Isolation and the Phosphate Solubilizing Capacity of Italian Ryegrass Rhizosphere Phosphate-Solubilizing Microorganism

Phosphate-solubilizing microorganisms were isolated from Italian ryegrass rhizospheres using PKO inorganic and Mengjinna organic culture media.The phosphate solubilizing capacities were investigated from 41 strains based on phosphate-solubilizing circle and the molybdenum blue method.Among them,13 strains had an ability to solubilize inorganic phosphate and D/d(diameter of phosphate-dissolving zone/diameter of bacterial clone) value was from 1.13 to 4;and 28 strains had an ability to solubilize organic phosphate on Mengjinna organic culture medium and D/d value was from 1.13 to 16.4.In liquid culture,the available phosphate increment was detected using molybdenum blue method from 15.6 mg·L-1 to 557.2 mg·L-1 by inorganic phosphate-solubilizing microorganism and from 52 mg·L-1 to 341.6 mg·L-1 by organic phosphate-solubilizing bacteria.Strains b9,b13 and f5 had a significantly higher ability of inorganic phosphate-solubilizing than others did.Strains B1 and B3 had a higher ability of organic phosphate-dissolving showing great potential for agricultural use in microbiological fertilizer and deserve further study.There was a significant correlation between the phosphate solubilizing capacity of inorganic phosphate dissolving microorganism and the pH of medium,whereas there was no such correlation for organic phosphate dissolving bacteria.