Isolation and identification of phosphate solubilizing bacteria from rice rhizosphere soil, and promoting effect on rice plant growth

Objective To determine the ability of phosphate dissolving of phosphate solubilizing bacteria(PSB)in rice rhizosphere, and study the effect of PSB on soluble phosphorus contents in rice plants and rhizosphere soil.

Method Two bacteria strains NDW1 and NDW3 with strong ability of dissolving Ca₃(PO₄)₂ were isolated from rice rhizosphere soil based on the halo zone formation on media due to phosphate solubilization, and identified by 16S rDNA method. Phosphorus dissolving conditions of two strains were optimized by orthogonal test with NBRIP as the basic medium. The production of indole-3-acetic acid(IAA) were determined. The effects of NDW1 and NDW3 on promotion of rice growth, the soil available phosphorus contents and plant total phosphorus contents were studied.

Result NDW1 and NDW3 were identified as Enterobacter sp. and Serratia sp.. The best combination of carbon, nitrogen source and pH for phosphate solubilition by NDW1 and NDW3 were both the combination of glucose, peptone and pH 6. The highest phosphorus contents dissolved by NDW1 and NDW3 were 294.95 and 312.93 μg·mL^-1 after 24 h incubation, respectively. Both PSB could produce IAA. NDW3 significantly increased the shoot height, root length, maximum leaf length and above-ground dry mass of rice plant in both soil culture and sand culture. NDW3 also significantly increased the contents of soil available phosphorus and rice total phosphorus under both culture conditions.

Conclusion Enterobacter sp. NDW1 and Serratia sp. NDW3 isolated from rice rhizosphere soil have strong ability of phosphate dissolving. The growth promoting effect of NDW3 for rice plant is better than that of NDW1.