Mechanism Of Inter-specific Interactions Among Arbuscular Mycorrhizal Fungi And Phosphate Solubilizing Bacteria To Improve P Uptake Of Maize

Interactions between microorganisms play a significant role in soil P mobilization and plant P improvement in ecological system with the trinity of plant-AM fungi-bacteria. However, the mechanisms and ecological function have been not well understood. In the present study, mechanisms of the interactions between different species of AM fungi, AM fungi and phosphate-solubilizing bacteria to accelerate organic P mineralization and improve plant P uptake were studied using a microcosm system and molecular microbial ecology techniques [Real time-qPCR, T-RFLP,13C-DNA-SIP and high-throughput sequencing (454 sequencing platform and Illumina MiSeq sequencing platform)] at both physiological and molecular levels under the conditions of pot and field experiment. The main results are listed below:1. When the same root was simultaneously colonized by different species of AM fungi-Rhizophagus intraradices、Funneliformis mosseae and Gigaspora margarita, Rhizophagus intraradices played a major role in the growth and p uptake of maize and was considered as a dominant species in the community. However, F. mosseae were regarded as a non-dominant species based on its contribution to maize in growth and P uptake. The dominance of Gig. margarita was somewhere between other two AM fungi in the community. The competition of R. intraradices was more intense than F. mosseae for resources in limited space, while competition of Gig. margarita was weaker than F. mosseae. However, intensity of competition in Gig. margarita was gradually enhanced with the stage of growth and development for maize.2. Water stress affected the interactions between different species of AM fungi. The contribution of R. intraradices to growth and P uptake of maize was not influenced by drought. However, drought led to more intense competition between R. intraradices and F. mosseae, while the relationship between F. mosseae and Gig. margarita was gradually transformed from competition to cooperation.3. Host plant species significantly changed the bacteria and alkaline phosphatase (ALP)-harboring bacterial community structure, interactions between AM fungi and these bacteria accelerated the mineralization of soil organic phosphorus, and the effects of their interactions in maize was stronger than those in soybean. Analysis of AM fungal diversity in the maize-soy bean intercropping system showed that AM fungi in soil were mainly affiliated to genera of Funneliformis and Rhizophagus. Host species but not organic P level significantly influenced community structure of bacteria and ALP-harboring bacteria attached on hyphae of AM fungi. ALP-harboring bacterial groups mainly included Xanthomonas and Delftia for maize, while these groups belonged to Xanthomonas and Sinorhizobium for soybean.4. The phosphate-solubilizing bacterias (PSB) screened from the hyphae of AM fungi in hyphosphere soil under field crop conditions were detected that they could colonize on the surface of the R. intraradices hyphae and the community of PSB attached on hyphae differed from those in hyphosphere soil using artificial inoculation experiment and C-DNA-SIP technique.