The Improved P Uptake Of Maize Combinedly By Inoculation With Dark Septate Endophytes (DSE) And Phosphate Solubilizing Bacteria To Insoluble Phytin Under The Limited Available Phosphorus

Dark septate endophytes(DSE)are multifunctional root endophytic fungi that colonized in different plant roots,worldwide distribution,and play an important role in growth promotion and stress resistance to host.Our previous research revealed that DSE promotes the use of insoluble phosphorus in maito be documented.Phosphate-solubilizing bacteria can activate insoluble inorganic and ze,while its mechanism remains organic phosphorus(P)in soil.Interactions between microorganisms play an important role in the soil P mobilization and plant P nutrition in the soil with the co-exiting of plant-DSE-phosphate-solubilizing bacteria.In the present study,a high effective phosphate solubilizing bacterium(BP01)was isolated from the soil of maize field,and it was identified by morphological and molecular biology.The bacterial strain(BP01)and the high effective phosphate solubilizing DSE(Exophiala pisciphila,H93)were dually inoculated to maize roots in the pot cultures with limited available P but added enough insoluble P(phytin)in green house.The inoculation effects on the P absorption of maize were evaluated.The main results were followings:1.The phosphate-dissolving ability of a DSE stain(E.pisciphila,H93)for phytin was evaluated.A DSE strain(E.pisciphila,H93)was obtained with the phosphate-solubilizing capability of 414 μg L-1 in the shake-flask culture.It was found that H93 possess a strong ability on dissolving phytin by its secreting acid phosphatase.It exhibited a relative higher acid phosphatase activity than alkaline phosphatase activity in its fermentation broth.Beside,H93 also decreased the pH of the medium,which would further enhance the phosphate-solubilizing process.2.Phosphate-solubilizing bacteria were isolated and screened from the field soil of maize by the selective medium with phytin as the sole phosphorus source.A bacterial strain(BP01)was obtained with the phosphate-solubilizing capability of 629.67 μg L-1 in the shake-flask culture.The BP01 strain was identified as Pseudomonas sp.based on its morphology and 16S rDNA characters.The stain of BP01 exhibited a relative higher acid phosphatase activity,with 82.62 EU in its fermentation broth.3.The dual inoculation with BP01 and H93 to the pot cultured maize roots showed that the biomass,shoot high,stem diameter and phosphorus concentration of maize were significantly higher than those of the non-inoculation controls or single inoculation.Besides,the soluble phosphorus content,acid and alkaline phosphatase activities in the dual inoculation culture substrate were also significantly higher than the controls.Compared with the controls,available phosphorus content,acid phosphatase activity,alkaline phosphatase activity,phytase activity were increased 38.17%,39.38%,22.47%and 63.04%,respectively.However,the pH in the dual inoculation culture substrate decreased significantly compared to the controls.Based on these results,we suggested that BP01 and H93 activate insoluble phosphorus in soil combinedly by enzymes and decreased the culture substrate pH thus transforming insoluble phosphorus into plant available phosphorus,and further enhance the growth of maize.