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SPORES formed singly in the soil; yellow (4A8) to orange (5B8); globose to subglobose; (150-)189(-265) µm diam; sometimes ovoid; 145-170 x 170-220 µm; with a single subtending hypha.
SUBCELLULAR STRUCTURE OF SPORES of one wall with three layers (swl1-3).
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In PVLG |
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In PVLG+Melzer's reagent |
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Layer 1 evanescent, hyaline, (0.8-)1.3(-1.7) µm thick, usually absent in field-collected specimens.
Layer 2 laminate, yellow (4A8) to orange (5B8), (5.1-)9.8(-12.5) µm thick.
Layer 3 semirigid, pale yellow (4A4-8) to orange (5B8), (0.6-)1.1(-1.5) µm thick, ornamented with evenly distributed warts projecting inward from the inner surface of this layer; warts 0.8-1.7 µm high in a cross view, 0.5-0.7 µm diam in a plan view; this layer sometimes separates from layer 2 in vigorously crushed spores.
Layers 1-3 do not stain in Melzer’s reagent.
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In PVLG+Melzer's reagent |
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Wall of subtending hypha yellow (4A8) to orange (5B8); (4.8-)5.6(-6.9) µm thick at the spore base; composed of two layers (shwl1 and 2), continuous with spore wall layers 1 and 2; layer 1 continuing distally for up to 25 µm along the subtending hypha.
Pore closed by a curved septum, continuous with the innermost spore wall layer 3.
GERMINATION. A germ tube emerges from the lumen of the subtending hypha.
MYCORRHIZAE. In one-species cultures with Plantago lanceolata L. as the plant host, mycorrhizae of Gl. verruculosum consisted of arbuscules, vesicles, as well as intra- and extraradical hyphae staining moderately in 0.1% trypan blue. The arbuscules and vesicles occurred sparsely.
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In roots of P. lanceolata
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DISTRIBUTION. Glomus verruculosum has originally been described from spores isolated from the root zone of Epilobium hirsutum L. and Glyceria maxima (Hartm.) Holmb. growing along the banks of the river Odra near Szczecin (53o26'N, 14o35'E) in north-western Poland (Błaszkowski and Tadych 1997). Later, this fungus has also been found in maritime dunes of the Vistula Bar (54o24'N, 19o30'E; Błaszkowski et al. 2002) and some cultivated sites of the Western Pomerania (Iwaniuk and Błaszkowski, pers. observ.).
There is no information of the occurrence of this fungus in other regions of the world.
NOTES. Spores of Gl. verruculosum most resemble those of Gl. pansihalos S.M. Berch & Koske in colour, size, and in having an ornamentation formed by warts. However, the warts of the former project inward rather than outward as in the latter (Berch and Koske 1986). Additionally, the outermost spore wall layer of Gl. verruculosum is evanescent, whereas that of Gl. pansihalos is expanding. Finally, the innermost spore wall layer 3 of Gl. verruculosum usually tightly adheres to the laminate layer 2, and the third layer of the wall of Gl. pansihalos spores easily separates from it.
Other species of arbuscular fungi forming glomoid spores with warts are Gl. callosum Sieverd., Pacispora chimonobambusae (C.G. Wu & Y.S. Liu) Oehl & Sieverd., and Pac. scintillans (S.L. Rose & Trappe) Sieverd. & Oehl. In all these species, the warts occur on the surface of hyaline to white spores of a different wall structure than that of Gl. verruculosum (Błaszkowski 1988; Rose and Trappe 1980; Sieverding 1988; Walker, Schüßler 2004; Walker et al. 2004; Wu et al. 1995).
Intact spores of Gl. verruculosum in early stages of development of warts on the inner surface of the semirigid spore wall layer 3 may easily be confused with those of Gl. geosporum (Nicol. & Gerd.) C. Walker due to similarity in colour, size, and properties of their subtending hyphae (Błaszkowski, pers. observ.; Miller and Jeffries 1994; Morton 2000; Walker 1982). However, the third wall layer of both young and mature Gl. geosporum spores always is smooth, whereas spore wall layer 3 in Gl. verruculosum is warty. Additionally, the outermost spore wall layer of Gl. geosporum stains in Melzer's reagent, and that of Gl. verruculosum does not react in this reagent.
Spores of Gl. verruculosum also resemble smooth Gl. multiforum spores (Błaszkowski and Tadych 1997). However, most mature spores of the latter fungus are pitted (vs. spores with only smooth surface in Gl. verruculosum).
REFERENCES
Berch S. M., Koske R. E. 1986. Glomus pansihalos: a new species in the Endogonaceae, Zygomycetes. Mycologia 78, 838-842.
Błaszkowski J. 1988. Four new species of the Endogonaceae (Zygomycotina) from Poland. Karstenia 27, 37-42.
Błaszkowski J., Tadych M. 1997. Glomus multiforum and G. verruculosum, two new species from Poland. Mycologia 89, 804-811.
Błaszkowski J., Adamska I., Czerniawska B. 2002. Arbuscular mycorrhizal fungi (Glomeromycota) of the Vistula Bar. Acta Mycol. 37, 39-62.
Miller A. S., Jeffries P. 1994. Ultrastructural observations and a computer model of the helicoidal appearance of the spore wall of Glomus geosporum. Mycol. Res. 98, 307-321.
Morton J. B. 2000. International Culture Collection of Arbuscular and Vesicular-Arbuscular Mycorrhizal Fungi. West Virginia University.
Rose S. L., Trappe J. M. 1980. Three new endomycorrhizal Glomus spp. associated with actinorrhizal shrubs. Mycotaxon 10, 413-420.
Sieverding E. 1988. Two new species of vesicular arbuscular mycorrhizal fungi in the Endogonaceae from tropical high lands of Africa. Angew. Bot. 62, 373-380.
Walker C. 1982. Species in the Endogonaceae: a new species (Glomus occultum) and a new combination (Glomus geosporum). Mycotaxon 15, 49-61.
Walker C., Błaszkowski J., Schwazott D., Schüßler A. 2004. Gerdemannia gen. nov., a genus separated from Glomus, and Gerdemanniaceae fam. nov., a new family in the Diversisporales based on the former Glomus scintillans. Mycol. Res. 108(6), 707-718.
Walker C., Schüßler A. 2004. Nomenclatural clarifications and new taxa in the Glomeromycota. Mycol. Res. 108, 979-982.
Wu C.-G., Liu Y.-S., Hwuang Y.-L., Wang Y.-P., Chao C.-C. 1995. Glomales of Taiwan: V. Glomus chimnobambusae and Entrophospora kentinensis, spp. nov. Mycotaxon 53, 283-294.