Studies in Mycology No. 8

15 January 1975

 

 

On Thielavia and some similar genera of ascomycetes

 

 

J. A. von Arx

 

Centraalbureau voor Schimmelcultures, Baarn

 

Summary

 

The genus Thielavia is restricted to Pyrenomycetes characterized by non-ostiolate ascomata with a wall of textura epidermoidea and ascospores with a single distinct germ pore; 18 species are recognized. The genus Chaetomidium is maintained for 6 species having ascomata with a pseudo-parenchymatous wall, covered with characteristic hairs, and limoniform ascospores with a single germ pore. The new genus Melanocarpus is introduced for Myriococcum albomyces Cooney & Emerson, a thermophilic fungus with dark, usually smooth, pseudoparenchymatous ascomata, and ovoid-oblate ascospores with a single distinct germ pore. Four species characterized by ascospores with two germ pores, one at each end, and by the formation of a Chrysosporium conidial state are classified in the genus Corynascus. A fungus with light ascomata covered with dark hyphae and having ellipsoidal ascospores with two prominent germ pores is described as type of tbe new genus Corynascella. Two further new species are described in the genera Thielavia and Apodus. Species with one-celled ascospores with a germ slit are classified in the genera Coniochaetidium and Ephemeroascus. Identification keys and descriptions of the genera are given.

 

 

Introduction

 

Thielavia Zopf, Chaetomidium (Zopf) Sacc. and other related, recently described genera of Ascomycetes are characterized by non-ostiolate ascomata and by one-celled, darkly pigmented ascospores having one or two germ pores. These genera were separated from each other mainly by characters such as the presence or absence of ascomatal hairs or setae. The species with thin-walled, smooth ascomata have usually been placed in Thielavia, whereas those with thick-walled, dark ascomata covered with hairs were classified in Chaetomidium. The genus Boothiella was erected for a similar fungus with light ascomata and 4-spored asci (Lodhi and Mirza, 1962). The genus Apodus, introduced by Malloch and Cain (1971) for a single species, is characterized by the occasionally tw0-celled ascospores, the thickened ascus tip and the thick-walled ascomata.

Malloch and Cain (1973) regarded the presence or absence of setae or hairs on the ascomata as a criterion of insufficient taxonomic value and listed Chaetomidium as a synonym of Thielavia. They considered Thielavia [p. 2] sensu lato to be closely related to Chaetomium, which should differ only in the formation of ostiolate ascomata. Only a few species were excluded: those with ascospores possessing a germ slit were classified in the genus Coniochaetidium (Malloch and Cain, 1971). Mouchacca (1973) on the other hand pointed out that Thielavia (even without Chaetomidium) comprises a heterogeneous group of fungi. Von Arx (1973a) excluded Thielavia sepedonium and some similar species having ascospores with two germ pores, one at each end, and proposed for them the genus Corynascus.

The present study, which deals mainly with living strains maintained in the CBS collection under the above-mentioned genus names, revealed evidence that the classification should be modified. In Thielavia basicola, the type species of the genus, the ascospores have a single, conspicuous germ pore. In contrast to the record given by Booth (1961), no ascospores with two germ pores could be observed in the type specimen. The typical species of Thielavia are thought to be more akin to Sordariaceae than to Chaetomium. Maintainance of the genus Chaetomidium is justified for the non-ostiolate counterparts of Chaetomium. The genus Boothiella on the other hand proved to be indistinguishable from Thielavia. Two fungi could not be classified in any known genus, the genera Melanocarpus and Corynascella will be introduced for them.

 

Key to the genera (see also Malloch and Cain, 1973)

 

1a.

Ascospores with 1 or 2 germ pores

2

1b.

Ascospores with a longitudinal or equatorial germ slit or furrow

8

 

 

 

2a.

Ascospores with a single germ pore

3

2b.

Ascospores with 2 germ pores

6

 

 

 

3a.

Asci with a refractive structure inside the often attenuated and truncate tip; ascospores occasionally 2-celled, ellipsoidal; wall of the ascomata dark, thick, pseudoparenchymatous

Apodus

3b.

Asci without refractive structures, usually apically rounded; ascospores usually 1-celled

4

 

 

 

4a.

Ascomata with a thin wall composed of tightly interwoven hyphae (textura epidermoidea), ascospores fusiform, clavate, obovate or ellipsoidal, with a conspicuous germ pore; mesophilic or thermophilic

Thielavia

4b.

Ascomata with a thick wall composed of rounded or flattened cells (pseudoparenchymatous); ascospores limoniform or oblate.

5

 

 

 

5a.

Thermophilic; ascomata smooth or nearly so; ascospores irregularly oblate, with a de Bary bubble; arthroconidia present

Melanocarpus

5b.

Not thermophilic; ascomata covered with characteristic setae or hairs; ascospores limoniform, flattened laterally; arthroconidia absent

Chaetomidium

 

 

 

6a.

Ascospores ellipsoidal or reniform, with a de Bary bubble and 2 prominent germ pores; ascomata with a light wall, covered with dark [p. 3] hyphae

Corynascella

6b.

Ascospores fusiform, without de Bary bubbles; wall of the ascomata light or dark, glabrous or occasionally setose

7

 

 

 

7a.

Ascomata with a dark wall composed of flattened, irregular, thickwalled cells; Chrysosporium conidial state present

Corynascus

7b.

Ascomata with a light, translucent wall; Chrysosporium conidial state absent (small phialoconidia often present)

Melanospora (Microthecium)

 

 

(not treated in this paper)

 

 

 

8a.

Ascospores longer than 5 m, with a distinct or prominent germ slit; conidial state not Verticillium-like; orange pigments usually formed

Coniochaetidium

8b.

