Glomus deserticola Trappe et al.
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SPORES borne in the soil singly or in loose aggregates lacking a peridium; pale yellow (3A3) to orange (6A6); globose to subglobose; (70-)89(-115) µm diam; sometimes ovoid to pear-shaped; 70-80 x 85-100 µm; with one subtending hypha.
SUBCELLULAR STRUCTURE OF SPORES consists of one wall comprising two layers (swl1 and 2).
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In PVLG+Melzer's reagent |
In PVLG |
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Layer 1 mucilagenous, hyaline, (0.5-)0.6(-1.0) µm thick, staining pinkish (10A2) to bluish (11B8) in Melzer’s reagent, usually completely sloughed in mature spores.
Layer 2 laminate, smooth, pale yellow (3A3) to orange (6A6), (1.2-)2.4(-3.9) µm thick, frequently thickened at the spore base to form a collar.
Most juvenile spores with layer 1 only. Layer 2 forms when the formation of layer 1 is completed.
SUBTENDING HYPHA pale yellow (3A3) to orange (6A6); straight or curved; flared, funnel-shaped, rarely constricted; (6.4-)9.9(-15.7) µm wide at the spore base.
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In PVLG |
In PVLG+Melzer's reagent |
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Wall of subtending hypha pale yellow (3A3) to orange (6A6); (2.2-)2.6(-2.9) µm thick at the spore base; composed of two layers (shwl1 and 2), continuous with spore wall layers 1 and 2; layer 2 frequently with side thickenings.
Pore (1.7-)4.7(-8.6) µm wide, open or closed by a curved septum, continuous with the innermost laminae of the laminate spore wall layer 2.
GERMINATION. A germ tube emerges from the lumen of the subtending hypha.
MYCORRHIZAE. The mycorrhizae formed in one-species cultures of this fungus with Plantago lanceolata L. as the plant host consisted of arbuscules, vesicles, as well as intra- and extraradical hyphae. Arbuscules were irregularly distributed and had fine branches. Vesicles measured 33.9-57.2 x 51.3-137.3 µm and were usually highly scattered along roots. Intraradical hyphae were 1.4-8.9 µm wide and grew parallel to the root axis. They frequently had thickenings or short outgrowths. These hyphae sometimes formed coils, 14.2-27.2 x 26.3-60.0 µm and Y-shaped branches. Extraradical hyphae were 1.4-4.1 µm wide. In 0.1% trypan blue, arbuscules stained violet white (18A2) to greyish violet (18C4), vesicles pastel violet (18A4) to deep violet (18E8), intraradical hyphae violet white (18A2) to dull violet (18D4), coils pale violet (18A3) to greyish violet (18D7), and extraradical hyphae pastel violet (18A4) to greyish violet (18C5).
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In roots
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DISTRIBUTION. The author of this website has so far found spores of Gl. deserticola in 199 field-collected soil samples. Of them, 197 came from cultivated and uncultivated soils of Poland, and two were collected in natural sites of the Czech Republic and Lithuania. All the soils have been sampled from under 45 species in 12 plant families.
The literature data showing the origin of arbuscular mycorrhizal fungi used in experiments and their geographical occurrence indicate that Gl. deserticola has been found only in the U.S.A. (Augé 1989; Bloss and Walker 1987; Paulitz and Menge 1986; Sylvia 1986; Sylvia and Will 1988; Trappe et al. 1984; Will and Sylvia 1990), Spain (Arines and Vilarino 1991), Poland (Blaszkowski 1990, 1993a, b, 1994; Tadych, Blaszkowski 2000), and India (Ragupathy and Mahadevan 1993). However, the diversity of climatic and soil conditions of these countries, as well as the data on the fungus presented here suggest it to have a worldwide distribution. Additionally, Gl. deserticola has probably many times been mistakenly identified as Gl. fasciculatum (Walker and Koske 1987; Trappe et al. 1984), one of the most frequently reported arbuscular mycorrhizal fungus from soil surveys and most often cited as used in studies of plant growth responses (Walker 1985).
NOTES. When observed under a dissecting microscope, the species of the genus Glomus most resembling Gl. deserticola are Gl. aggregatum N.C. Schenck & G.S. Sm. emend. Koske, Gl. fasciculatum (Thaxt.) Gerd. & Trappe emend. C. Walker & Koske, Gl. intraradices N.C. Schenck & G.S. Sm., and Gl. hoi S.M. Berch & Trappe (Berch and Trappe 1985; Koske 1985; Stürmer and Morton 1997; Walker and Koske 1987). Spores of all the fungi occur singly or in aggregates in the soil, are yellow-coloured, and have a similar shape and size range. Glomus pustulatum Koske et al. and Gl. trimurales Koske & Halvorson also produce spores similar in colour and size, but they are formed only singly in the soil (Koske et al. 1986; Koske and Halvorson 1989).
Glomus deserticola differs from the species listed above in number, as well as in phenotypical and staining properties of its spore wall layers. They are most evident when spores crushed in a mixture of PVLG and Melzer’s reagent are examined under a compound microscope.
