Screening of phosphate-solubilizing bacteria and their acting mechanisms in the rhizosphere of red clover.

Phosphate-solubilizing bacteria are important for agriculture,especially for legume plants,because they increase the available phosphorus in soils and improve the nodulation and nitrogen fixation of rhizobia.In the present paper,phosphate-solubilizing bacteria in the rhizosphere of red clover(Trifolium pratense L.) were screened based on PKO culture medium and molybdenum blue method.Total 21 strains were obtained,among which,10 strains had the ability to solubilize inorganic phosphate,the ratio of D/d(diameter of phosphate-dissolving zone / diameter of bacterial clone) varied from 1.13 to 1.62.And there were 5 strains had the ability to solubilize organic phosphate on Mengjinna organic culture medium,the ratio of D/d changed from 1.07 to 1.83.Strains lhs3,lhs11,and lhs15 could solubilize both inorganic phosphate and organic phosphate.In liquid culture,the available phosphate increment by inorganic phosphate-solubilizing bacteria changed from 5.0 mg/L to 596.3 mg/L and organic phosphate-solubilizing bacteria-0.03 mg/L to 58.34 mg/L using molybdenum blue method.Strains lhs6 and lhs8 had significantly higher ability in inorganic phosphate-solubilizing than other strains and strain lhs11 had the highest ability in organic phosphate dissolving.The ability of phosphate dissolving by bacteria was correlated to pH and organic acid,but not significantly.Strains lhs6,lhs8,and lhs11 showed great potential for agricultural use in microbiological fertilizer and deserved further study.