Ascospores 3-5 m long, with an inconspicuous germ slit; conidial state Verticillium-like, phialidic; orange pigment absent

Ephemeroascus

 

 

Thielavia Zopf

 

Thielavia Zopf - Verh. bot. Ver. Prov. Brandenburg 18: 101. 1876.

Boothiella Lodhi & Mirza - Mycologia 54: 217. 1962.

Thielaviella v. Arx & Tariq Mahmood - Trans. Br. mycol. Soc. 51: 611. 1968.

 

Colonies spreading, white or light, rarely dark, often lanose or tufted, composed of septate, branched, usually hyaline hyphae; ascomata borne on hyphae, often covered by the aerial mycelium, spherical, non-ostiolate, glabrous, setose or tomentose, with a hyaline or brown wall composed of flattened hyphal cells (textura epidermoidea); asci parallel, in a fascicle or irregular, ellipsoidal, saccate or cylindrical, rarely clavate, with a rather persistent, thin wall, 4-8 spored; ascospores fusiform, ellipsoidal, obovate or clavate, 1-celled, brown, with a conspicuous germ pore; conidial states mostly absent, chlamydospore-like structures often present.

Type species: Thielavia basicola Zopf.

 

The genus Thielavia comprises non-ostiolate relatives of Sordariaceae. Other Sordariaceae with non-ostiolate ascomata have been classified e.g. in Echinopodospora, Zopfiella (syn.: Tripterospora) and Anixiella (= Gelasinospora).

 

 

Key to the species

 

1a.

Germ pore of the ascospores apical

2

1b.

Germ pore of the ascospores subapical

14

 

 

 

2a.

Wall of the ascomata hyaline or bright (old occasionally light brown)

3

2b.

Wall of the ascomata brown

7

 

 

 

3a.

Ascospores ovate-fusiform, 5-7 m wide; asci ellipsoidal

T. basicola [p. 4]

3b.

Ascospores 9-16 m wide

4

 

 

 

4a.

Ascospores fusiform, 22-26 m long

T. hyalocarpa

4b.

Ascospores ellipsoidal or nearly spherical, 10-20 m long

5

 

 

 

5a.

Ascospores nearly spherical, 10-13 m long; asci 8-spored, cylindrical

T. octospora

5b.

Ascospores broadly ellipsoidal, 14-20 m long

6

 

 

 

6a.

Asci cylindrical, 4-spored; ascospores 14-20 x 12-15 m

T. tetraspora

6b.

Asci obpyriform or broadly clavate, 8-spored; ascospores 16-20 x 15-19 m

T.pseudomaritima

 

 

 

7a.

Ascospores fusiform or ellipsoidal, 13-18 m long

8

7b.

Ascospores ovate, clavate, ellipsoidal or irregular, usually shorter than 14 m

9

 

 

 

8a.

Ascospores 7-9 m wide; ascomata smooth or tomentose

T. terricola

8b.

Ascospores 5-6 m wide; ascomata setose

T. peruviana

 

 

 

9a.

Ascospores 9-14 x 6-8 m, obovate, clavate or irregular

10

9b.

Ascospores usually smaller

11

 

 

 

10a.

Ascospores obovate or nearly clavate; ascomata usually setose

T. fragilis

10b.

Ascospores variable in shape, mostly irregular; ascomata smooth

T. variospora

 

 

 

11a.

Not thermophilic; ascomata covered with short setae; ascospores 6-8 x 5-6 m

T. minuta

11b.

Thermophilic; ascomata smooth or tomentose, often embedded in the mycelial mat; conidia often present

12

 

 

 

12a.

Ascospores 8-10 x 5-7 m, ellipsoidal

T. microspora

12b.

Ascospores 5-8 x 5-6 m, obovate or pyriform

13

 

 

 

13a.

Wall of the ascomata dark brown; ascospores usually ovate; clavate conidia with a truncate base, 3-6 x 2-3 m, present

T. terrestris

13b.

Wall of the ascomata light brown; ascospores often triangular in planar view; conidia absent or different

T. australiensis

 

 

 

14a.

Ascospores 6-11 x 5-7 m; ascomata smooth

T. coactalis

14b.

Ascospores longer

15

 

 

 

15a.

Ascomata setose or hairy; conidia (chlamydospores) absent; usually mesophilic

16

15b.

Ascomata smooth or covered with hyphae; conidia (chlamydospores) present; usually thermophilic

17

 

 

 

16a.

Ascomata covered with short, septate setae

T. appendiculata

16b.

Ascomata covered with long, hypha-like appendages

T. hyrcaniae

 

 

 

17a.

Ascospores 8-12 x 5-6.5 m

T. arenaria

17b.

Ascospores 14-19 x 8-10 m

T. subthermophila

[p. 5]

 

 

1. Thielavia basicola Zopf - Fig- 1

 

Thielavia basicola Zopf - Verh. bot. Ver. Prov. Brandenburg 18: 101. 1876.

Thielavia renominata Paclt - Parasitica 7: 110. 1951.

Thielavia terricola f. minor Rayss & Borut - Mycopath. Mycol. appl. 10: 160. 1959

= Thielavia minor (Rayss & Borut) Malloch & Cain - Mycologia 65: 1065 1973.

 

The following description is based on a study of the type specimen (Sydow, Mycotheca Marchia 80, in herb. B).

