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

有关菌根圈微生物种群变化的证据已有报道，但调控这些变化的机制及其对植物健康的影响尚不清楚。丛枝菌根真菌（AMF）与陆地植物的共同进化至少有4亿年的密切关系，大多数植物物种都与这些真菌共生体密切相关，以适应环境。AMF直接影响根环境中植物的营养代谢和光合产物的释放，从而影响根际微生物群落。AM真菌是根际微生物群落的关键因子，有助于使根际微生物群落更加复杂和稳定，降低植物土传病原体的影响。更好地了解AM系统中的微生物动力学将有利于在园艺和农业系统中使用或操纵AM共生，减少化学物质的使用来控制根病。本研究计划的总体目标是了解AM真菌如何影响根际微生物群落并降低寄主植物的致病压力。具体目标是：1)分析田间镰刀菌、AM真菌和细菌群落与植物健康的功能关系；2)分析土壤微观环境下AM根际真菌-镰刀菌相互作用的种内变异和空间变异；3)表征AMF菌丝体与丝球菌的物理相互作用，以及生物膜形成群落在生物防治中的作用。各种分子、生物化学、微生物学和显微方法将用于测试AM真菌和细菌群落对镰刀菌群落结构和毒力的影响。该研究项目将为菌根圈微生物竞争相互作用的机制和菌根植物较低的疾病发展提供新的见解，显著提高我们在可持续农业方法中管理这种共生关系的能力。

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.