MUTANT SCREENING AND MEDIUM OPTIMIZING OF A PHOSPHATE-DISSOLVING BACTERIA STRAIN Distribution of phosphobacteria in rhizosphere soils of four crops in Northeast China Analysis of the 16S rDNA PCR-RFLP and the Phosphate-Dissolving Capacity of Phosphate-Dissolving Bacteria Isolated from Rhizosphere of Mangrove in Southern China Phosphate dissolving capability and the affect of phosphate-dissolving bacteria in the rhizosphere on Sorghum bicolor