Communities and populations of sebacinoid basidiomycetes associated with the achlorophyllous orchid Neottia nidus-avis (L.) L.C.M. Rich. and neighbouring tree ectomycorrhizae

Authors

  • Marc-André Selosse,

    Corresponding author
    1. Institut de Systématique (IFR CNRS 1541), Muséum National d’Histoire Naturelle, 43 rue Cuvier, F-75005 Paris, France,
      M.-A. Selosse. Fax: +33 140793844; E-mail: ma.selosse@wanadoo.fr
    Search for more papers by this author
  • Michael WEIß,

    1. Lehrstuhl für Spezielle Botanik und Mykologie, Botanisches Institut, Universität Tübingen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany,
    Search for more papers by this author
  • Jean-Luc Jany,

    1. UR 349, Unité de recherches ‘Ecosystèmes forestiers’, Equipe de Microbiologie Forestière, INRA, Centre de Recherches Forestières de Nancy, F-54280 Champenoux, France
    Search for more papers by this author
  • Annie Tillier

    1. Institut de Systématique (IFR CNRS 1541), Muséum National d’Histoire Naturelle, 43 rue Cuvier, F-75005 Paris, France,
    Search for more papers by this author

M.-A. Selosse. Fax: +33 140793844; E-mail: ma.selosse@wanadoo.fr

Abstract

Several achlorophyllous orchids associate with ectomycorrhizal hymenomycetes deriving carbon from surrounding trees for the plant. However, this has not been shown for achlorophyllous orchids associating with species of Rhizoctonia, a complex of basal lineages of hymenomycetes that are the most common orchid partners. We analysed Neottia nidus-avis, an achlorophyllous orchid symbiotic with a Rhizoctonia, to identify its symbionts by internal transcribed spacer (ITS) sequencing. Analysis of 61 root systems from 23 French populations showed that N. nidus-avis associates highly specifically with a group of species of Sebacinaceae. Their diversity emphasizes the need for further investigations in the Sebacinaceae systematics. Sebacinoid ITS sequences were often identical within orchid populations and a trend to regional variation in symbionts was observed. Using ITS and intergenic spacer (IGS) polymorphism, we showed that each root system harboured a single species, but that several genets colonized it. However, no polymorphism of these markers was found among portions of each root: this is consistent with the putative mode of entry of the fungus, i.e. from the rhizome into roots but not repeatedly from the soil. In addition, ectomycorrhizae were always found within the N. nidus-avis root systems: 120 of the 144 ectomycorrhizae typed by ITS sequencing were colonized by a sebacinoid fungus identical in ITS sequence to the respective orchid symbiont (even for the IGS polymorphism in some cases). Because sebacinoids were demonstrated recently to be ectomycorrhizal, the orchid is likely to derive its resources from surrounding trees, a mycorrhizal cheating strategy similar to other myco-heterotrophic plants studied to date.

Ancillary