Developing on roots of Senecio elegans in association with Thielaviopsis basicola (Berk. & Br.) Ferraris (=Milowia nivea Massee). Ascomata spherical, non-ostiolate, smooth, usually surrounded by a felt of hyaline, septate, 1.5-3.5 m wide hyphae, 80-170 m in diameter, with a translucent, 8-11 m thick wall composed of light, usually straw coloured, 3-5 m wide, up to 15 m long, flattened cells (textura epidermoidea); asci ellipsoidal, 24-30 x13-17 m, evanescent; ascospores, ovate-fusiform, attenuated at both ends, often inequilateral, at one end rounded, at the other slightly truncate, 1-celled, brown, 10-12 x 5.5-6.5 m, with a thick wall darkened around the germ pore.

 

 

Fig. 1 Thielavia basicola, type collection (B). a. parts of the ascoma wall: b. asci: c. ascospores.

 

A gelatinous layer surrounding the ascospores or ascospores with 2 germ pores, as described by Booth (1961), could be observed neither in the type specimen, nor in freshly collected specimens on roots of Nicotiana tabacum.

 

Cultures of this fungus were not available- The strains sent to CBS as T. basicola and as T. terricola var. minor (e.g. IMI 124,876) proved to belong to T. terricola.

 

 

2. Thielavia tetraspora (Lodhi & Mirza) v- Arx

 

Boothiella tetraspora Lodhi & Mirna - Mycologia 54: 217. 1962 = Thielavia tetraspora (Lodhi & Mirna) v. Arx - Genera of Fungi (ed. 2): 1974.

Thielaviella humicola v. Arx & Tariq Mahmood - Trans. Br. mycol. Soc. S1: 611. 1968. [p. 6]

 

Descriptions: Lodhi & Mirza, 1962; von Arx & Tariq Mahmood, 1968.

 

Cultures studied: CBS 334.67 and CBS 150.68, isolated from soil, India and Pakistan.

 

Thielavia tetraspora can be distinguished from other Thielavia species by the colourless wall of the ascomata, by cylindrical, 4-spored asci and by hyaline, quickly expanding colonies. This species is the type of the genera Boothiella and Thielaviella; it can better be combined with Thielavia, as in T. basicola the wall of the ascomata is also light and translucent. The closely related species T. octospora and T. hyalocarpa also have cylindrical, though 8-spored asci.

 

 

3. Thielavia octospora (Natarajan) v. Arx, comb. nov.

 

Thielaviella octospora Natarajan - Proc. Ind. natn. Sci. Acad., Ser. B., 37: 128. 1971 (basionym).

 

This species is described as having ascomata surrounded by a thick weft of yellow hyphae, cylindrical, 8-spored asci and nearly spherical ascospores, 1o-12 m in diameter, with a distinct germ pore. No material was available for study.

 

 

4. Thielavia hyalocarpa v. Arx, sp. nov. - Fig. 2; Pl. 1a

 

Coloniae 24C in dies 8-10 mm crescunt, albae vel saepe aureae tomentosac, e hyphis hyalinis, 2.5-5 m, crassis compositae. Ascomata dispersa, superficialia vel immersa, sphaerica, translucentia, primum alba vel flava, levia vel tomentosa, non-ostiolata, 350-600 m diam., pariete translucido, 7-10 m crasso e 2-3 stratis cellularum applanatarum, hyalinarum vel flavarum, 3-5 m crassarum composito (textura epidermoidea); capilli myceliales hyalini, septati, 2.5-3.5 m crassi, ad 500 m longi; asci cylindrici vel elongate ellipsoidei, breviter sed distincte stipitati, sursum rotundati octospori, 70-l00 x 11-18 m, maturitate evanescentes; ascosporae plerumque uniseriatae, late fusiformes, uno extremo poro germinationis praeditae, primum hyalinae, deinde obscure brunneae, pariete levi ad extrema modice inspissato et obscurato, 22-26 x 12-14 um. Status conidialis abest.

Typus CBS 322.70, isolatus e terra, Z-Flevoland in Neerlandia, 1970.

 

Colonies on oatmeal-agar at 24C with a daily growth rate of 8-to mm, aerial mycelium white, often forming white or orange-yellow tufts, composed of 2.5-5 m wide, hyaline, septate hyphae; initials arise laterally on the hyphae as coiled branches, soon forming dense clusters composed of 3-S m wide hyphal cells; ascomata dispersed, superficial or immersed in the mycelial mat, spherical, white or yellow when young, smooth or tomentose, non-ostiolate, 350-600 m in diameter, with a translucent, 7-10 m thick wall composed of 2-3 layers of flattened, hyaline or yellow, 3-5 m wide cells (textura epidermoidea); mycelial hairs hyaline, septate, [p. 7] 2.5-3.5 m wide, up to 500 m long; asci cylindrical or elongated ellipsoidal, with a short but distinct stalk, rounded above, 8-spored, 70-100 x 11x18 m evanescent at maturity; ascospores usually uniserate, broadly fusiform, at one end with a distinct germ pore, at first hyaline, becoming dark brown, with a smooth, at the ends slightly thickened and darkened wall, 22-26 x 12-14 m; germ pore round, 1-1.5 m in diameter; conidial state absent.

Type: CBS 322.70, isolated from soil, Z-Flevoland, Netherlands, 1970.

 

 

Fig. 2. Thielavia hyalocarpa. A. part of the ascoma wall; b. part of a mycelial hair; c. ascospores.

 

This species has been in the CBS collection since 1970 as Boothiella spec. It is close to T. tetraspora, but can easily be distinguished by the characters given in the key. On potato-carrot-agar the ascomata usually are smaller and contain only a small number of ellipsoidal asci. Very rarely ascospores were observed with a septum near the end opposite the germ pore, separating a small, hyaline, appendage-like cell. Such ascospores indicate a relationship to genera such as Zopfiella and Echinopodospora in the Sordariaceae.

