C.M. Pfeiff., C. Walker & Bloos emend. L.J. Kenn., J.C. Stutz & J.B. Morton
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SPORES borne singly in the soil; hyaline to pale yellow (4A3); globose to subglobose; (75-)86(-110) µm diam; with a single subtending hypha.
SUBCELLULAR STRUCTURE OF SPORES consists of one wall with three layers (swl1-3).
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In PVLG+Melzer's reagent |
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Layer 1 granular or mucilaginous in young spores, becoming more compact with age, hyaline to pale yellow (4A3), 0.5-1.0 µm thick, inseparable from layer 2, usually present even in older spores.
Layer 2 permanent, flexible, hyaline to pale yellow (4A3), (0.9-)1.0(-1.2) µm thick, frequently ballooning in lactic acid-based mountants.
Layer 3 laminate, hyaline, smooth, (1.6-)4.5(-5.4) µm thick, composed of very thin, <0.5 µm thick, tightly adherent sublayers, sometimes separating in vigorously crushed spores.
None of the spore wall layers stains in Melzer’s reagent.
Most juvenile spores hyaline, with two-layered wall, each ca. 0.5 µm thick.
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Spores from Dr. C. Walker
in PVLG |
Spores from Dr. C. Walker
in PVLG+Melzer's reagent |
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In PVLG+Melzer's
reagent
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Wall of subtending hypha hyaline to pale yellow (4A3); (0.9-)1.0(-1.3) µm thick at the spore base; composed of two layers (shwl1 and 2), continuous with spore wall layers 1 and 2; layer 3 of spore wall extends along layer 1 of subtending hyphal wall only very closely at the spore base.
Pore 2.9-7.6 µm diam, occluded by a thin septum or a plug.
GERMINATION. Not observed.
MYCORRHIZAE. Many attempts to establish mycorrhizae of Gl. spurcum in one-species pot cultures with Plantago lanceolata L. as the plant host failed. According to Morton (2000) and Pfeiffer et al. (1996), the mycorrhizae of Gl. spurcum consisted of arbuscules and intraradical hyphae staining with variable intensity (from almost invisible to dark). No vesicles were found.
DISTRIBUTION. In Poland, spores of Gl. spurcum were first found in three trap cultures with root-rhizosphere soils of Beta vulgaris L. and Triticum aestivum L. cultivated in Drzemin (53º15’N, 14º39’E), Kolbacz (53o18’N, 14o49’E), and Stobno (53º26’N, 14º23’E) in the Western Pomerania voivodeship (Błaszkowski et al. 2003; Iwaniuk and Błaszkowski, unpubl.). Subsequently, this fungus was revealed in 40 trap cultures containing root-rhizosphere mixtures taken from under Corynephorus canescens (L.) P. Beuv., Elymus arenarius L., Eryngium maritimum L., Festuca rubra L., Phragmites australis (Cav.) Trin. ex Steud., Rubus fructicosus L. nom. Ambig., and Salix sp. colonizing maritime dunes adjacent to Darlówko (54º26’N, 16º23’E) adjacent to the Baltic Sea.
Glomus spurcum has originally been discovered in a greenhouse bed of sand used for propagation of various ornamental plants cultivated in Arizona (Pfeiffer et al. 1996). This fungus has also been found in maritime dunes of Mexico (Pfeiffer et al. 1996), Hawaii (Koske and Gemma 1996), San Miguel Island, California (Koske, pers. inform.), as well as in different other natural ecosystems of North America, Cuba and Namibia, Africa (Kennedy et al. 1999; Stutz and Morton 1996; Stutz et al. 2000).
NOTES. The layer 1 of spores of Gl. spurcum characterized here has been not included in the spore wall structure of this fungus in any earlier its description (Błaszkowski et al. 2003; Kennedy et al. 1999; Pfeiffer et al. 1996), although the presence of this structure has been mentioned. Pfeiffer et al. (1996) considered it to be a mucilaginous material formed by overlapping plate-like structures when examined with a scanning electron microscope. According to Kennedy et al. (1999), it rather is an accumulation of organic matter, because it does not stain in Melzer's reagent as a typical mucilaginous layer.
The wall layer 1 of Gl. spurcum spores examined by the author of this website occurred in almost all the specimens of this fungus coming from both Poland and those received from Dr. C. Walker, U. K.
The fungal species most similar morphologically to Gl. spurcum are Gl. albidum C. Walker & L.H. Rhodes, Gl. eburneum L.J. Kenn. et al., Gl. gibbosum Blaszk., Gl. viscosum Nicol., and Paraglomus occultum (C. Walker) J.B. Morton & D. Redecker. These species produce hyaline to light-coloured spores of a similar size when observed under a dissecting microscope.
