Arbuscular mycorrhizal fungi (AMF) form mutualistic symbiosis with roots of the majority of terrestrial plants. They are ceonocytic, known to harbour genetically different nuclei. However, the dynamic and maintenance of this genetic diversity are unknown. We have recently found two important processes that are likely to play a role in AMF: a) single spores do not necessarily inherit the same genetic material due to unequal segregation of nuclei during spore formation; b) mixing of nuclei between different individuals can occurs through genetic exchange. Under which circumstances these mechanisms could play a role in the maintenance of genetic diversity has been poorly studied and their occurrence in other AMF populations and species is unknown. Recent investigations suggest that environmental heterogeneity could be a process for the maintenance of genetic diversity and needs further investigations. Additionally, studying how plants respond to the dynamic of AMF genetic structure could allow us to understand how plant and fungi co-evolve. Finally, an important point would be to know whether local adaptation, segregation and genetic exchange could explain the genetic structure of AMF populations in the field. The three objectives of the proposed project will be to 1) test the effect of environmental heterogeneity on AMF genetic structure; 2) determine whether segregation and genetic exchange occur in other AMF populations and species; 3) compare our results with field data. It appears clear that understanding the dynamic and the maintenance of genetic diversity of AMF is essential for understanding the ecological importance of this very common symbiosis, for its application in agriculture and environmental management, and for understanding how organisms evolve and coevolve over long periods of time in a mutualistic environment.
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