AM真菌与菌丝际解磷细菌互作增强土壤磷活化利用的机制

P mines are being exhausted in China at a accelerating rate,while lagre amount of P resource is being accumulated in soil via fertilizer supply. How to enhance the utilization of soil P has been concerned as an important issue for sustainable food production. One of the key approaches to enhance soil P utilization is to strengthen the positive interactions between AM fungi and the phosphate-solublizing-bacteria that colonizes on the fungal hyphae. In this project, the compartmented rhizobox, plant-AM fungi axenic-culturing method and 13C-Nano-SIMS methods will be used to trace the flow of isotopic lablled photosynthetic products through plant root-AM fungal mycelium-hyphal associated bacteria; molecular approached, e.g. 13C-DNA-SIP、qRT-PCR、T-RFLP, will be employed to investigate the response of metabolic activity and function of phosphate-solublizing-bacteria to the species of plant-hosts, AM fungal partiners and soil available P contents; to test the effects of AM fungal hyphae exudates on phosphate-solublizing-bacteria metabolic activity and function, or of the bacteria exudates on AM fungal activity and function. Our study will supply direct evidences to uncover the mechanisms of the synergistic interactions by which AM fungi and phosphate-solublizing-bacteria associates strengthen the mobilization of soil P.

我国的磷矿资源正被加速耗竭，这些磷大部分以肥料方式进入农田并被土壤固持，如何提高土壤磷的利用是关乎粮食生产可持续性的重大问题；利用作物与AM真菌共生关系强化土壤磷的活化利用是提高磷资源利用的关键途径之一，揭示AM真菌与定殖于菌丝上的细菌相互作用的效应及机制是国际前沿课题。本项目拟以三室隔网根箱法、AM真菌与植株双重纯培养法、13C-Nano-SIMS方法跟踪植物光合产物在根系-AM真菌-菌丝际细菌连续体系中迁移转化过程，以13C-DNA-SIP、qRT-PCR、T-RFLP技术研究菌丝际解磷细菌的代谢活性和功能随宿主植物种类、AM真菌种类和土壤有效磷含量变化的响应机制，揭示菌丝分泌物对解磷细菌、解磷细菌代谢产物对AM真菌的生长和活化利用土壤磷的功能的影响，从而阐明AM真菌与菌丝际解磷细菌协同强化作物利用土壤磷的机理，为充分挖掘作物高效利用土壤磷养分资源的潜力提供理论依据。

为了揭示AM真菌和菌丝际解磷细菌相互作用增强土壤累积态磷活化利用、改善植物磷效率的机制，本项目结合室内模拟和田间原位的方法研究了AM真菌和解磷细菌协同互作促进土壤磷活化的机制，为作物高效利用土壤磷资源提供理论依据和技术支撑。通过根箱法和田间原位埋盒法阐明了AM真菌与解磷细菌互作增强土壤有机磷活化的机理，以及菌丝际解磷细菌的活性和功能随宿主植物种类、AM真菌种类和土壤有效磷水平变化的响应机制；利用隔网根箱培养系统和13C同位素示踪技术跟踪植物光合产物在植物-AM真菌-解磷细菌连续体中的流动和分配；获得了以下主要结果：（1）证明氮形态能够强化AM真菌与解磷细菌互作对土壤有机磷的矿化；（2）证明菌丝际土壤有机磷的周转受到C:P比的调控；（3）证明土著AM真菌对玉米磷营养的贡献；（4）证明植物的光合产物能够通过菌丝传递到菌丝际土壤中并被解磷细菌利用，加速微生物量磷的周转，从而强化菌丝获取土壤磷的能力；（5）证明菌丝际解磷细菌群落组成显著受到磷酸盐形态、AM真菌种类和宿主植物种类的影响。