THE RESPONSE OF ASTER AMELLUS (ASTERACEAE) TO MYCORRHIZA DEPENDS ON THE ORIGINS OF BOTH THE SOIL AND THE FUNGI

. Premise of study: Previous studies testing pairwise interactions between plants, arbuscular mycorrhizal fungi (AMF) and soil have shown that the effectiveness of such interactions depends on the origins of the plants, soil, and AMF. Surprisingly, no study has yet looked at the three-way interaction between plants, soil, and AMF originating from the same and from different sites. Such knowledge could elucidate the determinants of local adaptations of plants and thus might help in various revegetation attempts. . Methods: Six populations of the obligately mycorrhizal plant species Aster amellus from two isolated regions were combined with the soil and the AMF ecotype from their sites and plant growth were monitored over 16 months. . Key results: For each combination of soil and native AMF, plants grown with their native AMF in their native soil had higher aboveground biomass, invested more to aboveground biomass and had higher numbers of flower heads than the other plants. The specificity of the relationship among plant populations, AMF, and soil was also observed for percentage of root colonization. . Conclusions: The study extends our knowledge of the specific interaction between plants and AMF by demonstrating that the positive effect of native AMF occurs only when the plants are also grown in their native soil. Thus, when attempting to facilitate plant growth, we need to consider the origin of the plants, the soil, and the AMF, because all three components are adapted to each other.