High genetic diversity in arbuscular mycorrhizal fungi: evidence for recombination events

Abstract

The genetic diversity of spores of two indigenous species of Glomus isolated from three soils of a long-term field experiment amended by different quantities of sewage sludges has been evaluated. Three populations of spores of Glomus claroideum (W2537) and three populations of spores of Glomus DAOM 225952 (W2538) were analysed using a microsatellite primer and aliquots of genomic DNA were obtained from single spores (Inter Simple Sequence Repeat (ISSR) fingerprints). 39 polymorphic bands were found for G. claroideum, and 43 in Glomus DAOM 225952. The intraspecific diversity was high, ranging from 22 to 33 different electrophoretic types for G. claroideum, and 15-27 for Glomus DAOM 225952 depending on the population. Resampling experiments showed that the number of polymorphic bands was sufficient to score all multilocus profiles in the populations and to describe the clonality structure within populations. On average, one multilocus profile was represented by about four spores whatever the population and the species. Partitioning of the within-species phenotypic variance showed that more than 92% of the variation was found within populations, while the among-population variance component accounted for less than 8%, even though it was statistically different from 0. This result is confirmed by the fact that only few multilocus profiles were shared by two populations of G. claroideum, and none by populations of Glomus DAOM 225952. In addition to the high level of diversity observed within populations, linkage disequilibria analyses and association indices calculated across loci indicates that reproduction cannot be solely clonal. Recombination or recombination-like events are likely to occur in these arbuscular mycorrhizal fungi. An 'epidemic' population structure was found for both fungal species in the soil that had received high amounts of sewage sludge.

Arbuscular mycorrhizal fungal diversity in perennial pastures; responses to long-term lime application

“…A recent study of AMF in acid soil also showed that only 24% of the AMF morphotypes present could be identified to species level, while most of them did not fit published descriptions (Cuenca and Lovera 2010). In addition, a single genetic locus will not give a clear cut-off between intra-species genetic variation, which may also cause branching when clustering these sequences in phylogenetic analysis (Morton 1995;Vandenkoornhuyse et al 2001). In the current study, A. laevis and S. pellucida clustered in the Aca/Scu phylotype group although they showed high similarity with Acaulospora and Scutellospora species outside of this phylotype group in the BLAST search (Fig.…”

Population Genetics of Hirsutella rhossiliensis, a Dominant Parasite of Cyst Nematode Juveniles on a Continental Scale

“…The PrCP test measures whether two loci are compatible, and the ⌽ w test examines (56,57). In arbuscular mycorrhizal fungi, recombination or recombination-like events in addition to clonality have greatly contributed to genetic diversity (58). This study has demonstrated evidence of recombination among H. rhossiliensis strains, and recombination appears to be one of the factors shaping the evolution of H. rhossiliensis.…”

Genomics of Arbuscular Mycorrhizal Fungi

“…No such cell events have been observed in AM fungi. As anastomosis is a well-described process among Glomeromycota (den Bakker, Vankuren, Morton, & Pawlowska, 2010;Vandenkoornhuyse, Leyval, & Bonnin, 2001), a consensus was reached that AM fungi reproduce asexually, exchanging genes by hyphal fusion and forming asexual spores. However, genes have been found that are related either to meiosis or to mating with the so-called mating type (MAT) loci, responsible for cell identity and thus compatibility.…”