl. Microbiol. 40:255–260Google Scholar
  7. Halder A K, Chakrabartty P K (1993) Solubilization of inorganic phosphate by Rhizobium. Folia Microbiol. 38:325–330Google Scholar
  8. Mehata S, Nautiyal C S (2001) An efficient method for qualitative screening of phosphate-solubilizing bacteria. Curr. Microbiol. 43:51–56CrossRefGoogle Scholar
  9. Nahas E (1996) Factors determining rock phosphate solubilization by microorganisms isolated from soil. World J. Microbiol. Biotechnol. 12:567–572CrossRefGoogle Scholar
  10. Nautiyal C S (1999) An efficient microbiological growth medium for screening phosphate solubilizing microorganisms. FEMS Microbiol. Lett. 170:265–270PubMedCrossRefGoogle Scholar
  11. Olsen S R and Sommers L E 1982 Phosphorus. In Methods of Soil Analysis, Part 2-chemical and Microbiological Properties, 2nd edn., Ed. Page AL. Am Soc. Agron. and Soil Sci. Soc. A. Madison, Wisconsin, USAGoogle Scholar
  12. Peix A, Rivas-Boyero A A, Mateos P F, Rodriguez-Barrueco C, Martinez-Molina E, Velazquez E (2001) Growth promotion of chickpea and barley by a phosphate solubilizing strain of Mesorhizobium mediterraneum under growth chamber conditions. Soil Biol. Biochem. 33:103–110CrossRefGoogle Scholar
  13. Richardson A E (2001) Prospects for using soil microorganisms to improve the acquisition of phosphorus by plants. Aust. J. Plant Physiol. 28:897–906Google Scholar
  14. Robson A D, O’Hara G W, Abbott L K (1981) Involvement of phosphorus in nitrogen fixation by subterranean clover (Trifolium subterraneum L.). Aust. J. Plant Physiol. 8:427–436CrossRefGoogle Scholar
  15. Rodriguez H, Fraga R (1999) Phosphate solubilizing bacteria and their role in plant growth promotion. Biotech. Adv. 17:319–339CrossRefGoogle Scholar
  16. SAS, Institute Inc 1990 SAS procedure guide version 6 edn. SAS Institute Inc Cary, NC, 705 pGoogle Scholar
  17. Schloter M, Wiehe W, Assmus B, Steindl H, Beke H, Höflich G, Hartmann A (1997) Root colonization of different plants by plant-growth-promoting Rhizobium leguminosarum bv. trifolii R39 studied with monosporic polyclonal antisera. Appl. Environ. Microbiol. 63:2038–2046PubMedGoogle Scholar
  18. Silva Filho G N, Vidor C (2000) Phosphate solubilization by microorganisms in the presence of different carbon sources. R. Bras. Ci. Solo. 24:311–319Google Scholar
  19. Sperber J I (1958) The incidence of apatite solubilizing organisms in the rhizosphere and soil. Aust. J. Agric. Res. 9:778–781CrossRefGoogle Scholar
  20. Somasegaran P and Hoben H J 1994 Handbook for Rhizobia – Methods in Legume–Rhizobium Technology. Springer-Verlag, New YorkGoogle Scholar
  21. Vincent J M 1970 A Manual for the Practical Study of Root Nodule Bacteria. IBP handbook 15 Blackwell Scientific Publications, OxfordGoogle Scholar
  22. Whitelaw M A (2000) Growth promotion of plants inoculated with phosphate-solubilizing fungi. Adv. Agron. 69:99–151CrossRefGoogle Scholar
  23. Yanni Y G, Rizk R Y, Abd El-Fattah F K, Squartini A, Corich V, Giacomini A, de Bruin F, Rademaker J, Mayra-Flores J, Ostrom P, Vega-Hernandez M, Hollingsworth R I, Martinez-Molina E, Mateos P, Velazquez E, Wopereis J, Triplett E, Umali-Garcia M, Anarna J A, Rolfe B G, Ladha J K, Hill J, Mujoo R, Ng P K, Dazzo F B (2001) The beneficial plant growth-promoting association of Rhizobium leguminosarum bv. trifolii with rice roots. Aust. J. Plant Physiol. 28:845–870Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  1. 1.Department of Soil Science, College of AgricultureTehran UniversityTehranIran
  2. 2.Département des Sols et de Génie AgroalimentaireUniversité Laval QuébecCanada

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