 

 

5. Thielavia pseudomaritima Davidson

 

Thielavia pseudomaritima Davidson - Trans. Br. mycol. Soc. (in press)

 

This fungus can be recognized by spherical, non-ostiolate, 250-350 m sized ascomata with a translucent wall composed of a few layers of hyaline hyphal cells. The irregularly disposed asci are obovate or broadly clavate, 8-spored and evanescent. The ascospores are ovate or nearly spherical, smooth, thick-walled, green brown when mature, measure 16-20 x 15-19 m and have a distinct germ pore at one end.

The fungus was observed by Dr. D. E. Davidson on incubated stems [p. 8] of Scarcobatus vermiculatus, collected in Bamforth saline lake in Wyoming, U.S.A. A part of the type could be studied; germinating ascospores, however, could not be observed and no pure cultures could be received.

T. pseudomaritima is close to T. tetraspora and T. hyalocarpa, but both species can be distinguished by cylindrical asci and by the size and shape of the ascospores.

 

 

6. Thielavia terricola (Gilman & Abbott) Emmons - Pl. 1b

 

Coniothyrium terricola Gilman & Abbott - Iowa St. Coll. J. Sci. 1: 267. 1927 = Thielavia terricola (Gilman & Abbott) Emmons - Bull. Torrey bot. Club S7: 124. 1930.

 

This common species can be recognized by the formation of a white mycelial mat, by spherical ascomata with a light brown wall composed of textura epidermoidea, by elongated obovate asci and by ellipsoidal or slightly fusiform ascospores, usually 12-16 x 7-9 m in size, with a distinct germ pore at one end.

 

Cultures studied: CBS 537.50, CBS S39.50, CBS 540.50 (all received as T. basicola), CBS 165.71, CBS 752.71, CBS 165.73 and some other isolates from dung, seed, soil and other substrates (see CBS, List of Cultures, 1972).

 

A detailed study of this species has been published by Doguet (1956).

 

 

7. Thielavia peruviana (Gouchenauv) Malloch & Cain - Pl. 1d

 

Chaetomidium peruvianum Gochenaur - Mycologia 60: 1118. 1968 = Thielavia peruviana (Gochenaur) Malloch & Cain - Mycologia 65: 1067. 1973.

 

This species is only known from the type strain (CBS 732.68). It can be recognized by small ascomata, 75-130 m in diameter, covered with cylindrical, septate, brown, 10-150 m long and 2.5-4.5 m wide, blunt setae. The ascospores are fusiform, measure 15-17 x 5-6 m and have a very distinct (up to 2 m wide) germ pore.

 

T. appendiculata can easily be distinguished from T. peruviana by ellipsoidal ascospores with a subapical germ pore.

 

 

8. Thielavia fragilis (Natarajan) v. Arx, comb. nov. - Pl. 1c

 

Chaetomidium fragile Natarajan - Proc. Ind. natn. Sci. Acad., Ser. B., 37: 124. 1971 (basionym).

 

This species has spherical, light brown ascomata with a 5-8 m thick [p. 9] wall, composed of textura epidermoidea of flattened, brown, 2.5-5 m wide cells. The ascomata may be smooth or covered with some very long, brown, towards the end hyaline, 2-3 m wide hairs. The ascospores are rather irregular in shape, but are often nearly clavate or obovate, rounded at one end, attenuated and provided with a distinct germ pore at the other, 11-14 x 6-7 m in size.

 

The fungus is only known from the type strain (CBS 456.73), isolated from the rhizosphere of Pennisetum typhoides in India.

 

 

9. Thielavia variospora Cain

 

Thielavia variospora Cain - Can. J. Bot. 39: 1234.1961.

 

Descriptions: Cain, 1961; Horie and Udagawa, 1973.

 

The species is very close to T. terricola and can be distinguished only by its irregularly shaped, but mostly ellipsoidal or ovate ascospores, 9-15 x 5-9 m in size. No material was available for study.

 

 

10. Thielavia microspora Mouchacca

 

Thielavia microspora Mouchacca - Bull. trimest. Soc. mycol. Fr. 89: 300. 1973.

 

Colonies on oatmeal-agar with a daily growth rate of 3-4 mm at 30C, soon becoming greyish-brown; aerial mycelium composed of hyaline or brownish, septate, sometimes verrucose, 1.5-3 m wide hyphae; ascomata spherical, non-ostiolate, 50-200 (-350) m in diameter, with a 3-6 m thick wall (textura epidermoidea), composed of brown, flattened, 2-5 m wide hyphal cells, surrounded by a weft of brown, septate, branched, often appendage-like, 1.5-3 m wide hyphae; asci obovate or ellipsoidal, evanescent, 8-spored, 15-25 x 10-15 m; ascospores broadly fusiform or ellipsoidal, at one end with a rather distinct germ pore, at the other end often slightly apiculate, brown when mature, with a rather thick wall, 8-10 x 5.5-6.5 m; chlamydospores lateral, terminal or intercalary on the aerial hyphae, clavate, ellipsoidal or roundish, hyaline, 4-10 x 3-5 m.

 

Cultures studied: CBS 808.73, received from A. F. Moustafa and CBS 276.74, type strain, sent by J. Mouchacca, both isolated from desert soil.

 

 

11. Thielavia minuta (Cain) Malloch & Cain

 

Chaetomidium minutum Cain - Can. J. Bot. 39: 1233. 1961 = Thielavia minuta (Cain) Malloch & Cain - Mycologia 65: 1066. 1973.

 

Description: Cain, 1961. [p. 10]

 

No cultures of this species could be studied.

