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A new species of Poroconiochaeta from Russian soils

     Instituto de Investigaciones Fundamentales en Agricultura Tropical, Alejandro de Humboldt, calle 1 esq. 2, Santiago de las Vegas, Boyeros, C. de La Habana, Cuba

A. M. Stchigel
J. Guarro ¹

     Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, C/ Sant Llorenç 21, 43201, Reus, Tarragona, Spain

	ABSTRACT

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Poroconiochaeta tetraspora sp. nov., isolated from soil of Russia, is described and illustrated. The new taxon differs from P. discoidea in its four-spored asci (eight-spored in P. discoidea) and from P. punctulata in the pattern of ascospore ornamentation, which is conspicuously pitted in P. tetraspora (punctulate in the other species). The new combination Poroconiochaeta savoryi is proposed and discussed.

Key words: Ascomycota, Coniochaetaceae, soil-borne fungi

	INTRODUCTION

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The genus Poroconiochaeta Udagawa & Furuya was introduced to include two new species, P. discoidea Udagawa & Furuya and P. punctulata Udagawa & Furuya, characterized by ostiolate ascomata and one-celled, dark, ornamented ascospores, with an equatorial to lateral germ slit (Udagawa and Furuya 1979).

During a study of ascomycetes from Russia, an interesting fungus was isolated. It is characterized by its globose to pyriform, nonostiolate or ostiolate ascomata, and ellipsoidal, conspicuously pitted ascospore with a longitudinal germ slit. Based on these features, this fungus was identified as Poroconiochaeta. However, it shows a combination of characters not seen in the previously described species and is described here as a new species.

	MATERIALS AND METHODS

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Soil samples were collected in Chujonskoye, near Bubenize, Toropetskiy district, Tverskaya region, Russia. The area is characterized by a continental climate, with a temperature range of -31 to +25 C and annual precipitation of 550–750 mm. The region belongs to the taiga, with cultivated areas and boreal southerly woods, composed mainly of Alnus spp., Betula pendula Roth, B. pubescens Ehrh., Picea abies (L.) H. Karst., Pinus spp., Populus tremula L., Salix spp., and Sorbus aucuparia L.

The methods used for sampling have been described by Stchigel et al (1998). Approximately 1 g of soil was treated with 2% (p/v) phenol (Phenol crystal, Panreac, Barcelona, Spain) for 10 min. The supernatant was discarded and the solid phase was resuspended in 10 mL of sterilized water. The suspensions were cultured on potato-carrot agar (PCA, potatoes, 20 g; carrot, 20 g; tap water, 1000 mL) at 15 C in the dark. Isolates were grown on oatmeal agar (OA; Difco, Detroit, USA), PCA, and malt-extract agar (MEA, Difco, Detroit, USA) at room temperature (22–25 C), or incubated at 15, 25 and 35 C. Measurement of the fungal structures and photomicrographs were made as described by Stchigel et al (1998). Color notations in parentheses are from Kornerup and Wansher (1984).

	TAXONOMY

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Poroconiochaeta tetraspora D. García, Stchigel et Guarro, sp. nov. Figs. 1–8

View larger version (44K): [in this window] [in a new window]   FIGS. 1, 2. Poroconiochaeta tetraspora FMR-7401. 1. Ascus with ascospores. 2. Ascospores. Scale bars: 1, 2 = 10 µm

Mycelium composed of hyaline to pale yellowish-brown hyphae, becoming dark in the immediate vicinity of the ascomata, septate, branched, frequently anastomosing, smooth-walled, 1–6 µm diam. Colonies on PCA growing rapidly, attaining 71–86 mm diam in 14 d at room temperature, flat, thin, consisting of submerged mycelium and sparse aerial hyphae, dark olive-brown (M. 4F4) due to production of abundant, radially disposed ascomata; reverse olive-brown (M. 4F4). Ascomata, 146–200 x 80–120 µm, superficial to immersed, scattered or aggregated in small clusters, ostiolate or nonostiolate, pyriform to subglobose, or globose, translucent, appearing dark brown to black due to mass of ascospores glabrous. Peridium 3–5-layered, translucent, membranaceous, yellowish-brown to brown, with textura angularis, composed of thin-walled polygonal cells 6–14 µm diam. Asci four-spored (sometimes two- or three-spored), fasciculate, cylindrical, 55–70(–77) x 10–14 µm, rounded at the tip, without apical structures, short-stipitate, thin-walled, evanescent. Paraphyses 1–2 µm diam, numerous, hyaline, filiform, septate, simple or branched, swollen at the base. Ascospores (18–)20–24 x 9–13 µm, uniseriate, broadly fusiform, hyaline when young, becoming dark olivaceous-brown when mature, conspicuously ornamented by numerous circular to elongate pits, measuring 4–5 x 0.5 µm; germ slit lateral to equatorial, extending the entire length of the ascospores. Anamorph unknown.

On OA at room temperature, colonies attaining 55–62 mm diam in 14 d, dark olive-brown (M. 4F4), with radial production of the ascomata. On MEA at room temperature, colonies attaining 63–70 mm diam in 14 d, pastel-red (M. 7A4), slightly zonate, radially wrinkled, and slightly cottony; ascomata not produced. At 15 C colonies attaining 50–65 mm diam in 14 d, ascomata were poorly produced on both culture media. At 35 C growing slowly, attaining 15–25 mm diam in 14 d, ascomata not produced.

Specimens examined: RUSSIA. CHUJONSKOYE: Toropetskiy district. From soil, 22-III-2000, col. Natalia Sastre, isol. D. García. (HOLOTYPE: IMI 386072; ISOTYPE: FMR 7401); Poroconiochaeta tetraspora (FMR 7415).

