Impact of arbuscular mycorrhiza to soil microbial communities and biocontrol of soil-borne pathogens

有证据表明菌根圈中的微生物种群发生了变化，但调节这些变化的机制及其对植物健康的影响却知之甚少。丛枝菌根真菌(AMF)与陆地植物共同进化了至少400多年，大多数植物物种都与这些真菌共生体密切相关地适应环境。AMF直接影响根际环境中植物的营养代谢和光合作用产物的释放，从而影响根际微生物群落。AM真菌是根际的关键因子，有助于使根际微生物群落更加复杂和稳定，降低土传植物病原菌的影响。更好地了解AM系统中的微生物动力学将有利于AM共生在园艺和农业系统中的使用或操作，减少化学物质的使用来控制根部病害。本研究的总体目标是了解AM真菌如何影响根际微生物群落，降低寄主植物的致病压力。具体目标是：1)分析与田间植物健康相关的镰刀菌、AM真菌和细菌群落之间的功能关系；2)在受控土壤微宇宙中分析AM根际AM真菌-镰刀菌相互作用的种内和空间变异性；3)表征Hyphere细菌和AMF菌丝体之间的物理相互作用，以及生物膜形成群落在生物防治中的作用。将使用各种分子、生化、微生物学和显微方法来测试AM真菌和细菌群落对镰刀菌群落结构和毒力的影响。这项研究计划将为菌根圈微生物竞争相互作用和降低菌根植物疾病发展的机制提供新的见解，显著增强我们在可持续农业方法中管理这种共生的能力。

Evidences of microbial population shifts in the mycorrhizosphere have been reported but the mechanisms regulating these changes and their impact on plant health are poorly known. Arbuscular mycorrhizal fungi (AMF) have coevolved in intimate relationship with land plants for at least 400 M yr and most plant species are adapted to the environment in close relationship with these fungal symbionts. AMF directly influence the plant nutrition metabolism and the release of photosynthates in the root environment, hence the microbial community living in the rhizosphere. AM fungi are key-factors in the rhizosphere and would contribute to make more complex and stable the rhizosphere microbial community, lowering the impact of soilborne plant pathogens. A better knowledge of microbial dynamics in AM systems will favor the use or manipulation of the AM symbiosis in horticulture and agrosystems, lowering the use of chemicals to control root diseases. The general goal of this research program is to understand how the AM fungi influence the rhizosphere microbial communities and lower the pathogenic pressure on host plants. Specific goals are : 1) To analyze the functional relationships between Fusarium, AM fungi and bacterial communities as related with plant health in the field; 2) To analyze the intraspecific and spatial variability in the AMF-Fusarium interaction in the AM rhizosphere in controlled soil microcosms; and 3) To characterize the physical interaction between hyphosphere bacteria and AMF mycelium, and the role of biofilm-forming communities in biocontrol. Various molecular, biochemical, microbiological and microscopical approaches will be used to test the effects of AM fungal and bacterial communities on Fusarium community structure and virulence. This research program will provide novel insight in the mechanisms leading to microbial competitive interactions in the mycorrhizosphere and to the lower disease development in mycorrhizal plants, significantly enhancing our capability to manage this symbiosis in a sustainable agricultural approach.