While the spore wall of Gl. deserticola consists of two layers: a mucilaginous layer adherent to a laminate layer, that of spores of Gl. aggregatum, Gl. fasciculatum, and Gl. intraradices contains three layers. Glomus deserticola lacks the flexible innermost layer of Gl. fasciculatum (Walker and Koske 1987) and the semiflexible middle layer of Gl. aggregatum and Gl. intraradices (Blaszkowski, pers. observ.; Stürmer and Morton 1997). Additionally, the outermost wall layer of Gl. fasciculatum spores is permanent and the innermost spore wall layer of Gl. intraradices consists of readily separating sublayers (laminae). In contrast, the outer layer of Gl. deserticola spores sloughs with age, and their inner laminate layer consists of tightly adherent laminae. Finally, only the outermost mucilaginous layer of spores of Gl. deserticola, Gl. aggregatum and Gl. intraradices reacts in Melzer’s reagent, whereas all three layers of Gl. fasciculatum spores stain in this reagent. Additionally, the unique property of Gl. aggregatum is the production of inner spores by internal proliferation (Koske 1985; Blaszkowski 1991).
Although Gl. hoi is described to produce two-layered spores as does Gl. deserticola, the outer layer of the former fungus is thicker and coloured, and that of the latter species is thinner and colourless (Berch and Trappe 1985; Morton 2000).
The spores of Gl. pustulatum and Gl. trimurales have a wall composed of three permanent layers, of which none stains in Melzer’s reagent (Blaszkowski, pers. observ.; Koske and Halvorson 1989; Koske et al. 1986; Morton 2000; vs. two layers with an outer layer staining reddish white to bluish red in this reagent in Gl. deserticola).
REFERENCES
Arines J., Vilarino A. 1991. Growth, micronutrient content and vesicular-arbuscular fungi infection of herbaceous plants on lignite mine spoils: a greenhouse pot experiment. Plant and Soil 135, 269-273.
Augé R. M. 1989. Do VA mycorrhizae enhance transpiration by affecting host phosphorous content? J. Plant nutrition 12, 743-753.
Berch S. M., Trappe J. M. 1985. A new species of Endogonaceae, Glomus hoi. Mycologia 77, 654-657.
Bloss H. E., Walker C. 1987. Some endogonaceous mycorrhizal fungi of the Santa Catalina Mountains in Arizona. Mycologia 79, 649-654.
Blaszkowski J. 1990. Polish Endogonaceae IV. Gigaspora gigantea, Glomus deserticola, and Glomus globiferum. Acta Mycol. 26, 3-16.
Blaszkowski J. 1991. Polish Endogonaceae. IX. Glomus aggregatum with spores forming an evanescent outermost wall. Crypt. Bot. 2/3, 130-135.
Blaszkowski J. 1993a. 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. 1993b. The occurrence of arbuscular fungi and mycorrhizae (Glomales) in plant communities of maritime dunes and shores of Poland. Bull. Pol. Ac. Sci. Biol. Sci. 41, 377-392.
Blaszkowski J. 1994. Arbuscular fungi and mycorrhizae (Glomales) of the Hel Peninsula, Poland. Mycorrhiza 5, 71-88.
Koske R. E. 1985. Glomus aggregatum emended: A distinct taxon in the Glomus fasciculatum complex. Mycologia 77, 619-630.
Koske R. E., Halvorson W. L. 1989. Scutellospora arenicola and Glomus trimurales: two new species in the Endogonaceae. Mycologia 81, 927-933.
Koske R. E., Friese C., Walker C., Dalpé Y. 1986. Glomus pustulatum: A new species in the Endogonaceae. Mycotaxon 26, 143-149.
Morton J. B. 2000. International Culture Collection of Arbuscular and Vesicular-Arbuscular Mycorrhizal Fungi. West Virginia University.
Paulitz T. C., Menge J. A. 1986. The effects of a mycoparasite on the mycorrhizal fungus, Glomus desertiola. Phytopathol. 76, 351-354.
Ragupathy S., Mahadevan A. 1993. Distribution of vesicular-arbuscular mycorrhizae in the plants and rhizosphere soils of the tropical plains, Tamil Nadu, India. Mycorrhiza 3, 123-136.
Stürmer S. L., Morton J. B. 1997. Developmental patterns defining morphological characters in spores of four species in Glomus. Mycologia 89, 72-81.
Sylvia D. M. 1986. Spatial and temporal distribution of ve- sicular-arbuscular mycorrhizal fungi associated with Uniola paniculata in Florida foredunes. Mycologia 78, 728-734.
Sylvia D. M., Will M. E. 1988. Establishment of vesicular-arbuscular mycorrhizal fungi and other microorganisms on a beach replenishment site in Florida. Appl. Environm. Microbiol. 54, 348-352.
Tadych M., Blaszkowski J. 2000. Arbuscular fungi and mycorrhizae (Glomales) of the Slowinski National Park, Poland. Mycotaxon 74, 463-483.
Trappe J. W., Bloss E., Menge J. 1984. Glomus deserticola sp. nov. Mycotaxon 20, 123-127.
Walker C. 1985. Taxonomy of the Endogonaceae. In: 6th North American Conference on Mycorrhizae. Proc. Ed., R. Molina. Forest Research Laboratory, Corvalis, Oregon, 193-198.
Walker C., Koske R. E. 1987. Taxonomic concepts in the Endogonaceae: IV. Glomus fasciculatum redescribed. Mycotaxon 30, 253-262.
Will M. E., Sylvia D. M. 1990. Interaction of rhizosphere bacteria, fertilizer, and vesicular-arbuscular mycorrhizal fungi with sea oats. Appl. Environm. Microbiol. 56, 2073-2079.
