ABSTRACT
OBJECTIVE: To improve use efficiency of phosphorus in latosolic red soil and to explore mechanism of phosphate solubilization. METHODS: Pikovskaya and National Botanical Research Institute' s Phosphate broth were used to isolate a phosphate-solubilizing bacterium coded as C5-A from the rhizosphere soil of peanut. According to its morphological, physiological, biochemical properties and its 16S rRNA sequence, its position in phylogenetic development tree was defined. By measuring changes in pH of the National Botanical Research Institute's Phosphate solution in which C5-A was incubated, phosphate solubilizing capacity was determined. Through fermentation, effects of carbon and nitrogen sources on the capacity of strain C5-A were investigated. Kinds and concentrations of organic acids in the cultures different in N sources were also determined by HPLC. RESULTS: The strain was identified as Burkholderia cepacia, which is stable in hereditary. In aluminum phosphate and ferric phosphate solutions, its P solubilizing capacity was negatively related to pH. It solubilized tricalium phosphate, aluminum phosphate, ferric phosphate and rock phosphates powder, and could dissolve as much as 125.79 mg/L, 227.34 mg/L, 60.02 mg/L and 321.15 mg/L P, respectively. For RPP, P solubilizing capacity of the strain was related to type and concentration of the powder. When using maltose and ammonium oxalate as C and N sources, the strain displayed its highest P solubilizing capacity. HPLC analysis detected 10 organic acids in the culture, namely: oxalic acid, acetic acid, malic acid, lactic acid, citric acid, cuccinc acid and 5 unknown organic acids. Interestingly, it is acetic acid rather than gluconic acid being the most important organic acid affecting P solubilization. CONCLUSION: The strain isolated from the rhizosphere soil of peanut plants growing in a red soil field can dissolve hard-to-solve inorganic salts, and is a promising microbial resource for development of high efficiency biological phosphorus fertilizer for latosolic red soil.
