Phosphate solubilizing bacteria and their role in plant growth promotion

The use of phosphate solubilizing bacteria as inoculants simultaneously inc reases P uptake by the plant and crop yield. Strains from the genera Pseudo monas, Bacillus and Rhizobium are among the most powerful phosphate solubil izers. The principal mechanism for mineral phosphate solubilization is the production of organic acids, and acid phosphatases play a major role in the mineralization of organic phosphorous in soil. Several phosphatase-encodin g genes have been cloned and characterized and a few genes involved in mine ral phosphate solubilization have been isolated. Therefore, genetic manipul ation of phosphate-solubilizing bacteria to improve their ability to improv e plant growth may include cloning genes involved in both mineral and organ ic phosphate solubilization, followed by their expression in selected rhizo bacterial strains. Chromosomal insertion of these genes under appropriate p romoters is an interesting approach. (C) 1999 Elsevier Science Inc. All rig hts reserved.