title: Significant genetic and phenotypic changes arising from clonal growth of a single spore of an arbuscular mycorrhizal fungus over multiple generations.
abstract: Arbuscular mycorrhizal fungi (AMF) are highly successful plant symbionts. They reproduce clonally producing multinucleate spores. It has been suggested that some AMF harbor genetically different nuclei. However, recent advances in sequencing the Glomus irregulare genome have indicated very low within-fungus polymorphism. We tested the null hypothesis that, with no genetic differences among nuclei, no significant genetic or phenotypic variation would occur among clonal single spore lines generated from one initial AMF spore. Furthermore, no additional variation would be expected in the following generations of single spore lines. Genetic diversity contained in one initial spore repeatedly gave rise to genetically different variants of the fungus with novel phenotypes. The genetic changes represented quantitative changes in allele frequencies, most probably as a result of changes in the frequency of genetic variation partitioned on different nuclei. The genetic and phenotypic variation is remarkable, given that it arose repeatedly from one clonal individual. Our results highlight the dynamic nature of AMF genetics. Even though within-fungus genetic variation is low, some is probably partitioned among nuclei and potentially causes changes in the phenotype. Our results are important for understanding AMF genetics, as well as for researchers and biotechnologists hoping to use AMF genetic diversity for the improvement of AMF inoculum.
authors.affiliation: Department of Ecology & Evolution, University of Lausanne, 1015, Lausanne, Switzerland.
authors.forename: Martine O
authors.initials: MO
authors.lastname: Ehinger
authors.affiliation: Department of Ecology & Evolution, University of Lausanne, 1015, Lausanne, Switzerland.|Plant Pathology, Institute of Integrative Biology, ETH Zürich, 8092, Zürich, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Croll
authors.affiliation: Department of Ecology & Evolution, University of Lausanne, 1015, Lausanne, Switzerland.|Irving K. Barber School of Arts and Sciences, University of British Columbia at Okanagan, Okanagan, Kelowna, BC, V1V 1V7 Canada.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Koch
authors.affiliation: Department of Ecology & Evolution, University of Lausanne, 1015, Lausanne, Switzerland.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Sanders
mesh_terms: D000483:Alleles; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics; D005787:Gene Frequency; D014644:Genetic Variation; D015726:Giant Cells / Q000378:metabolism; D040582:Inheritance Patterns / Q000235:genetics*; D038821:Mycorrhizae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010641:Phenotype; D013172:Spores, Fungal / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D013559:Symbiosis
chemical_list: D004271:DNA, Fungal