Elucidating the genetic structure of populations of arbuscular mycorrhizal fungi (Glomeromycota)

Arbuscular mycorrhizal fungi are ubiquitous mutualistic associates of plants. Only relatively recently it has become possible to study the population biology of some species of these fungi, which are placed in the phylum Glomeromycota. Some species-level taxa of the Glomeromycota seem to be extremely widespread. In particular, the model organism Rhizophagus irregularis (formerly known as Glomus intraradices) has been found across an extremely wide range of habitats and succession stages on different continents using molecular identification approaches. We have used regions of the mitochondrially-encoded rDNA as molecular markers to resolve the intraspecies structure of this species and found a high diversity of mitochondrial haplotypes among isolates from all over the world. These markers for the first time also allow to genotype glomeromycotan fungi directly within colonized roots. Using this approach, we found a surprisingly high degree of genetic differentiation of G. intraradices among arable sites in Switzerland. Grasslands showed a completely different set of haplotypes compared to arable sites. Mitochondrial rDNA also proved to be a useful marker to verify inoculation success in the context of the application of arbuscular mycorrhizal fungi in biotechnology, which might contribute to sustainable land use in the future. These findings will be presented in the context of other recent work addressing the structure of glomeromycotan populations