Other specimen examined: Poroconiochaeta punctulata, ARGENTINA. TUCUMAN PROVINCE: Cerro San Javier. From soil, 15-V-2000, col. A.M. Stchigel, J. Guarro and J. Cano, isol. D. García (FMR 7408).

The genus Poroconiochaeta is closely related to Coniochaeta (Sacc.) Cooke. Both genera are distinguished by the ornamentation of the ascospores, which are pitted or punctulate in the former and smooth in the latter (Arx 1981). Those morphologically related species with nonostiolate ascomata and smooth ascospores are included in Coniochaetidium Malloch & Cain (Malloch and Cain 1971). Poroconiochaeta tetraspora had ostiolate and nonostiolate ascomata in the same culture, which at first created some confusion concerning to the adequate placement of this taxon. However, we agree with Arx (1973), who considered the presence of an ostiole a variable character, not always useful for the delimitation of genera. Thus, in spite of the presence of cleistothecial ascomata, we included the fungus in Poroconiochaeta, on the basis of its pitted ascospores. Poroconiochaeta tetraspora easily can be differentiated from the other species of the genus by its four-spored asci. The ornamentation of the ascospores resembles that of Poroconiochaeta discoidea, but this species has eight-spored asci, and discoid and smaller ascospores ((8–)9–12 x 8–11 µm). Poroconiochaeta punctulata also has similar ascospores, but they are finely pitted.

Thielavia savoryi Booth (Booth 1961) is characterized by nonostiolate ascomata, four-spored asci and fusoid ascospores, which are slightly flattened on one side. The species was included in Coniochaetidium Malloch & Cain (Malloch and Cain 1971) based on the presence of a germ slit in the ascospores (Malloch and Cain 1971). Later, due to the fasciculate arrangement of asci with a parallel disposition and plane convex ascospores, it was considered the type species of the new genus Germslitospora Lodha (Lodha 1978). Udagawa and Furuya (1979), based primarily on ascospore ornamentation, considered the new genus to be justified. This genus, however, has not been generally accepted (Arx 1981, Hawksworth et al 1995, Guarro et al 1997). Considering the ornamentation of the ascospores, we think this species should be included in Poroconiochaeta. Therefore, this new combination is proposed:

Poroconiochaeta savoryi (Booth) D. García, Stchigel & Guarro, comb. nov.

Thielavia savoryi Booth, Commonw. Mycol. Inst. Mycol. Pap. 83:3.1961. (Basionym).

Coniochaetidium savoryi (Booth) Malloch & Cain, Can. J. Bot. 49. 880. 1971. Germslitospora Lodha, in: Taxonomy of Fungi (CV Subramanian. ed) 250. 1978.

type: Germslitospora savoryi (Booth) Lodha (IMI 076253b)

Key to Poroconiochaeta species.

1. Asci 8-spored . . . . . 2

1'. Asci 4-spored . . . . . 3

     2. Ascospores discoid; phialidic anamorph present . . . . . P. discoidea.

     2'. Ascospores ellipsoidal; anamorph absent. . . . . . P. punctulata.

3. Ascospores smooth under light microscopy, finely pitted under scanning electron microscopy. . . . . . P. savoryi.

3'. Ascospores conspicuously ornamented with circular to elongate pits, up to 5 µm long . . . . . P. tetraspora.

View larger version (99K): [in this window] [in a new window]   FIGS. 3–8. Poroconiochaeta tetraspora FMR-7401. 3. Perithecial ascoma. 4. Cleistothecial ascoma. 5. Ascus. 6, 7. Ascospores. 8. Ascospores (SEM). Scale bars: 3, 4 = 20 µm, 5–8 = 10 µm

	ACKNOWLEDGMENTS

	FOOTNOTES

 
¹ Corresponding author. E-mail: umb{at}fmcs.urv.es

Accepted for publication November 25, 2002.

	LITERATURE CITED

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS TAXONOMY LITERATURE CITED

 
Arx JA von., 1973 Ostiolate and nonostiolate Pyrenomycetes. Proc K Ned Akad Wet Amsterd C 76:289-296

———. 1981 The genera of fungi sporulating in pure culture. 3rd ed. Vaduz: J Cramer 424 p

Booth C., 1961 Studies of Pyrenomycetes: Vl. Thielavia, with notes on some allied genera. Mycol Pap 83:1-15

Guarro J, Gené J, Al-Bader SM, Abdullah SK., 1997 A new species of Coniochaetidium from soil. Mycoscience 38:123-125

Hawksworth DL, Kirk PM, Sutton BC, Pegler DN., 1995 Ainsworth & Bisby's dictionary of the fungi. 8th ed. Wallingford, UK: International Mycological Institute, CAB International. 616 p

Kornerup A, Wanscher JH., 1984 Methuen handbook of colour. 3rd ed. London; Eyre Methuen. 252 p

Lodha BC., 1978 Generic concepts in some Ascomycetes occurring on dung. In: Subramanian CV, ed. Taxonomy of fungi (Proc. Inter. Symp. Taxonomy of Fungi. Univ. Madras. 1970). Madras: Univ. Madras. Part 1, p 241–257

Malloch D, Cain RF., 1971 New cleistothecial Sordariaceae and a new family, Coniochaetaceae. Can J Bot 49:869-880

Stchigel AM, Cano J, Guarro J., 1998 A new Gelasinospora from Argentinian soil. Mycol Res 102:1405-1408

Udagawa S-I, Furuya K., 1979 Poroconiochaeta, a new genus of the Coniochaetaceae. Trans Mycol Soc Japan 20:5-12

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