SPORES single in the soil; hyaline to orange white (6A2); globose to subglobose; (70-)107(-165) µm diam; rarely ovoid; 100-130 x 110-150 µm.; with one subtending hypha.
SUBCELLULAR STRUCTURE OF SPORES composed of a spore wall and one, inner germination wall.
Spore wall consists of two layers (swl1 and 2).
Layer 1 permanent, rigid, hyaline to orange white (6A2); (0.7-)1.2(-1.5) µm thick; ornamented mainly with warts, 1.7-5.7 x 0.7-1.9 µm, rarely with ridges, 0.5-0.8 µm high, tightly adherent to layer 2; occasionally separating from layer 2 in vigorously crushed spores.
Layer 2 laminate, smooth, hyaline, (2.0-)3.5(-4.5) µm thick.Germination wall composed of two layers (gwl1 and 2).
Layer 1 flexible, hyaline, (0.2-)0.7(-1.2) µm thick, easily separating from layer 2.
Layer 2 flexible, coriaceous, hyaline, (1.2-)1.8(-2.8) µm thick, staining dull red (9B4) to deep red (11B8) in Melzer’s reagent.
GERMINATION SHIELD. A unit, hyaline to orange white (5A2), circular, 45.0-52.5 µm diam, more frequently ellipsoidal, 30-80 x 75-100 µm shield, with a sinuous or incised margin when observed in a plane view, ca. 0.5-0.8 µm thick when seen in a cross view. In the ca. 20 examined specimens with visible germination shields, only one, hyaline to orange white (5A2), 3.8-12.5 µm diam, germ tube developed from each of these shields was observed. The shield was located on the surface of the inner germination wall. Examination spores of different maturity suggested that the shield deteriorates with age and sometimes completely disappears.
SUBTENDING HYPHA hyaline; straight or slightly curved; cylindrical, sometimes slightly constricted at the spore base; (6.4-)8.7(-12.5) µm wide at the spore base.
GERMINATION. A germ tube develops from a germination shield and penetrates the spore wall.
MYCORRHIZAE. In one-species cultures with Plantago lanceolata L. as the plant host, Gl. dominikii formed mycorrhizae composed of arbuscules, vesicles, as well as intra- and extraradical hyphae staining intensively in 0.1% trypan blue.
Arbuscules in roots of P. lanceolata
In roots of P. lanceolata
NOTES. The wall of the most juvenile Gl. dominikii spores consists of only one layer (layer 1). Then, layer 2 origins due to synthesis firs a very thin, <0.5 µm thick, flexible structure (sublayer) and subsequently gradual addition of next sublayers. When the spore wall is completely differentiated, the inner germination wall layers 1 and 2 start to form successively. The beginning of the differentiation of the germination wall layer 2 signals its staining reaction in Melzer's reagent. The formation of the germination shield on the surface of the inner germination wall ends the ontogenetic development of Gl. dominikii spores.
Despite the lack of any data of the formation of a germination shield, the diagnostic descriptions and illustrations of spores of Gl. chimonobambusae Wu & Liu and Gl. scintillans Rose & Trappe (Rose and Trappe 1980; Wu et al. 1995) suggest that the latter two fungi and Gl. dominikii are conspecific.
The distinctly ornamented spores of the three fungal species are easy to separate from those of the other species of the genus Glomus. However, when observed under a dissecting microscope, spores of Gl. dominikii with small warts or low ridges resemble smooth spores of Gl. eburneum Kennedy et al., Gl. diaphanum Morton & Walker, Gl. laccatum Blaszk., Gl. viscosum Nicolson, and Paraglomus occultum (Walker) Morton & Redecker (Blaszkowski 1988b; Kennedy et al. 1999; Morton and Redecker 2001; Morton and Walker 1984; Walker 1982; Walker et al. 1995). Examination of the subcellular structure of spores under a compound microscope readily separates Gl. dominikii from the other species listed. None of them possesses a 2-layered germination wall with the inner layer showing a dextrinoid reaction.
Glomus dominikii and probably Gl. chimonobambusae and Gl. scintillans are untypical members of the genus Glomus. None of the other species of this genus forms an inner germination wall, whose both phenotypic and biochemical properties are most similar to those of the innermost germination wall of members of the genus Scutellospora. Additionally, the formation of a germination shield by Gl. dominikii and the position of this shield on the inner germination wall further bring nearer this fungus to Scutellospora spp. However, in contrast to fungi of the genus Scutellospora, Gl. dominikii produces mycorrhizae with vesicles.
Molecular properties of spores of Gl. dominikii confirmed that this fungus should be transferred to a new genus in a new family (Walker, pers. inf.).
Blaszkowski J. 1988a. Four new species of the Endogonaceae (Zygomycotina) from Poland. Karstenia 27, 37-42.
Blaszkowski J. 1988b. Three new vesicular-arbuscular mycorrhizal fungi (Endogonaceae) from Poland. Bull. Pol. Ac. Sci. Biol. Sci. 36, 10-12.
Blaszkowski J. 1993. Comparative studies of the occurrence of arbuscular fungi and mycorrhizae (Glomales) in cultivated and uncultivated soils of Poland. Acta Mycol. 28, 93-140.
Blaszkowski J. 1994. Arbuscular fungi and mycorrhizae (Glomales) of the Hel Peninsula, Poland. Mycorrhiza 5, 71-88.
Blaszkowski J., Tadych M., Madej T., Adamska I., Iwaniuk A. 2001. Arbuscular mycorrhizal fungi (Glomales, Zygomycota) of Israeli soils. Mat. II Polsko-Izraelskiej Konf. Nauk. nt. „Gospodarowanie zasobami wodnymi i nawadnianie roslin uprawnych”. Przeglad naukowy Wydz. Inz. Ksztalt. Srod. 22, 8-27.
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.
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.
Morton J. B., Walker C. 1984. Glomus diaphanum: a new species in the Endogonaceae common to West Virginia. Mycotaxon 21, 431- 440.
Tadych M., Blaszkowski J. 2000. Arbuscular fungi and mycorrhizae (Glomales) of the Slowinski National Park, Poland. Mycotaxon 74, 463-483.
Walker C. 1982. Species in the Endogonaceae: a new species (Glomus occultum) and a new combination (Glomus geosporum). Mycotaxon 15, 49-61.
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.
Wu C.-G., Liu Y.-S., Hwuang Y.-L., Wang Y.-P., Chao C.-C. 1995. Glomales of Taiwan: V. Glomus chimonobambusae and Entrophospora kentinensis, spp. nov. Mycotaxon 53, 283-294.