Conspecificity of DAOM 197198, the model arbuscular mycorrhizal fungus, with Glomus irregulare: molecular evidence with three protein-encoding genes

Ribosomal nuclear genes are routinely utilized in the molecular identification of fungi. The variation in the multiple copies of these genes within each Glomeromycota strain and species reduces their usefulness for molecular characterization of arbuscular mycorrhizal fungi. To explore the potential of molecular tools for the identification of Glomus species, a multi-gene analysis approach was undertaken. Three protein- encoding genes were tested, namely elogation factor 1-α (765 bp), V-[H.sup.+]-ATPase VHA5 (1468 bp), and F0F1-ATPase β-subunit (621 bp). The latter is newly reported for the Glomeromycetes. Eleven species, including the type-specimen of Glomus irregulare Blaszk., Wubet, Renker & Buscot, a reference strain of G. intraradices N.C. Sehenck & G.S. Sm. (DAOM 225240), and five strains of Glomus sp. formerly identified as G, intraradices, were analysed. These genes did not show polymorphisms within strains, and results indicated a close relationship between molecular identification and morphological characterization. Species with closely related spore morphological features, G. aggregatum N.C. Schenck & G.S. Sm., G. diaphanum Morton & Walker, G. irregulare. and Glomus sp. DAOM 197198, showed more than 99% nucleotide similarity, while the morphologically distinct species, G. cerebriforme McGee, G. clarum T.H. Nicolson & N.C. Schenck, G. daroideum N.C. Schenck & G.S. Sm.. G. custos C. Cano & Dalpe. G. mosseae (T.H. Nicolson & Geld.) Gerd. & Trappe, and G. proliferum Dalpe & Declerck, showed less than 97% similarity for at least one gene. A 100% molecular similarity for all three genes was found between G. irregulare and Glomus sp. DAOM 197198. confirming the new identity of the model arbuscular mycorrhizal fungus. Similarity thresholds for identification by DNA sequencing are discussed. Key words: F0F1-ATPase β-subunit, V-[H.sup.+]-ATPase. VHA5, elongation factor 1-α, rDNA ITS. Glomus, molecular identification. DNA barcode. Les genes nucleaires ribosomiques sont couramment utilises pour l'identification moleculaire des champignons. Pour chaque espece de Glomeromycota, on retrouve plusieurs copies de ces genes el leur variation reduil considerablement leur efficacile. Une approche multigenique a ete envisagee pour developper des outils moleculaires applicables a l'identification des especes du genre Glomus. Trois genes codants sont vises ; facteur d'elongation 1-α (765 bp), V-[H.sup.+]-ATP synthase (VHA5) (1468 bp) et F0F1-ATP synthase sous-unite β (621 bp), ce dernier d'usage inedit chez les Glomeromycetes. Onze especes incluant le specimen-type de Glomus irregulare Blaszk., Wubet, Renker & Buscot, une souche originate de G. intraradices N.C. Schenck & G.S. Sm. (DAOM 225240) et cinq souches de Glomus sp. jusque-la identifiees au G intraradices out ete analysees en fonction de ces genes. Aucun polymorphisme genique intraspecifique n'a ete releve et les resultats montrent une relation directe entre l'identification moleculaire et la description morphologique. Les especes aux morphologies sporales apparentees, soit G. aggregatum N.C. Schenck & G.S. Sm., G diaphanum Morton & Walker, G. irregulare et Glomus sp. DAOM 197198 out montre plus de 99 % de similitude nucleotidique, tandis que les especes morphologiquement distinctes, soit G. cerebriforme McGee, G. clarum T.H. Nicolson & N.C. Schenck, G. claroideum N.C. Schenck & G.S. Sm., G. custos C, Cano & Dalpe, G, mosseae (T.H. Nicolson & Gerd.) Gerd. & Trappe et G. proliferum Dalpe & Declerck out montre moins de 97 % de similitude nucleotidique pour au moins un gene. Un poinlage parfait de 100 % de similitude moleculaire a ete observe entre G. irregulare et Glomus sp. DAOM 197198, confirmant la nouvelle identite du champignon mycorhizien arbusculaire modele. Les seuils de comparaison pour l'identification par sequencage d'ADN sont analyses. Mots-cles: F0F1-ATP synthase sous-unite β, V-[H.sup.+]-ATP synthase, VHA5, facteur d'elongation 1-α, ADNr ITS, Glomus, identification moleculaire, code a barres a ADN.
[Traduit par la Redaction] Introduction The search for efficient molecular markers for the detection and identification of arbuscular mycorrhizal (AM) fungi has been under way for many years, and attempts [...]