Glomus laccatum Błaszk.

SPORES single in the soil; hyaline, glistening; globose to subglobose; (50-)87(-130) µm diam; sometimes ovoid; 120-130 x 80-85 µm; with one subtending hypha.

SUBCELLULAR STRUCTURE OF SPORES consists of one wall with two layers (swl1 and 2).

In PVLG+Melzer's reagent
In PVLG

Layer 1 evanescent, hyaline, 0.5-0.8 µm thick, tightly adherent to layer 2, usually absent in mature spores.

Layer 2 laminate, hyaline, smooth, (5.9-)7.2(-7.9) µm thick, composed of easily separating sublayers, each (0.5-)1.2(-2.2) µm thick.

Layers 1 and 2 do not stain in Melzer’s reagent.

SUBTENDING HYPHA hyaline; straight or curved; slightly funnel-shaped; (7.4-)9.7(-12.9) µm wide at the spore base.

In PVLG
Wall of subtending hypha hyaline; (3.0-)3.6(-3.9) µm thick at the spore base; composed of two layers (shwl1 and 2) continuous with spore wall layers 1 and 2; layer 1 rarely present in mature spores.

Pore gradually narrows with age because of thickening of the inner layer of subtending hypha.

 

GERMINATION. Not observed.

MYCORRHIZAE. In the field, Gl. laccatum has been associated with vesicular-arbuscular mycorrhizal roots of Ammophila arenaria (L.) Link, Helictotrichon pubescens (Huds.) Pilg., and an undetermined Festuca sp. (Błaszkowski 1988; Błaszkowski et al. 2002; Tadych and Błaszkowski 2000b; Iwaniuk and Błaszkowski, unpubl.). Many attempts to establish Gl. laccatum mycorrhizae in one-species cultures with Plantago lanceolata L. as the plant host failed.

DISTRIBUTION. Glomus laccatum has infrequently been recorded in Poland. Błaszkowski (1988) described this fungus from spores revealed in the rhizosphere soil of Festuca sp. growing in Jastrzebia Góra (55o18’N, 17o54’E). Later, Błaszkowski (1994) and Tadych and Błaszkowski (2000a) found its presence among roots of A. arenaria and H. pubescens growing in the Hel Peninsula (54o36'-54o47'N, 18o25'-18o48'E) and the Slowinski National Park (54o45'N, 17o26'E). However, other investigations with trapping arbuscular fungi in pot cultures indicated that Gl. laccatum is a relatively frequent inhabitant of both cultivated and uncultivated sites of Poland (Błaszkowski et al. 2002; Tadych and Błaszkowski 2000b; Iwaniuk and Błaszkowski, unpubl.).

Walker (pers. comm.) found this fungus in soils of the Great Britain. The infrequent disclosures of Gl. laccatum in field-collected soil samples may result from the lack or irregular sporulation of this fungus in the field conditions or a low persistency of its spores. In the field, a great part of arbuscular fungi either do not sporulate at all or their sporulation is infrequent and seasonal (Stürmer and Bellei 1994; Stutz and Morton 1996). Glomus laccatum forms small, hyaline spores with a delicate spore wall that may easily be decomposed by soil microorganisms. Many soil microorganisms are parasites of AMF (Lee and Koske 1994).

NOTES. Apart from Gl. laccatum, other species of arbuscular fungi forming glomoid hyaline spores are Gl. diaphanum J.B. Morton & C. Walker, Gl. viscosum Nicol., and Paraglomus occultum (C. Walker) J.B. Morton & D. Redecker.

The spore wall of Gl. diaphanum consists of three layers with a flexible innermost layer (Morton and Walker 1984; Morton 2000), whose lacks Gl. laccatum. Spores of Gl. viscosum occur in loose aggregates (Walker et al. 1995), and not singly in the soil as those of Gl. laccatum. Additionally, the spore wall of Gl. viscosum consists of three layers (Morton 2000), whereas that of Gl. laccatum contains two layers. Paraglomus occultum produces spores with three uniform layers (vs. two, phenotypically different layers in Gl. laccatum).

REFERENCES

Błaszkowski J. 1988. Three new vesicular-arbuscular mycorrhizal fungi (Endogonaceae) from Poland. Bull. Pol. Ac. Sci. Biol. Sci. 36, 10-12.

Błaszkowski J. 1994. Arbuscular fungi and mycorrhizae (Glomales) of the Hel Peninsula, Poland. Mycorrhiza 5, 71-88.

Błaszkowski J., Adamska I., Czerniawska B. 2002. Arbuscular mycorrhizal fungi (Glomeromycota) of the Vistula Bar. Acta Mycol. 37, 39-62.

Morton J. B. 2000. International Culture Collection of Arbuscular and Vesicular-Arbuscular Mycorrhizal Fungi. West Virginia University.

Lee P. J., Koske R. E. 1994. Gigaspora gigantea: parasitism of spores by fungi and actinomycetes. Mycol. Res. 98, 458-466.

Morton J. B., Walker C. 1984. Glomus diaphanum: a new species in the Endogonaceae common to West Virginia. Mycotaxon 21, 431-440.

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.

Stürmer S. L., Bellei M. M. 1994. Composition and seasonal variation of spore populations of arbuscular mycorrhizal fungi in dune soils on the island of Santa Catarina, Brazil. Can. J. Bot. 72, 359-363.

Tadych M., Błaszkowski J. 2000a. Arbuscular fungi and mycorrhizae (Glomales) of the Slowinski National Park, Poland. Mycotaxon 74, 463-483.

Tadych M., Błaszkowski J. 2000b. Arbuscular mycorrhizal fungi of the Brda river valley in the Tuchola Forests. Acta Mycol. 35, 3-23.

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.