Abstract:

In this experiment, solubilization of inorganic phosphorus and organic phosphorus by standard strain CGMCC 1.2540T of Rhizobium tropici Martinez-Romero et al. and 23 rhizobia strains, which were isolated from woody legume plants in the Jianfengling Nature Reserve, Hainan Province, was investigated. By a qualitative test of phosphorus-solubilized halo, and quantitative test of content of available P in the medium with inorganic phosphorus of Ca₃(PO₄)₂ as the sole source of phosphorus, twenty-two strains were demonstrated to produce the phosphorus-solubilized halo, and there were significant differences in the diameter ratio between the halo and colony. The strains that produced the available phosphorus in the medium to be more than 219.13 mg·L^-1 included 9 strains of caf 333, caf 443, caf 336, caf 278, caf 344, caf 444, caf 276, caf 436 and caf 341. The strain of caf 438 had the weakest capacity of phosphorus-solubilized while caf 341 had the strongest capacity to increase the available phosphorus in the medium, respectively by 0.80 mg·L^-1 and 628.57 mg·L^-1. Different strains of same species which were isolated from the same host showed significantly different capacity of phosphorus-solubilized. In the medium which lecithin was used as the sole source of phosphorus, all 24 strains tested did not displayed any phosphorus-solubilized halo.

Key words: tree legume, rhizobia, phosphorus-solubilized halo, phosphate solubilization, content of available P