 

 

12. Thielavia australiensis Tansey & Jack - Pl. 1f

 

Thielavia australiensis Tansey & Jack - Can. J. Bot. (in press).

 

The type strain (CBS 493.74) of this thermophilic species shows optimal growth at temperatures of 35-40C. The colonies are white and lanose; the usually smooth ascomata are spherical, 90-230 m in diameter and have a light brown or straw-coloured, 6-9 m thick wall, composed of irregularly shaped, flattened, 5-8 m broad, up to 20 m long cells (textura epidermoidea). The ascospores are pyriform or nearly triangular in planar view, thick-walled, brown, 6-8 x 5-6 m, with a germ pore at the attenuated end. No conidia could be observed.

 

 

13. Thielavia terrestris (Apinis) Malloch & Cain

 

Allescheria terrestris Apinis - Nova Hedwigia 5: 68. 1963 = Thielavia terrestris (Apinis) Malloch & Cain - Can. J. Bot. 50: 66. 1972.

 

Descriptions: Apinis, 1963; Malloch and Cain, 1973; Minoura et al., 1973.

 

No ascomata could be observed in the type strain. The aerial mycelium is composed of hyaline or light brownish, regularly septate, 2-4 m broad hyphae with often partly swollen cells. The conidiogenous cells arise as short, lateral branches on the hyphae and may elongate during the formation of the conidia. The conidia are broadly clavate, obovate or pyriform, with a truncate base, 1-celled, hyaline, 3-6 x 2-3 m, and are borne singly, in basipetal succession or in indistinct sympodulae.

Ascomata developed in CBS 492.74 on malt-agar at 36C beneath the lanose mycelial mat. They are spherical or slightly flattened, usually smooth, black, 140-280 m in diameter, with an 8-10 m thick wall composed of thick-walled, dark brown, 2-3 m broad, irregularly interwoven hyphal cells (loose textura epidermoidea). The asci develop in fascicles from croziers, are clavate, stalked, 8-spored, 20-27 x 9-12 m, evanescent. The ascospores are ovate or pyriform, brown, thick-walled, contain 1-2 droplets, have a distinct germ pore at the attenuated end and measure 5.5-7 x 4-5.5 m.

The conidial state may be close to genera such as Scopulariopsis and especially Scedosporium and this points to a relationship with the Microascaceae.

 

Cultures studied: CBS 355.66, type strain, isolated from pasture soil, sent by A. E. Apinis; CBS 492.74 = HUT 4081, isolated from soil, sent by K. Minoura. [p. 11]

 

 

14. Thielavia coactalis Nicot

 

Thielavia coactalis Nicot in Nicot & Longis - C.r. hebd. Sanc. Acad. Sci. 253: 304. 196.

 

Description: Nicot and Longis, 1961.

 

No material of this species was available; subcultures of the type strain (CBS 352.62) proved to contain T. hyrcaniae and were discarded.

 

 

15. Thielavia appendiculata Srivastava & al. - Pl. 1e

 

Thielavia appendiculata Srivastava & al. - Mycopath. Mycol. appl. 30: 205. 1966.

 

Colonies on oatmeal-agar at 25 C with a daily growth rate of 3-4 mm, white, in age yellow, composed of septate, hyaline, 2.5-4 m wide hyphae; ascomata spherical, non-ostiolate, brown, 75-160 m in diameter, with a thin wall, consisting of 2.5-3.5 m wide, brown or yellow hyphal cells (textura epidermoidea), covered with septate, slightly attenuated, brown, verrucose, 10-30 m long and 2-3.5 m wide appendages; asci usually obovate, evanescent, 24-32 x 11-15 m, 8-spored; ascospores ellipsoidal or slightly fusiform, brown, 13-17 x 7-10 m, with a distinct subapical germ pore.

 

Cultures studied: CBS 723.68, type strain, isolated from leaves of Punica granatum; CBS 731.68, isolated from dung by H. K. Seth; CBS 417.73, received from J. N. Kapoor (New Delhi).

 

 

16. Thielavia hyrcaniae Nicot - Pl. 1g, h

 

Thielavia hyrcaniae Nicot in Nicot & Longis - C.r. hebd. Sanc. Acad. Sci. 253: 305. 1961.

 

Colonies on oatmeal-agar at 25 C with a daily growth rate of 2-3 mm, at first whitish, soon becoming brownish green or olivaceous; ascomata spherical, non-ostiolate, 75-150 m in diameter, with a brown wall of textura epidermoidea, covered with undulate, unbranched, septate, verrucose, brown, apically hyaline, up to 120 m long, 2-3.5 m wide hairs; asci ovate or ellipsoidal, 35-40 x 13-17 m, mostly 6-8-spored; ascospores ellipsoidal fusiform, 12-16 x 6-8 m, often inequilateral, green-brown, with a subapical, very conspicuous germ pore.

 

Cultures studied: CBS 352.61, type strain, isolated from soil in Iran; CBS 753.71, isolated from dung in India by B. C. Lodha. [p. 12]

 

 

17. Thielavia subthermophila Mouchacca

 

Thielavia subthermophila Mouchacca - Bull. trimest. Soc. mycol. Fr. 89: 297. '973.

 

The species shows its optimal growth rate at about 36C and forms dark grey colonies with a dense aerial mycelium and a black reverse. Conidia (aleuriospores, chlamydospores), formed laterally or terminally on the hyphae or on short branches, are broadly clavate or pyriform, with a truncate base, 1-celled, hyaline or light brown and measure 4-7 x 3-4 m. The ascomata develop in the mycelial mat and are spherical, black, 90-200 m in diameter. The thin, dark wall of the ascomata is composed of textura epidermoidea or of flattened, in outline irregular, 5-8 m sized cells and is often covered with dark hyphae. The ascospores are fusiform or ellipsoidal, 1-celled, brown, 14-19 x 8-10 m, with a distinct, subapical germ pore.

