华南典型稻田湿地丛枝菌根真菌群落特征及其与水稻的碳磷交易动态

Arbuscular mycorrhizal fungi (AMF) are the most widespread and functionally important plant symbiotic microbes in terrestrial ecosystems, but our knowledge of their community structure in different wetland habitats and their nutrient interactions with their wetland hosts in these habitats is still largely unknown. Our previous study found that AMF were widely present in the paddy wetlands in South China. Further studies confirmed that phosphorus - carbon trade was taking place between AMF and their rice hosts even under waterlogging, implying that AMF could be of great significance in the nutrient cycling in paddy wetlands. In the proposed study, we plan to investigate the AMF symbiotic conditions, community structures and their main influencing factors in typical paddy wetlands in South China, using both the 454 pyrosequencing technology and the traditional research methods. In order to illustrate the dynamics of phosphorus - carbon trade of the AM symbiosis in paddy wetlands,we also plan to conduct greenhouse experiments to investigate (i) the conditions of phosphorus - carbon trade of AM symbiosis at various physiological stages of rice and (ii) the dynamics of phosphorus - carbon trade between AMF and their rice hosts under different waterlogging and phosphorus conditions.The present research project can not only improve our understanding of the AMF community characters and their influencing factors in wetland ecosystems, but also clarify the potential role of AMF in the carbon and phosphorus cycling in wetland ecosystems, thus providing new insights into the sustainable production of rice, and the establishment and protection of wetland ecosystems.

作为陆地生态系统中分布最广泛和最重要的植物共生微生物，丛枝菌根真菌（AMF）在湿地生境中的群落特征及其与湿地宿主的养分共生机制还所知甚少。本课题组近期发现AMF在华南地区的稻田湿地中广泛存在；预实验进一步证实水淹环境下AMF与水稻存在碳磷交易，暗示AMF对稻田湿地的养分流动具有重要影响。本课题拟结合焦磷酸测序和传统的AMF研究方法，系统研究华南典型稻田湿地中AMF在不同发育期水稻根内和根际土壤中的分布状况、群落特征以及影响AMF与水稻共生关系的关键因子。并通过模拟湿地环境的控制实验，进一步探究AMF与不同发育期水稻的碳磷交易动态，以及两者碳磷交易对湿地环境因子（淹水方式、淹水阶段、养分水平）的响应过程。项目的实施不仅能加深对湿地环境中AMF群落特征及其影响因子的理解，也将揭示AMF在湿地生态系统碳、磷流动和循环中的意义，进而为AMF应用于水稻清洁生产及湿地生态系统的保护与构建提供重要指导。

作为陆地生态系统中分布最广泛和最重要的植物共生微生物，丛枝菌根真菌（AMF）在湿地生境中的群落特征及其与湿地宿主的养分共生机制还所知甚少。本课题组前期发现AMF在华南典型的稻田湿地中广泛存在；预实验进一步证实水淹环境下AMF与水稻存在碳磷交易，暗示AMF对稻田湿地的养分流动具有重要影响。本课题结合分子生态和传统的AMF研究方法，系统研究了华南典型稻田湿地中AMF在不同发育期水稻根内和根际土壤中的分布状况、群落特征以及影响AMF与水稻共生关系的关键性因子。结果表明，在营养生长期（幼苗期、分蘖期）的水稻根内几乎没有AMF定殖，而在水稻的繁殖生长期（抽穗期、结实期）根内具有典型的菌根结构。我们从水稻根系和根际土壤中一共获得639条AMF序列，并将其归类到16个AMF种系型，其中12个属于Glomeraceae、1个属于Claroideoglomeraceae、2个属于Paraglomeraceae，还有1个未知种系型，证明稻田湿地中AMF多样性水平较高。不同稻田湿地中AMF种系型组成非常类似，而同一稻田的根系和根际土壤中AMF群落存在明显的差异。该调查研究表明，部分AMF种类能适应高投入、集中灌溉的生境条件。在此基础上，我们通过对湿地环境中AMF群落结构的细致解析及模拟湿地环境的控制实验，进一步探究了AMF与不同发育期水稻的“碳磷交易”以及该养分交易对湿地环境因子（淹水方式、养分水平）的动态响应过程。结果表明，AMF与湿地植物的养分互作明显依赖于宿主的生理特征及发育阶段，并受到淹水强度和养分水平的调控。遮阴（低碳）处理在一定程度上降低了水稻与AMF的碳磷交易水平，而低磷处理的调控效果并不明显。水分管理强烈影响水稻与AMF的碳磷交易水平：结合13C同位素示踪及分子生物学手段，我们首次获得在淹水环境下AMF与水稻进行“碳磷交易”的直接证据，并证实两者养分交易强烈受到淹水环境的抑制。项目的开展不仅深入了对湿地环境中AMF群落特征及其影响因子的理解，也揭示了AMF与湿地宿主的养分互惠机理，对将AMF应用于水稻清洁生产及湿地生态系统保护与构建具有重要的指导意义。