(Speg.) Trappe & Gerd.
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Sporocarps (SEM) |
In PVLG |
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SPORES occurring singly in the soil in groups or sporocarps containing from 2 to 28 spore-groups. A single spore-group consists of 3 to 13 radially arranged and tightly adherent spores developed from a thick-walled, inflated hypha.
Sporocarps pale yellow (3A4) to brown (6E8); ovoid; 390-650 x 420-720 µm; to prolate; 190-270 x 290-380 µm; with or without a peridium.
Peridium hyaline to golden yellow (5B7); 10-70 µm thick; composed of thin-walled, interwoven hyphae, usually present only on a part of a sporocarp.
Spores pale yellow (3A4) to yellowish brown (5B7); globose to subglobose; (20.0-)47.0(-60.0) µm diam; or ovoid to prolate; 30-35 x 40-65 µm; with a single subtending hypha; spores frequently surrounded by branched and convoluted hyphae.
SUBCELLULAR STRUCTURE OF SPORES of one wall composed of two layers (swl1 and 2).
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In PVLG |
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Layer 1 evanescent, smooth, hyaline, (0.5-)0.8(-1.0) µm thick before disintegration, closely attached to layer 2.
Layer 2 laminate, pale yellow (3A4) to yellowish brown (5B7), (2.7-)3.9(-4.9) µm thick.
Layers 1 and 2 do not stain in Melzer’s reagent.
SUBTENDING HYPHA pale yellow (3A4) to yellowish brown (5B7); straight to recurvate; funnel-shaped, sometimes cylindrical or constricted; (6.1-)7.9(-9.3) µm wide at the spore base.
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In PVLG |
Wall of subtending hypha pale yellow (3A4) to yellowish brown (5B7); (2.2-)2.7(-3.4) µm thick; composed of two layers (shwl1 and 2), continuous with spore wall layers 1 and 2.Pore (0.5-)0.9(-1.2) µm wide, occluded by a septum, ca. 0.5-1.0 µm wide, continuous with the innermost lamina of spore wall layer 2, and occasionally by thickening of spore wall layer 2.
GERMINATION. Not observed.
MYCORRHIZAE. The ability of Gl. fuegianum to form mycorrhizae has not been experimentally confirmed so far. The type specimen of Gl. fuegianum has been found under moss (Pegler et al. 1993). Although Godfrey (1957) found this fungus under Taxus baccata L., the other reports from the United Kingdom informed of the occurrence of Gl. fuegianum associated with above-ground plant parts, including living or dead culms of Eriophorum angustifolium Honck., Molinia caerulea (L.) Moench, Nardus stricta L., Polytrichum and Sphagnum, as well as with rootstock of Juncus effusus L. and wet debris of a Molinia sp.
In Poland, Gl. fuegianum has been found in the field among vesicular-arbuscular mycorrhizal roots of Juniperus communis L. (Blaszkowski et al. 1998). Although Gl. fuegianum formed new spore-groups in trap cultures with Sorghum vulgare Pers., this fungus failed to sporulate in one-species pot cultures with this plant. The inability of arbuscular mycorrhizal fungi living in trap cultures to sporulate in single-species pot cultures probably results from the especially high selective nature of the latter ones, as Koske et al. (1997) and Koske (pers. comm.) suggested. The factor most limiting establishment of mycorrhizae in single-species pot cultures seems to be the lack of microflora of the soil from which a given fungus originated. Soil microorganisms have been demonstrated to hasten mycorrhizal fungus spore germination (Azcon-Aguilar et al. 1986) and root colonization (Azcon-Aguilar and Barea 1985).
DISTRIBUTION. In Poland, Gl. fuegianum has been found only in three soil samples collected from the root zone of J. communis growing in the inland dunes of the Kampinos National Park (52o18'N, 20o46'E; (Blaszkowski et al. 1998).
Glomus fuegianum has originally been found in Argentina (Pegler et al. 1993). However, most records of of this fungus come from the United Kingdom (Godfrey 1957; Pegler et al. 1993) where it was considered to be rather widespread. Additionally, Gl. fuegianum has been found in New Zealand (Hall 1977) and Australia (McGee and Trappe 2002). However, the finding of this fungus in only three of over 2500 soil samples collected in different regions of Europe, Africa, Asia, and the U.S.A. (Blaszkowski, pers. observ.) indicates Gl. fuegianum to be an extremely rarely occurring soil fungus in the world.
NOTES. The most closely related arbuscular mycorrhizal fungi producing spores similar in appearance and arranged in structures resembling the spore groups of Gl. fuegianum are Gl. rubiforme (Gerd. & Trappe) R.T. Almeida & N.C. Schenck and Gl. sinuosum (Gerd. & B.K. Bakshi) R.T. Almeida & N.C. Schenck (Almeida and Schenck 1990; Wu 1993a, b). Although both Gl. fuegianum and Gl. rubiforme form spores from a thick-walled, inflated hypha, the latter species lacks the hyphal mantle. Glomus sinuosum spores are mantled by sinuous hyphae reminiscent of those present in Gl. fuegianum, but the spores of Gl. sinuosum originate from a mass of interwoven hyphae, not from an inflated hypha as Gl. fuegianum.
REFERENCES
Almeida R. T., Schenck N. C. 1990. A revision of the genus Sclerocystis (Glomaceae, Glomales). Mycologia 82, 703-714.
Azcon-Aguilar C., Barea J. M. 1985. Effect of soil microorganisms on formation of vesicular-arbuscular mycorrhizas. Trans. Brit. Mycol. Soc. 84, 536-537.
Azcon-Aguilar C., Diaz-Rodriguez R. M., Barea J. M. 1986. Effect of soil microorganisms on spore germination and growth of the vesicular-arbuscular mycorrhizal fungus Glomus mosseae. Trans. Brit. Mycol. Soc. 86, 337-340.
Blaszkowski J., Madej T., Tadych M. 1998. Entrophospora baltica sp. nov. and Glomus fuegianum, two species in the Glomales from Poland. Mycotaxon 68, 165-184.
Godfrey R. M. 1957. Studies of British species of Endogone. I. Morphology and taxonomy. Trans. Br. Mycol. Soc. 40, 117-135.
Hall I. R. 1977. Species and mycorrhizal infections of New Zealand Endogonaceae. Trans. Br. Mycol. Soc. 68, 341-356.
Koske R. E., Gemma J. N., Jackson N. 1997. Mycorrhizal fungi associated with three species of turfgrass. Can. J. Bot. 75, 320-332.
McGee P. A., Trappe J. M. 2002. The Australian zygomycetous mycorrhizal fungi. II. Further Australian sporocarpic Glomaceae. Aust. Sys. Bot. 15, 115-124.
Pegler D. N., Spooner B. M., Young T. W. K. 1993. British truffles. A revision of British hypogeous fungi. Royal Botanic Gardens, Kew. 216 pp. + 26 plates.
Wu C.-G. 1993a. Glomales of Taiwan: III. A comparative study of spore ontogeny in Sclerocystis (Glomaceae, Glomales). Mycotaxon 47, 25-39.
Wu C.-G. 1993b. Glomales of Taiwan: IV. A monograph of Sclerocystis (Glomaceae). Mycotaxon 49, 327-349.
