Rhizopogon kretzerae sp. nov.: the rare fungal symbiont in the tripartite system with Pterospora andromedea and Pinus strobus

The first species of Rhizopogon subgenus Amylopogon identified from eastern North America is described here as Rhizopogon kretzerae Grubisha, Dowie, & Mill. sp. nov. In nature, R. kretzerae has been identified only from DNA sequences of the nuclear ribosomal internal transcribed spacer region (ITS) from mycorrhizal roots of Pinus strobus L. and Pterospora andromedea Nutt. Phylogenetic analyses and nucleotide divergence estimates of Rhizopogon ITS sequences from Pterospora roots from Quebec, Michigan, New York, and New Hampshire combined with ITS sequences of Rhizopogon subgenus Amylopogon species type collections suggest R. kretzerae is a sister-group to Rhizopogon salebrosus A.H. Sm. An absence of shared mutations, two informative sequence gaps, and 12 fixed nucleotide differences differentiate R. kretzerae and R. salebrosus. Furthermore, ITS sequences of 40 Pterospora root samples from five populations in the province of Quebec provided the first record of the distribution of R. kretzerae, a potentially rare to endangered species, in eastern Canada. Key words: Rhizopogon kretzerae, mycoheterotrophy, Pterospora andromedea, endangered species, rare fungi. La premiere espece de Rhizopogon sous-genre Amylopogon identifiee dans l'est de l'Amerique du Nord est decrite ici comme Rhizopogon kretzerae Grubisha, Dowie, & Mill. sp. nov. Dans la nature, R. kretzerae n'a ete identifie que par les sequences d'ADN de la region de l'espaceur interne transcrit (ITS) nucleaire ribosomal des racines mycorhiziennes de Pinus strobus L. et Pterospora andromedea Nutt. Les analyses phylogenetiques et l'estimation des divergences nucleotidiques des sequences de l'ITS des racines de Pterospora du Quebec, du Michigan, de l'etat de New-York et du New-Hampshire, combinees aux sequences de l'ITS de collections types de l'espece Rhizopogon sous-genre Amylopogon suggerent que R. kretzerae est un groupe-sreur de Rhizopogon salebrosus A.H. Sm. En absence de mutations partagees, deux lacunes en sequences informatives et 12 differences nucleotidiques fixes differencient R. kretzerae et R. salebrosus. De plus, les sequences des ITS de 40 echantillons de racines de Pterospora de cinq populations de la province de Quebec fournissent la premiere compilation de la distribution de R. kretzerae, une espece rare potentiellement menacee, dans l'est du Canada. [Traduit par la Redaction] Mots-cles: Rhizopogon kretzerae, mycoheterotrophie, Pterospora andromedea, especes menacees, champignons rares.
Introduction Mycoheterotrophic plants rely on carbon transferred through a mycorrhizal fungus from a photosynthetic host plant. Pterospora (Monotropoideae, Ericaceae) is a monotypic mycoheterotrophic genus composed of a single species, Pterospora [...]