 

Cultures studied: CBS 509.74, type strain, CBS 550.74, both isolated from desert soil, Egypt, sent by J. Mouchacca.

 

T. subthermophila is very close to T. arenaria, but can be distinguished by the size of the ascospores. Both species are peculiar by the formation of dark colonies with a black reverse and their thermophilic properties.

 

 

18. Thielavia arenaria Mouchacca

 

Thielavia arenaria Mouchacca - Bull. trimest. Soc. mycol. Fr. 89: 295. 1973.

 

This species is close to T. subthermophila and can be distinguished mainly by smaller ascospores, 8-12 x 5-6.5 m in size. The ascomata with a diameter of 60-120 m have a wall of textura epidermoidea and are covered by dark hyphae. The conidia (chlamydospores), borne laterally, terminally or intercalarily on the aerial hyphae, are spherical or broadly clavate, hyaline or light brown, thin-walled and measure 4-8 x 3-5 m.

 

Cultures studied: CBS 507.74, type strain and CBS 508.74, isolated from desert soil, Egypt, sent by J. Mouchacca.

 

Potato-carrot-agar proved to be a suitable medium for the production of ascomata; cultures on cornmeal or oatmeal-agar remained sterile.

The strain CBS 945.72, isolated from desert soil in Kuwait, sent by A. F. Moustafa, has been identified tentatively as T. arenaria. The ascospores in this strain are ellipsoidal or fusiform, dark brown, measure 9-12 x 6-7 m and have a very conspicuous subapical germ pore. Conidia (chlamydospores) were also observed, but the colonies are light and show an optimal growth rate at temperatures of about 27 C. [p. 13]

 

 

Excluded species of Thielavia

 

A large number of species to be excluded from Thielavia were already enumerated by Malloch and Cain (1973). Other species, partly accepted by these authors as Thielavia will be classified elsewhere in this paper in the following genera: Chaetomidium (7 species), Melanocarpus (1 thermophilic species), Corynascus (5 species) and Coniochaetidium (2 species).

The following species, accepted by Malloch and Cain (1973) should also be excluded:

 

Thielavia magna (Bainier) Malloch & Cain - Mycologia 65: 1065. 1973 = Chaetomidium magnum Bainier - Bull. trimest. Soc. mycol. Fr. 25: 194. 1909.

Thielavia phyllactinea (Bainier) Malloch & Cain - I.c. p. 1067 = Chaetomidium phyllactineum Bainier - l.c. p. 193.

Both species are only known by the rather incomplete description. Neither herbarium specimens not cultures are available.

 

Thielavia neocaledonensis C. Moreau ex Huguenin - Bull. trimest. Soc. mycol. Fr. 81: 699. 1965 (1966).

 

This species is described as having light, translucent ascomata, elongated, evanescent asci and fusiform, finely ornamented ascospores with two apiculate germ pores. The fungus may belong to Melanospora (Microthecium), as it possibly is related to Melanospora hypomyces (Hhnel) Doguet. No material could be studied.

 

Thielavia leptoderma Booth - Mycol. Pap. 83: 3. 1961.

Malloch & Cain (1973) introduced for this species the new genus Aporothielavia. In its morphological characters, Aporothielavia leptoderma is much like Zopfiella curvata (Fuck.) Wint. (NHL 2694 = CBS 591.74). Distinguishing characters of both Zopfiella curvata and Aporothielavia leptoderma are the non-ostiolate ascomata with a cephalothecoid wall composed of plates of radiating cells, often covered with a few very long, septate, dark, smooth hairs, the broadly clavate or nearly spherical asci and the ascospores which are asymmetrical, nearly falcate, 16-22 x 5-6 m in size. In Zopfiella curvata the ascospores become septate near the base, the small basal cell remains hyaline, the large upper one becomes pigmented and may be divided again by a secondary cross wall (Udagawa and Horie, 1974). The upper cell has a subapical germ pore. In IMI 54770 = CBS 538.74, the type strain of Aporothielavia leptoderma, the ascospores have the same shape and size, but remain one-celled and become brown in age. A subapical germ pore, as described by Booth (1961) could not be observed.

Aporothielavia leptoderma (Booth) Malloch & Cain, a species known by a single strain, may represent a form of Zopfiella curvata with delayed growth, forming one-celled ascospores without germ pore. [p. 14]

The following Thielavia species have been published after completion of this manuscript and could not yet be studied:

 

Thielavia wareingii Seth - Nova Hedwigia 25: 468. 1974.

Collected on rabbit dung; characterized by spherical ascomata covered with short appendages and by ovate ascospores with one or two germ pores, 8-14 x 6-9 m. According to the description probably identical with T. appendiculata.

 

Thielavia kirilenkoae Beljakova - Mikol. Fitopatol. 8: 73. 1974.

Isolated from roots of Avena sativa, with optimal growth at about 37C, described as having small, smooth ascomata and ellipsoidal ascospores, 8-10 x 5-6.5 m in size, with a single germ pore, and forming aleurioconidia, 4-7 m in size. According to the description and the figures this species may be identical with T. microspora.

 

Thielavia inaequalis Pidoplichko & al. - Mikrobiol. Zh., Kiev ,3S: 723 1973.

Isolated from soil, characterized by small ascomata with short appendages, clavate asci and ellipsoidal ascospores, 13-16 x 6-8 m in size, with two germ pores (!). According to the description close to T. appendiculata, probably identical with this species.

