Mycologia, 96(2), 2004, pp. 418-423.
© 2004 by The Mycological Society of America
Systematics
Amauromyces farinaceous, rare known species and new record from Taiwan
Chee-Jen Chen 1
Department of Biotechnology, Southern Taiwan University of Technology, Yung-Kang, 71043 Taiwan
Franz Oberwinkler
Institute of Botany and Mycology, University of Tübingen, 72076 Tübingen, Germany
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ABSTRACT
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Amauromyces farinaceous is investigated. The species is a rare corticiaceous Homobasidiomycete recently collected in Taiwan. The unique basidial morphology, cell walls and septal pores of the hyphae are studied by transmission electron microscopy. The study demonstrates the gradual thickening of cell walls in the lower parts of young basidia, leaving only a small asymmetric cytoplasmic channel in mature stages. Systematics of genus Amauromyces are discussed by comparing it with Athelia, Athelopsis, Chaetoderma, Columnocystis, Gloeosoma, Paullicorticium, Sistotremastrum, Trechispora, Tulasnella and Veluticeps.
Key words: Amauromyces, Corticiaceae, dolipores, perforate parenthesomes, thick-walled basidia, ultra-structure
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INTRODUCTION
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Basidial morphology and ontogeny form important characteristics in the systematic phylogeny of corticiaceous Homobasidiomycetes (Eriksson 1958
; Oberwinkler 1965 Oberwinkler 1982). For example, characteristics of the hyphae, basidial shapes, number of sterigmata, pattern of the basidial succession and cystidial characters are used to define genera. Whereas long cylindrical basidia are produced in most genera of corticiaceous Homobasidiomycetes, species of only a few genera have short, cylindrical to stout clavate basidia, such as Amauromyces Jülich, Athelia Pers. emend Donk, Athelopsis Oberw. ex Parm., Paullicorticium John Erikss., Sistotremastrum John Erikss. and Trechispora Karst. (Eriksson 1958, Oberwinkler 1965, Jülich 1978). Basidial wall swelling in Homobasidiomycetes were reported only in a single species, which led to the erection of the genus Amauromyces with the new species A. pallidus Jülich ( Jülich 1978). Similar material was not found again until the publication of a second species, A. farinaceus Boidin, Lanquetin & Gilles (1993).
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MATERIALS AND METHODS
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In developing the descriptions and illustrations for this examination, different developmental stages of material were studied with a Zeiss Lab16 standard light microscope, using phase optics. In preparation for transmission electron microscopy, samples were fixed in 2% glutaraldehyde in 0.1 M sodium cacodylate buffer at pH 7.2 overnight or during several days. After six transfers in 0.1 M sodium cacodylate buffer, the material was postfixed in 1% OsO4 in the same buffer for 2 h in the dark, washed in distilled water and stained in 1% uranyl acetate solution for 1 h in the dark. After five washes in distilled water, the material was dehydrated in acetone for 10 min in 25, 50, 70, 95 and 100% concentrations, respectively. The material then was embedded in Spurr’s plastic (Spurr 1969). Series of sections were cut on a Reichert ultramicrotome using a diamond knife. After mounting the sections on Formvar-coated single-slot copper grids, they were stained with lead citrate at room temperature for 3–5 min and washed again with water. The sections were examined with a Zeiss EM 109 transmission electron microscope at 80 kV.
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TAXONOMY
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Amauromyces farinaceus FIGS. 1–7
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FIG. 1. Amauromyces farinaceus. Sections through basidiocarp with subhymenial hyphae, basidia in various stages of development, and basidiospores. Note thickening of hyphal walls and lower parts of basidia. Bars: 2.5 µm for spores and 5 µm for basidiospores.
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FIGS. 4–7. Transmission electron micrographs of Amauromyces farinaceus. 4, 5. Longitudinal sections of basidia. Note fibrous structure of swollen cell walls. 6, 7. Median sections of dolipores. Note dolipore swellings, electrondense bandings in the orifice, perforated parenthesomes and spongy structure of cell walls. Bars: 4, 5 = 0.5 µm; 6, 7 = 0.2 µm.
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Basidiocarps of A. farinaceus are corticioid, whitish to hyaline, 40–80 µm thick and grow on decayed wood. The hyphal system is monomitic and consists of hyaline, fibulate, 2–4 µm thick hyphae that are thickened irregularly. The walls consist of a spongy to fibrous matrix. Hyphae adnate to the substrate are long-celled and loosely interwoven. Those of the subhymenium are short-celled and densely packed. According to observations with the light microscope, the cytoplasm of hyphal cells apparently contains oily components. As seen by transmission electron microscopy, hyphae have septa with dolipores with perforate parenthesomes (FIGS. 6, 7) and spongy cell-wall thickening (FIGS. 4, 5). There are no cystidia, gloeocystidia or hyphidia. Basidia produce four sterigmata, are predominantly short-ellipsoidal, 7–15 (–20) x 4–5 µm, and arranged mostly in basidial clusters developing by lateral outgrowths of clamps. One conspicuous feature is cell-wall swelling in the lower parts of the basidia. As seen by transmission electron microscopy, wall-thickening develops in young basidial stages and continues to enlarge asymmetrically inward, finally leaving a cytoplasmic channel that is narrow at the base of the basidia, broader in the middle and open to full size in the upper parts of the basidia (FIGS. 4–7). The four sterigmata are characteristically homobasidiomycetous, small, 3–4 µm long, giving rise to asymmetrically attached spores. Basidiospores are ellipsoidal to slightly curved, 4 x 1.5–2 µm, thin- and smooth-walled and nonamyloid. Germination was not observed. Specimen was collected at Yangmingshan National Park in Taipei, Taiwan, 300 m, 29.4.1996, leg. Chee-Jen Chen CCJ1446, in herbario TNM in Taiwan.
