| Solubilizing micro-organisms have the biological characteristics of dissolving insoluble phosphate in soil solution into available phosphorus for plant's absorption and utilization. It's not only can increase the available phosphorus content in soil, enhance plant's absorption and utilization of phosphorus, but also can promote plant's growth. So solubilizing micro-organisms has become the focus of the practice of agriculture and forestry research in current. However, most of the research were focused on crops, the research of Eucalyptus was still rarely reported. In this research, solubilizing bacteria which were in three different varieties of Eucalyptus forest soil will be isolated, then select solubilizing bacteria with strong solubilizing ability and discuss the quantitative content of available phosphorus, pH, total organic acids content and the correlation between them through quantitative test;The ability of dissolving insoluble phosphate for inorganic phosphorus micro-organisms under simulated drought conditions; On this basis, the determination of net photosynthetic rate of plant, biomass and P content in plants though field experiments, and study the affection of phosphate-solubilizing bacteria on plant growth. At the same time, inorganic phosphorus micro-organisms with strong ability were identified by their characteristics and sequence analysis of 16S r DNA, and their taxonomic status were preliminarily determined by 16S r DNA sequences which had been registered in the Gen bank.(1) The selection of solubilizing micro-organisms in different Eucalyptus speciesSolubilizing bacteria were selected from three different varieties of Eucalyptus plantations soil, the research show that the number of organic phosphorus and inorganic phosphorus in willow Eucalyptus forest soil were greater than in the other two strains of Eucalyptus soil. Preliminary determination of the fertility of Meranti forest soil was relatively better than others. Inorganic PSMs P6, P7, P8, P19, P25, P26 and P28 have strong solubilizing ability, and there was correlation between its culture medium pH and dissolved phosphorus content. Organic PSMs YP8, YP16, YP17, YP18, YP26, YP27, YP29, YP30 have strong solubilizing ability, and there was no significant correlation between medium pH and dissolved phosphorus content.(2) Activity of strainsThe dissolving ability of seven strains inorganic phosphorus of strong dissolving ability were different. Strain P6 has the strongest dissolving ability to aluminum phosphate, at 16.920μg/ml; Strain P8 followed, at 12.779μg/ml, and there were no correlation between aluminum phosphate content in culture medium and the pH value. The ability of seven strains dissolve iron phosphate was not very strong, only the activity of strain P6, P7, P19 was greater than the blank solution. There were correlation between medium iron phosphate content and pH. The activity of seven strains to calcium hydrogen phosphate was relatively strong, up to 138.120~410.550μg/ml, significantly greater than other substances in phosphorus solubilizing activity; and there were no correlation between dissolved calcium hydrogen phosphate content and pH.The solubilizing ability of seven inorganic phosphate bacteria occurs irregular changes under PEG simulated drought stress. Under 10% PEG treatment, the dissolved activity of strains was significantly different: P7>P8>P19>P26>P25>P28>P6; under 20% of the treatment, the dissolved activity was P7>P26>P19>P25>P8>P28>P6; under 30% of the treatment, the dissolved activity was P8>P19>P26>P25>P28>P6>P7. Overall, the dissolved activity of different strains was decreased with the stress intensity increases. The study reveals that strains P8 and P19 have strong resistance capability to dry.Five inorganic PSMs were cultured in inorganic phosphate liquid. There were more than one peak about the available phosphorus content of strains P6, P7, P8 and P25 in the liquid culture with the time go on. Generally in the d3 (d3 represent 3 days and so on) got to the first best value; however, the solubilizing capacity about strain P19 was declined during the culturing process.There was downward trend about the value of medium pH over the time, and the pH of P25, P7 were decreased during the d5 ~ d7. The content of total organic acids in medium was rise over the time in addition to P6.(3) The molecular classification and identification of the PSMsThe identification results of inorganic phosphate solubilizing bacteria on the filter out of the sequencing comparison showed that the dissolving phosphate bacteria in Eucalyptus forest soil mainly Bacillus sp., accounting for 69.23%. In addition, some dissolving phosphate bacteria were staphylococcus and Lysinibacillus. Their l6S r DNA sequences had been registered at Gen Bank. (4)The effect of PSMs on the growth of Eucalyptus seedlings Field experiments show that different treatments of PSMs promote the growth of Eucalyptus seedlings. The fresh weight and dry weight about treatment plants 2,20,21,22 were increase by 60% or more, and the tree height and diameter of treatment plants 20,21,22 increase more than 30% under single strain treatment; at the same the biomass of Eucalyptus were also increased under mixed bacteria treatment and organic fertilizer & strain treatment.The content of available phosphorus in plants has greatly improved over the blank. Under single strain treatment, the largest increase was treatment 2, followed by treatment 22; however, under mixed treatment, treatment 26&28 have better treatment effect than the single strain treatment in promoting the growth of Eucalyptus seedlings. Different treatment increased the net photosynthetic rate of Eucalyptus, especially single-strain treatment 2, 3, 20, 21, 22, 23; of which treatment 23 has largest increase, followed by treatment 2; the largest increase in mixed strain treatment was treatment 7, however treatment 17 has largest increase under organic fertilizer & strain treatment. There were widely different about the content of chlorophyll under different treatment, and the content of chlorophyll of treatment 2,3,5,12,14 was negative. Compwered with the blank, under single strain treatment, the largest increase was treatment 23, followed by treatment 21; under mix bacteria treatment, the largest increase was treatment 40; under organic fertilizer & strain treatment was treatment 38.Comprehensive consideration of various indicators above, the writer suggest that the strain P6, P7, P8, P19 have strongest effect on the growth of Eucalyptus, and have strong ability of dissolving phosphate.
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