 

Thielavia ovispora Pidoplichko & al. - l.c. p. 724.

Isolated from soil, characterized by small, smooth ascomata, clavate asci and ovate ascopores, 8-9.5 x 4.5-6 m. Probably close to T. minuta.

 

Thielavia pallidospora Pidoplichko & al. -1c. p. 725.

Characterized by spherical, dark ascomata, 75-150 m in diameter, ovate, light coloured, 5.5-7.5 x 5-5.5 m sized ascospores with two germ pores and by the formation of clavate, hyaline conidia, 7-10 x 4-6 m in size. This species may be belong to the genus Petriellidium and may be identical with P. ellipsoideum v. Arx & Fassatiov (von Arx, 1973).

 

 

Chaetomidium (Zopf) Sacc.

 

Chaetomium subg. Chaetomidium Zopf - Nova Acta K. Leop. Carol. Dt. Akad. Naturf. 42: 280. 1881 = Chaetomidium (Zopf) Sacc. - Syll. Fung. 1: 39. 1882.

 

Colonies spreading, soon becoming green-brown or grey, composed of septate, branched, usually pigmented hyphae; ascomata borne on the hyphae, superficial, spherical, non-ostiolate, with a pseudoparenchymatous wall composed of isodiametric or flattened, brown, thick-walled cells, covered with straight, undulate or circinate, pigmented hyphal hairs; asci clavate, stipitate, fasciculate, 8-spored, with a thin, deliquescent wall; [p. 15] ascospores limoniform, umbonate at both ends, laterally flattened, 1-celled, brown, with a rather inconspicuous germ pore at the base; conidial states mostly absent.

Type species: Chaetomidium fimeti (Fuckel) Sacc.

 

The genus Chaetomidium is related to Chaetomium and can be considered as the non-ostiolate counterpart of the latter. Other distinguishing characters are the thick, pseudoparenchymatous wall of the ascomata and the laterally slightly flattened ascospores. Chaetomidium shows no direct relationship to Thielavia; intermediates are unknown.

 

 

Key to the species

 

1a.

Wall of the ascomata cephalothecoid, i.e. with sutures and long appendages; conidia present

C. cephalothecoides

1b.

Wall of the ascomata not cephalothecoid

2

 

 

 

2a.

Ascospores 5-7 m long

C. spirotrichum

2b.

Ascospores 8-18 m long

3

 

 

 

3a.

Ascospores 8-10 m long

C. subfimeti

3b.

Ascospores 11-18 m long

4

 

 

 

4a.

Appendages of the ascomata stiff, hypha-like

C. pilosum

4b.

Appendages of the ascomata flexuous, undulate or circinate

5

 

 

 

5a.

Appendages of the ascomata flexuous or undulate

C. fimeti

5b.

Appendages of the ascomata thick at the base, with circinate tips

C. trichorobustum

 

 

1. Chaetomidium fimeti (Fuckel) Sacc.

 

Chaetomium fimeti Fuckel - Enum. Fung. Nass., Ser., 1: 491. 1861 = Chaetomidium fimeti (Fuckel) Sacc. - Syll. Fung. 1: 39. 1882 = Thielavia fimeti (Fuckel) Malloch & Cain - Mycologia 65: 1064. 1973.

 

Description: Malloch and Cain, 1973 (as Thielavia fimeti).

 

Culture studied: CBS 168.71, received from D. Malloch. Other CBS cultures proved to be sterile or are re-identified as Chaetomium globosum Kunze ex Fr.

 

This species is characterized by large, dark ascomata, covered with two kinds of dark, verrucose or smooth, usually 3-6 m wide hairs. The dark, 1-celled ascospores have a thickened or darkened wall at the umbonate ends and measure 11-16 x 10-12 x 8-10 m.

 

 

2. Chaetomidium subfimeti Seth

 

Chaetomidium subfimeti Seth - Trans. Br. mycol. Soc. 50: 46. 1967 = Thielavia [p. 16] subfimeti (Seth) Malloch & Cain - Mycologia 65: 1070. 1973.

Descriptions: Seth, 1967; Malloch and Cain, 1973 (as Thielavia subfimeti).

 

Cultures studied: CBS 370.66, type strain, isolated from paper, sent by H. K. Seth; CBS 169.71, isolated from soil, sent by D. Mallocb.

 

This species differs from all others by smaller ascospores, usually 8-10 x 7-8 x 6-7 m in size. The dark ascomata are covered with two kinds of hairs.

 

 

3. Chaetomidium trichorobustum Seth

 

Chaetomidium trichorobustum Seth - Nova Hedwigia 16: 430. 1968 = Thielavia trichorobusta (Seth) Malloch & Cain - Mycologia 65: 1071. 1973.

 

Description: Seth, 1968.

 

Culture studied: CBS 563.67, type strain, isolated from dung, sent by H. K. Seth.

 

This species can be distinguished from C. fimeti by shorter but wider, apically recurved ascomatal hairs, at the base up to 10 m wide.

 

 

4. Chaetomidium pilosum (Booth & Shipton) v. Arx, comb. nov.

 

Thielavia pilosa Booth & Shipton - Trans. Br. mycol. Soc. 49: 665. 1966 (basionym).

Thielavia californica Malloch & Benny - Mycologia 65: 651. 1973.

 

Descriptions: Booth and Shipton, 1966 (as Thielavia pilosa); Malloch and Benny, 1973 (as Thielavia californica).

 

Cultures studied: CBS 335.67 = IMI 113,231, type strain; CBS 343.73, type strain of Thielavia californica, sent by D. Malloch.