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DISCUSSION
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The ultrastructure of septal pores and walls of hyphae and basidia are reported here for the first time in a species of Amauromyces. Scattered spongy swellings of walls of basidiomycetous hyphae (FIGS. 4, 5) hitherto were reported only for species of Tulasnella J. Schroet (R. Bauer in Kirschner and Oberwinkler 2001, Langer 1994). The unique feature of A. farinaceus is the conspicuous, asymmetrical apposition of additional cell-wall material in the lower parts of the basidia, showing a fibrous structure in longitudinal sections (see FIGS. 4, 5). The species is identified as A. farinaceus in the conspicuous structures and in the size of basidia, basidiospores and hyphae. Amauromyces pallidus has larger basidia in basal parts that often are thick-walled ( Jülich 1978), while A. farinaceus has smaller basidia and larger basidiospores (Boidin et al 1993). Basal parts of basidia with small cytoplasm channels remaining within the cell-wall swellings never had been reported in other species. Dolipores with perforate parenthesomes (FIGS. 6, 7) indicate that A. farinaceus is a taxon of the Homo-basidiomycetes (Oberwinkler 1985).
Among the few corticiaceous genera containing species with short cylindrical to stout clavate basidia, only Paullicorticium and Sistotremastrum appear to be more closely related to Amauromyces. When all morphological characters, including basidial structure and ontogeny, cystidia, hymenial hyphal structure, etc. are compared, species of these genera share thin corticiaceous basidiocarps, monomitic hyphal systems and short basidia. In addition, these genera are devoid of any kind of cystidial cells.
Apart from the absence of cell-wall thickening in the basidia of Paullicorticium and Sistotremastrum species, these species differ from those of Amauromyces by producing more than four sterigmata per basidium (Eriksson 1958, Oberwinkler 1965, Eriksson et al 1981). Furthermore, dolipores in Paullicorticium pearsonii (Bourd.) John Erikss have continuous parenthesomes (Oberwinkler 1985).
Swelling of the basidial walls in other members of corticiaceous Homobasidiomycetes was detected, namely in Chaetoderma Pharm., Columnocystis Pouz., Gloeosoma (Lév.) Bres., and Veluticeps (Cooke) Pat.. The morphology of basidia and structure of basidiocarps of these genera differ from those of Amauromyces farinaceus. When other taxonomically important characters such as basidiocarp features, hyphal systems, hymenial configurations and basidial shapes and spore characters are considered, it is obvious that these genera are not related to Amauromyces. Gloeosoma is related to Aleurodiscus Rabenh. ex Schroet. (Nuñez and Ryvarden 1997); Chaetoderma, Columnocystis (= Veluticeps) to stereoid taxa (unpublished).
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FIG. 2. Amauromyces farinaceus. Basidial clusters with basidia in various stages of development are shown. Note thickening of hyphal walls and lower parts of basidia. Bar = 5 µm.
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FIG. 3. Amauromyces farinaceus. Basidial ontogeny is illustrated. Note successive thickening of cell walls of lower parts of basidia. Bar = 5 µm.
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ACKNOWLEDGMENTS
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We are indebted to Prof. Nils Hallenberg and Dr. Roland Kirschner for critically reading the manuscript. This study was supported partly by the National Science Council of Taiwan (NSC 86-2311-B002-005 and NSC 91-2311-B218-001). Financial support for joint mycological research in Taiwan from the National Science Council of Taiwan and the German Academic Exchange Service (Deutscher Akademischer Austauschdienst, DAAD) is gratefully acknowledged.
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FOOTNOTES
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1 Corresponding author. E-mail: c5200999{at}mail.stut.edu.tw
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LITERATURE CITED
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Boidin J, Lanquetinp, and Gilles G. 1993. Basidiomycetes Aphyllophorales de l’ile de la Breunion. XVII: Les genres Amauromyces, Cunninghammyces et Repetobasidium. Bull. Soc. Mycol. France.
109(2):93–100.
Eriksson J. (1958). Studies in the Heterobasidiomycetes and Homobasidiomycetes—Aphyllophorales of Muddus National Park. Symb Bot Ups
16:1–172.
Eriksson J, Hjortstam K, Ryvarden L. 1981. The Corticiaceae of North Europe 6. Oslo: Fungiflora. p 1051–1276.
Jülich W. 1978. On some Aphyllophorales from Australia. Personnia
9:456.
Kirschner R. and Oberwinkler F. 2001. Mycoparasitism by three species of Diplococcium (Hyphomycetes). Plant Biology
3:449–454.
Langer G. 1994. Die Gattung Botryobasidium Donk (Corticiaceae, Basidiomycetes). Bibliotheca Mycologica 158. Stuttgart: J. Cramer.
Nuñez M, Ryvarden L. 1997. The genus Aleurodiscus (Basidiomycotina). Synopsis Fungorum
12:1–164.
Oberwinkler, F. 1965. Primitive Basidiomyceten. Revision einiger Formenkreise von Basidienpilzen mit plastischer Basidie. Sydowia Ann Myc Ser II
. 19:1–72.
Oberwinkler. 1982. The significance of the morphology of the basidium in the phylogeny of Basidiomycetes. In: Wells K, Wells EK, eds. Basidium and basidiocarp. Evolution, cytology, function, and development. New York: Springer Verlag. p 9–35.
Oberwinkler. 1985. Anmerkungen zur Evolution und Systematik der Basidiomyceten. Bot Jahrb Syst
107:541–580.
Spurr, AR. 1969. A low viscosity epoxid embedding medium for electron microscopy. J Ultrastr Res
26:31–43.[Medline]
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ABSTRACT
INTRODUCTION
