Solubilization of inorganic phosphates and growth emergence of wheat as affected by Azotobacter chroococcum mutants

Phosphate-solubilizing strains of A. chroococcum isolated from the wheat rh izosphere were evaluated for their ability to solubilize tricalcium phospha te (TCP), Mussoorie rock phosphate (MRP) and also for indole-acetic-acid (I AA) production. Strains were selected on the basis of the clearance zone on solid agar media of Pikovskaya and Jensen's media containing TCP, and phos phate solubilization in Jensen's liquid culture medium containing both TCP and MRP. Mutants of the best phosphate-solubilizing (TCP 1.52 mu g ml(-1) M RP 0.19 mu g ml(-1)), IAA-producing A. chroococum strain P-4, were develope d and screened for P solubilization and phytohormone production. Five mutan ts solubilized more P (in the range of 1.5-1.7 mu g/ml(-1) of TCP and 0.19- 0.22 mu g ml(-1) of MRP) than the parent strains. In vitro growth emergence studies of three wheat varieties, viz. C-306, WH-542 and HD-2009, showed b etter performance with phosphate-solubilizing mutants than with the parent strain.