Study On Effects And Mechanisms Of Penicillium Oxalicum On Solubilization Of Insoluble Phosphate From Calcareous Soils In North China

Phosphate-dissolving microorganisms in soils play an important role in phosphorous cycling, converting insoluble phosphate into soluble forms. Isolation and selection of P-dissolving microorganisms were carried out with selected calcareous soils from North China. Three strains of P-dissolving fungi were obtained. Two of them, PS and Pnl were identified as Penicillium oxalicum, and the other one Aspergillus sp. Solubilization of mineral and soil phosphates by the P-dissolving fungi and it effect on plant growth were studied. The results are as following:1.In plate assay, the strain of PS showed higher capability to dissolve Ca3(P04)1 Ca~H2(PO4)6 5H2O~ CaHPO4~ FePO4 and bone meal than A1CC2085 I and ATCC 14581. However, in broth assay, P8 consistently demonstrated higher efficiency to dissolve Morocco rock phosphate (MR.P) than ATCC2O58 1. Results of incubation of MIRP with PS and Pnl, using N03-N and N7H4-N as N sources, indicated that both N03-N and NH4-N in broth enhanced the release of P in MRP, and that N03-N form was more efficient than NH4-N.2.Application of Penicillium P8 improved crop growth and plant uptake of N, P, K from soils. The effect of P8 with peanut was more significant than that with corn and canola. Application of phosphate fertilizer reduced the effectiveness of Penicillium P8 in increasing biomass at the first crop. But in the second crop, P8 showed a significant influence on biomass of plants. With P fertilizer application, P8 showed capability to increase plant uptake of P.3.Application of Penicillium PS to soils increased the availability of insoluble P component of the soil, especially P in the form of Ca10-P. Peniciiium126P8 could also increase the solubility of insoluble mineral phosphates applied to the soil, such as Ca3(P04),, Ca~H2(PO4)6 and MRP.4.GFP and GUS genes were transformed into Peniillium P8 and expressed excessively. Environment conditions influenced the survival of Penicillium P8 in soils. A higher survival rate was found with low temperature and low moisture of soils. Type of carriers and application methods affected the survival rate of Penicillium P8 in soils, with the selected soil as the best carrier and base application superior to seed inoculation.5.Penicillium P8 could use urea, NOR-N and NH4-N as N source during incubation with MIRP and Ca3(P04)2. Increase of soluble P level in the broth significantly decreased activity of acid-phosphatase, reduced the concentration of organic acids, protein and polysaccharide exuded by strain P8. Adding insoluble phosphate to the broth resulted in the excessive exudation of acid-phosphatase, organic acids, protein and polysaccharide. It is proposed that the exudes derived from Penicillium P8 play an important role in dissolving the insoluble P in the system, and that the process can be induced by P stress.