Interaction between plant root and arbuscular mycorrhiza (AM) is a crucial symbiosis in nature and present in almost all crops. In addressing plant responses to stress, this proposal shifts the focus from the host to the symbiotic unit. By recognizing symbiosis to be a major player in evolution, the interplay is valued between the adaptive regulation of host and symbionts metabolisms.Using wild carrots, their AM community and the alternatieve oxidase (AOX) candidate gene, the researcher will address the prediction that AOX gene polymorphisms are drivers in interlinked plant and AM fungi evolution. This project studies - for the first time - the interaction between plant and AM in natural ecosystems using a crucial candidate marker, followed by experiments exploring driving effects of evolution. The research will lead to better understanding of evolutionary processes that shape the composition of the symbiosis and of the benefit of diversity to crop productivity. The approach is interdisciplinary: physiology, ecology and evolutionary genetic methodologies. There is high commercial interest in appropriate breeding strategies based on efficient genotype-mycorrhiza as they can promote, a.o., a more sustainable use of phosphorus in crops and minimize associated biodiversity losses, and mitigate the impacts of global climate change on agricultural and native plant communities.A similar proposal was previously submitted in 2011-CIG which achieved overall high scores. The present proposal addresses the referees’ comments, which mainly concerned better explanation of the methodologies and their feasibility.The researcher’s profile closely matches the project needs, and her independent thinking and entrepreneurship, together with the high academic profile of the host Marie-Curie chair, provide a strong foundation for successful implementation of this project and long-term integration of the researcher.