Study On Phosphate-solubilizing Characteristic And Promoting Effect Of Phosphobacteria Isolated From Rhizosphere Of Medicago Sativa And Triticum Aestivum

Phosphate-dissolving microorganisms in soil play an important role in phosphrous cycling and converting insoluble phosphate into its soluble forms. Isolation and selection of P-dissolving microorganisms were carried out from Rhizosphere of wheat(Triticum　aestivum) and alfalfa(Medicago sativa). The 12 strains of high performance P-dissolving bacteria were obtained. Capability of P-solublizing, dynamic of P-solublizing and characteristic of P-solublizing of 4 strains was studied. The effects of 10 strains on Oat (Avena sativa) growth were also investigated through a series of pots and field plots experiments. The results are as follows: 1. The total of 368 Phosphobacteria strains were isolated from Rhizosphere of wheat and alfalfa, but the numbers of the strains found in different Rhizosphere sections were various, they were: Soil adhering to roots (RS)> Soil away from roots (NRS)> Rhizoplan of roots( RP)> Histoplan (HP). Among them, there were 66 strains which showed obvious Phosphorus hole around strains. Moreover, 12 strains were screened by measured the capacity of dissolving Phosphorus which more than 100mg/l in broth assay. 2. As far as different strains, effect of culture time on P-solublizing, pH, and total organic acids were difference, but relationship between changes of organic acids, pH and P-solubilizing were significance. 3. In broth assay, 4 strains showed high capability to dissolve Ca3-P and Ca8-P, but Ca10-P-dissolving abilities of them were low; pH were decreased in all treatments and the organic acids content were lowest in medium of Ca10-P sources. 4. Salt tolerance of 4 strains was high. Lower or higher NaCl concentrations was not benefit for strains to act there abilities of P-solubilizing, different strains have different NaCl concentrations for maximum P-solubilizing, pH was not sensitive to NaCl concentrations, however, changes of organic acids with NaCl concentrations were resemble to P-solubilizing except Lx191. 5. In orthogonal experiment(L934), We discovered that every combination included varies sources of carbon, sources of nitrogen, pH and salt concentration had great influence on P-solubilizing abilities of 4 PSB strains. Glucose was best source of carbon; all of them could use saccharose and Lx191 could use amylum. Effect of nitrogen sources, pH and salt concentration on P-solubilizing abilities, decrease of pH and organic acids excreted by 4 PSB strains existed great differences between various combination. 6. All of 4 PSB strains were oxygen moderate microorganism, but oxygen requirement of them were varies. 7. P-solubilizing abilities were highest when 4 strains inoculated in NBRIP broth assay, Perhaps the nutrition and condition offered by it were most profit for P-bacteria played there action of P-solubilizing, reduced pH of medium, excreted organic acids. The reliability of hole-based technique routinely screened P-solubilizing by plate assay method using PKO agar is questioned as many isolates, which did not produce any visible halo/zone on agar plates could solubilize insoluble inorganic phosphates in liquid medium. Yeast extract was non-essential ingredients in medium and 3 strains, P-solubilizing were limited by it. So we'd better use NBRIP broth assay when isolate phosphobacteria from soil in order to receive more high performance P-solubilizing microorganisms. 8. The results of interaction between 3 strains of NFB and 4 PSB were showed that: compared with inoculated PSB separately, abilities of P-solubilizing of some combinations were increased significance, appeared 1+1>2; some were decreased and appeared 1+1<2. Cultivated together made pH of medium ascend; Some combination's total organic acids were added, some were lessened. Compared with inoculated NFB separately, there results were difference when NFB inoculated with PSB together each other. 9. In pot experiments, under condition of NPF, application of 10 P-solubilizing strains improved Oat growth, above and under biomass, and Oat uptake of N, P from soil. Under condition of WHPF, 10 P-solubilizing bacteria increased above biomass of Oat, Lx174, Jx59, Lx22, Dm84 were benefit for under biomass; 6 strains, Lx81, Lx22, Jx59, Dx84, Lm126, Jm92 improved Oat uptake of N from soil. The effects of 10 strains on R/T had large dissimilarities between WHPF and NPF. 10. In field plot experiments, under the treatment of NPF, Jm170, Lm126, Dm84, Jm92, Lx174, Lx22, Lx191 improved above biomass of Oat; Lm126, Lx174, Dm84, Lx22, Lx191, Jm170 improved biomass of Oat under earth; After inoculated with Lx174, Lm126, Lx22, Dx68, Lx81, R/T was larger than control; All of 10 strains increasedcontent P of Oat stalk and root, N of Oat root; Lx22, Dm84, Lx191, Lx81, Lm126, Jx59, Dx68 were also profited for Oat stalk uptake of N. In the treatment of application half P-fertilizer to soils, Jm170,Jx59,Lx191,Jm92,Lm126 promoted above and under growth of Oat at same time, Lx22,Lx174 improved under growth of Oat also. R/T were increased when Oat inoculated with Lx22, Jx59, Lx174, Dx68, Lm126, Dm84, Lx191; all of 10 strains enhanced uptake P and N of Oat root. Lx22,Dm84,Lx191 ,Lx81,Lm126,Jx59,Dx68 promoted the content of P and Lx22, Dm84, Dx68 promoted the content of N of Oat stalk.