Arbuscular mycorrhizal fungi (AMF) are potential determinants of plant growth and plant diversity. AMF form complex belowground networks in the soil, where different isolates and different species are interacting. The mechanisms of competition and coexistence among AMF are poorly understood but can be very important to investigate plant benefits due to mycorrhizal symbioses. Here we made a greenhouse experiment, where we mainly tested the effect of relatedness between pairs of Glomus intraradices isolates co-inoculated in Allium porrum and Plantago lanceolata roots.
Results/Conclusions
The results clearly show that when the genetic distance between the co-existing isolate increase, this lead to a reduced plant growth. We also show that this pattern is unlikely to be explained by the amount of total fungal colonization in plant roots. However it is probably due to fungal intra-specific competition, as increasing genetic distance between the co-existing isolates lead to a strong disequilibrium in the frequency of each isolate inside plant roots. These unexpected results are counteracting the theory claiming that increasing AMF diversity will enhance plant productivity. To conclude, we are convinced that relatedness should be taken into account for any investigation of the interaction outcome in AMF and their effects on plant ecology.