The Interaction And Effect Of Inoculation Of AM Fungi, Phosphate-Solubilizing Bacteria And Rhizobium On Growth Of Astragalus Sinicus L. At Different Phosphate Level

Phosphorus is one of the three major nutrient elements for the plants grown and only soluble-phosphorus can be absorbed by them. Phosphorus can easily be fixed under natural conditions, so it limited normal metabolism and growth of crops. Arbuscular mycorrhiza (AM) fungi are a kind of widespread microorganisms which contribute to soil systems, which form mutualistic symbiosis with more than 80% of land plants, not only facilitate plant mineral nutrient uptake, especialy phosphate, but also enhance tolerance to adverse environmental stress and plant diseases. Phosphate-solubilizing bacteria(PSB) in rhizosphere soil can be activated in the insoluble phosphate to improve the content of available phosphorus in soils. Rhizobium can be fixed atmospheric nitrogen. Root expansivly absorped various nutrients by the role of AM fungi. So mixed inoculation with plants can save phosphorus and improve yield.For the biodiversity and un-culturable separately nature of the AM fungi, it is unable for identification at the species level to discriminate the fungi based on morphology of spores. At the same time it was difficult to understand colonization of each AM fungi by the morphological characteristics when two or more species of AM fungi inoculated with plant. PCR based on discriminating primer opens the possibility of identifying distinct fungi in the roots and in soil. The aim of this study were:(Dstudy the capacity of several PSBs dissolved Ca3(PO4)2 (TCP) and rock phosphate(RP) in order to choose the hightest capacity of strain which used the grown-house experiment;â‘¡the interaction and effects of inoculation of AM fungi,PSB and Rhizobium on growth of Astragalus sinicus L. at different P level. The main results of this study were as follows:The pH of seven strains droped 3.88-5.18 in the TCP liquid medium. pH of B(Bacillus megatherium) strain was 3.88 while the amounts of soluble-P with E(Pseudomonas aeruginosa) strain was 288.30 mg/L. HPLC analysis detected six different kinds of organic acids. The results conferming their capacity to solubilize considerable amount of tricalcium phosphate in the medium by secreting organic acids. Furthermore, citric acid was only secreted by PA10 strain and PB5 strain. Maybe it was associated with the high amounts of solubilizing RP. In the RP liquid medium the amounts of soluble-P were decreased(PA10 strain 126.74 mg/L), comparatively higher amounts of soluble-P in the TCP liquid medium. A strong correlation between the cell densities,pH and soluble-P concentration of PA 10 was observed. In addition, statistically pH and the P solubilized were also strong negativly correlated. So it was a major method of phosphate solubilization that strains secreting organic acids droped pH of medium. Compared with all treatments, the inoculation of AM fungi,PA10 and 7653R significantly increased the plant growth at different P level and was the best combination in this experiment. There was a certain synergistic effect between them. Activity of Rhizobium is also closely related with wether or not the inoculation of AM fungi. The highest P concentration significantly decreased the colonization rate,the enzyme activity of SDH and ALP of AMF. Arbuscular abundance and enzyme activity of SDH and ALP were increased at the harvest of 4 weeks while arbuscular abundance began to disintegrat and collaps, enzyme activity of SDH and ALP were decreased at the harvest of 8 weeks. Nested-PCR was performed on the fresh roots with discriminating primers. The results indicated that the frenquencies of mix-inoculated AM fingus were significantly decreased by the highest P concentration. Furthermore, G. mosseae increased the colonization of G. intarardices and G. geosporum under the 10 mg/kg P-soil. With the increase of phosphorus concentration, the vitality and efficiency of G. mosseae and G. intraradices were more stable when G. geosporum was more sensitive to the phosphorus concentration,infection time and other microbial activity. The combination of nested PCR and freash roots, which was easily to extract DNA of AM fungi, successfully and accurately monitored the interaction between AM fungus.