However, Gl. albidum forms spores with a wall composed of an outer evanescent layer and an inner laminate layer (Walker and Rhodes 1981). Both layers have a similar thickness. In contrast, the outer layer of Gl. spurcum spores is permanent and much thinner than the inner laminate layer. Young spores of Gl. albidum stain pink to orange in Melzer’s reagent, whereas those of Gl. spurcum are non-reactive in this reagent.
The property distinguishing Gl. eburneum is the formation of ovoid to tear-drop shaped spores (Kennedy et al. 1999). Spores of Gl. spurcum consistently are globose. However, the main differences between these fungi reside in the properties of spore wall layers, which are evident only in heavily crushed spores. The outer layer of Gl. eburneum spores remains adherent to the inner laminate one, and the permanent layer 1 and the laminate layer 2 of the Gl. spurcum spore wall usually completely separate from each other. Additionally, most vigorously crushed spores of Gl. spurcum are devoid of subtending hypha that along with layer 1 of spore wall separates from the laminate spore wall layer forming too weak structural support of the hypha.
Layers 2 and 3 of spore wall of Gl. gibbosum are similar to layers 1 and 2 of spore wall of Gl. spurcum (Błaszkowski 1997). However, in the former species, layer 2 is still associated with an outer evanescent layer, and the laminate layer 3 surrounds a flexible, colourless innermost layer that is lacking in the latter fungus.
Spores of Gl. viscosum occur in loose aggregates (Walker et al. 1995) rather than singly in the soil as those of Gl. spurcum. The spore wall of Gl. viscosum consists of three layers (Morton 2000) with the outermost one exuding a mucigel-like substance (this phenomenon does not occur in Gl. spurcum). Glomus viscosum also has a persistent subtending hypha (vs. it usually is absent in crushed spores of Gl. spurcum).
Spores of P. occultum remain hyaline throughout their life cycle (Morton and Redecker 2001; Walker 1982). In contrast, mature spores of Gl. spurcum usually are pale yellow. Additionally, the wall of P. occultum spores consists of three layers of equal thickness, whereas the total thickness of the wall layers 1 and 2 of Gl. spurcum spores is much lower than the thickness of the innermost layer 3. Finally, the innermost layer of P. occultum is a permanent structure lacking sublayers (vs. a laminate layer in Gl. spurcum).
REFERENCES
Błaszkowski J. 1997. Glomus gibbosum, a new species from Poland. Mycologia 89, 339-345.
Błaszkowski J., Adamska I., Czerniawska B. 2003. Glomus claroideum and G. spurcum, arbuscular mycorrhizal fungi (Glomeromycota) new for Poland and Europe, respectively. Acta Soc. Bot. Pol. 72, 149-156.
Kennedy L. J., Stutz J. C., Morton J. B. 1999. Glomus eburneum and G. luteum, two new species of arbuscular mycorrhizal fungi, with emendation of G. spurcum. Mycologia 91, 1083-1093.
Koske R. E., Gemma J. N. 1996. Arbuscular mycorrhizal fungi in Hawaiian sand dunes: Island of Kaua’i. Pacific Sci. 50, 36-45.
Morton J. B. 2000. International Culture Collection of Arbuscular and Vesicular-Arbuscular Mycorrhizal Fungi. West Virginia University.
Morton J. B., Redecker D. 2001. Two families of Glomales, Archaeosporaceae and Paraglomaceae, with two new genera Archaeospora and Paraglomus, based on concordant molecular and morphological characters. Mycologia 93, 181-195.
Pfeiffer C. M., Walker C., Bloss H. E. 1996. Glomus spurcum: a new endomycorrhizal fungus from Arizona. Mycotaxon 59, 373-382.
Stutz J. C., Morton J. B. 1996. Successive pot cultures reveal high species richness of arbuscular mycorrhizal fungi in arid ecosystems. Can. J. Bot. 74, 1883-1889.
Stutz J. C., Copeman R., Martin C. A., Morton J. B. 2000. Patterns of species composition and distribution of arbuscular mycorrhizal fungi in arid regions of southwestern North America and Namibia, Africa. Can. J. Bot. 78, 237-245.
Walker C. 1982. Species in the Endogonaceae: a new species (Glomus occultum) and a new combination (Glomus geosporum). Mycotaxon 15, 49-61.
Walker C., Rhodes L. H. 1981. Glomus albidus: a new species in the Endogonaceae. Mycotaxon 12, 509-514.
Walker C., Giovannetti M., Avio L., Citernesi A. S., Nicolson T. H. 1995. A new fungal species forming arbuscular mycorrhizas: Glomus viscosum. Mycol. Res. 99, 1500-1506.
