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Abstract: This report presents the first survey and analysis of the arbuscular mycorrhizal fungi community associated with Ammophila breviligulata Fernald (American beachgrass), of the Magdalen Islands archipelago, Quebec. Of the [...]

To investigate the influence of arbuscular mycorrhizal fungi (AMF) on biomass and root morphology, a greenhouse experiment was conducted using three elite strawberry (Fragaria X ananassa Duch.) cultivars ('Kent', 'Jewel', and 'Saint-Pierre'). They were subjected to three NaCl levels (0, 30, and 60 mmol/L) and were inoculated and noninoculated (control) with AMF Glomus irregulare. The presence of AMF significantly changed root morphology and increased root-length percentages of medium (0.5 mm < root diameter φ [less than or equal to] 1.5 mm) and coarse (4 > 1.5 mm) roots, shoot and root tissue biomass, root to shoot ratio (R/S ratio), and specific root length (SRL), regardless of cultivar and salinity. In contrast, salt alone changed root morphology and decreased shoot and root tissue biomass, R/S ratio, and SRL. The AMF colonization rates were reduced linearly and significantly with increasing salinity levels. Cultivars responded differently to AMF than to salt stress. 'Saint-Pierre' seemed to be the most tolerant cultivar to salinity, while 'Kent' was the most sensitive. Consequently, AMF symbiosis highly enhanced salt tolerance of strawberry plants, which confirmed the potential use of mycorrhizal biotechnology in sustainable horticulture in arid areas. Key words: arbuscular mycorrhizae, arid soil, salinity, strawberry, stress. Afin d'examiner l'influence des champignons mycorhiziens arbusculaires (CMA) sur la biomasse et la morphologie des racines, les auteurs ont conduit une experience en serres, en utilisant trois cultivars elites de fraisier (Fragaria X ananassa Duch.) ('Kent', 'Jewel',et 'St-Pierre'). Ils les ont soumis a trois concentrations de NaCl (0, 30, et 60 mmol/L), avec ou sans (temoin) inoculation, avec le CMA Glomus irregulare. La presence du CMA a modifie significativement la morphologie racinaire et a augmente les pourcentages des longueurs des racines moyennes (0,5 mm < diametre racinaire φ [less than or equal to] 1,5 mm) et grosses (φ >1,5 mm), la biomasse des tissus caulinaires et racinaires, le rapport racine tige (rapport R/S) et la longueur specifique des racines (LSR), independamment du cultivar ou de la salinite. Au contraire, le sel pris isolement a egalement modifie la morphologie racinaire et diminue la biomasse des tissus caulinaires et racinaires, le rapport R/S et la LSR. L'augmentation de la salinite a reduit lineairement et significativement la colonisation par le CMA. Le cultivar 'St-Pierre' apparait comme le plus tolerant a la salinite et le cv 'Kent' comme le plus sensible. On conclut que la symbiose CMA augmente fortement la tolerance a la salinite chez les plants de fraisiers, ce qui confirme le potentiel de la biotechnologie mycorhizienne pour l' horticulture en regions arides. Mots-cles : mycorhizes arbusculaires, sol aride, salinite, fraisier, stress. [Traduit par la Redaction], Introduction Plants are frequently exposed to adverse environmental conditions that have negative effects on development, productivity, and plant survival. Among environmental stresses, salinity is considered as the most important limiting [...]

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 [...]

The in-vitro culture of arbuscular mycorrhizal fungi on excised roots, especially when performed on bicompartmented Petri dishes, has proven to be an efficient system for the production of root-free fungal material. However, even after the contact between fungal hyphae and the excised roots in the proximal root compartment has occurred, up to several weeks may be required for the fungal runner hyphae to cross the median Petri dish wall and reach the distal fungal compartment. This delay is particularly long for the cultivation of slow-growing strains that usually colonize the substrate less aggressively. The delay is due to the difficulty the runner hyphae have in crossing the median Petri dish wall that separates compartments. To facilitate the passage of the fungus across the median wall, a 'paper bridge' system has been devised and tested with a number of arbuscular mycorrhizal fungal strains. This method substantially accelerated fungal propagation and simplified the manipulations necessary. The proposed paper-bridge system is described and its advantages discussed. Key words: arbuscular mycorrhizal fungi. Glomus, paper bridge, in-vitro culture. La culture in vitro des champignons mycorhiziens arbusculaires sur racines excisees, notamment en boites de Petri bi-compartintentees, constitue un systeme efficace de production axenique de champignon. Bien que le contact hyphe-racines s'effectue rapidement dans le compartiment racine, plusieurs semaines peuvent etre requises par les hyphes pour traverser dans la partie distale du systeme. Ce delai, particulierement long pour les souches a croissance lente et peu agressives, est du principalement a la difficulte pour les hyphes de traverser la cloison centrale qui separe les compartiments. Afin de remedier a celle difficulte un >> poni de papier << teste sur une diversite de souches myeorhiziennes s'est avere efficace pour accelerer la propagation fongique tout en simplifiant substantiellement les manipulations. Le systeme est decrit et ses avantages discutes. Mots-cles: champignons mycorhiziens arbusculaires. Glomus, pont papier, culture in vitro., Introduction Since 1975, when Hepper and Mosse first established cultures of arbuscular mycorrhizae (AM) on excised roots, tremendous improvements have been made with the use of Ri T-DNA transformed roots [...]