 

The species can be recognized by hypha-like, cylindrical, relatively stiff, verrucose, 3-5 m wide ascomatal hairs. The ascospores have the same shape and size as in C. fimeti. In the type strain of T. californica the ascomatal hairs are somewhat stiffer and darker than in that of T. pilosa; more reliable characters to distinguish the species could not be found.

 

 

5. Chaetomidium spirotrichum (Benjamin) Malloch & Cain

 

Magnusia spirotricha Benjamin - Aliso 3: 199. 1955 = Kernia spirotricha (Benjamin) Benjamin - Aliso 3: 344. 1956 = Chaetomidium spirotrichum (Benjamin) Malloch & Cain - Can. J. Bot. 49: 867. 1971 = Thielavia spirotricha (Benjamin) Malloch & Cain - Mycologia 65: 1069. 1972. [p. 17]

 

Descriptions: Benjamin, 1955; Malloch and Cain, 1971, 1973.

 

Only a few and immature ascomata could be observed in cultures of the type strain (CBS 211.55) and in CBS 828.71, isolated from donkey dung in Israel, sent by E. Mller.

 

 

6. Chaetomidium cephalothecoides (Malloch & Benny) v. Arx, comb. nov.

 

Thielavia cephalothecoides Malloch & Benny - Mycologia 65: 653. 1973 (basionym).

 

Description: Malloch and Benny, 1973.

 

This species was collected on mouse dung. It was studied in culture and showed to have a Botryotrichum- or Staphylotrichum-like conidial state.

 

 

 

Melanocarpus v. Arx, gen. nov.

 

Species thermophilae; coloniae expansae, e hyphis hyalinis, ramosis, septatis compositae; ascomata superficialia, sphaeriea vel modice complanata, non-ostiolata, obscura, pariete pseudoparenchymatico e cellulis applanatis, crassitunicatis brunneis composito; asci obovoidei vel irregulariter rotundati, tenuitunicati, octospori, evanescentes; ascosporae oblatae, ellipsoideae vel ovoideae, applanatae, fuscae, continuae, poro germinationis conspicuo praeditae. Conidia hyalina, continua, crassitunicata, thallica adsunt.

Species typica: Myrioccoccum albomyces Cooney & Emerson.

 

Thermophilic; colonies spreading, light, composed of branched, septate, hyaline hyphae; ascomata superficial, spherical or slightly flattened, nonostiolate, dark, smooth or covered with some undifferentiated hyphae, with a pseudoparenchymatous wall composed of flattened, thick-walled, brown cells; asci obovate or irregularly roundish, thin-walled, 8-spored, evanescent; ascospores oblate, ellipsoidal or ovate, flattened, dark, one-celled, with a de Bary bubble and a distinct germ pore; hyaline, one-celled, large, thick-walled arthroconidia present.

Type species: Myriococcum albomyces Cooney & Emerson.

 

The genus is neither close to Thielavia nor to Chaetomidium. It can easily be distinguished from the latter especially by smooth ascomata and darker ascospores with a distinct, often prominent germ pore, from the former by the pseudoparenchymatous wall of the ascomata and by the oblate ascospores, from both by the formation of arthroconidia.

 

 

1. Melanocarpus albomyces (Cooney & Emerson) v. Arx, comb. nov.

 

Myriococcum albomyces Cooney & Emerson - Thermophilic Fungi: 60. 1964 (basionym) = Thielavia albomyces (Cooney & Emerson) Malloch & Cain - Can. J. Bot. 50: 65. 1972.

 

Descriptions: Cooney and Emerson, 1964 (as Myriococcum albomyces); Malloch and Cain, 1973 (as Thielavia albomyces).

 

Cultures studied: CBS 177.67 = ATCC 16460, type strain, sent by R. Emerson; CBS 268.70 and CBS 747.70, isolated from refuse coal-pit, sent by H.C. Evans.

 

This fungus grows rapidly on oatmeal-agar (and on many other media) at 40C. The black ascomata develop within a few weeks on the lanose, white mycelial mat. They have a diameter of 160-300 m, and their pseudoparenchymatous wall is composed of 2-3 layers of flattened, 10-20 m wide cells. The ascospores are thick-walled, dark-brown when mature, contain a de Bary bubble and measure 13-16 x 11-14 x 9-11 m. The arthroconidia are cylindrical or fusiform with truncate ends or clavate with a truncate base, occasionally Y- or L-shaped, hyaline, rather thick-walled, 22-60 x 6-9 m1 in size.

 

 

Apodus Malloch & Cain

 

Apodus Malloch & Cain - Can. J. Bot. 49: 872. 1971.

 

Colonies restricted in growth, soon becoming dark green-brown, composed of branched, septate, usually pigmented hyphae; ascomata borne from coils on superficial hyphae, spherical, non-ostiolate, with a dark, thick, pseudoparenchymatous wall, composed of several layers of brown, flattened cells, covered with long, dark hyphal hairs; asci elongated, apically attenuated and truncate or rounded, with a refractive, nonamyloid apical structure, basally attenuated and stalked, 8-spored, deliquescent; ascospores ellipsoidal, brown, usually 1-celled, at maturity occasionally with a septum in the middle or the upper or lower third, with a conspicuous germ pore; conidial state absent.

Type species: Apodus deciduus Malloch & Cain.

 

According to Malloch & Cain (1971), the genus is related to Tripterospora Cain = Zopfiella Winter, a genus with ascospores with a small, light appendage-like basal part and a large, dark, usually 1-celled, occasionally septate upper part.

 

 

Key to the species

 

1a.

Ascospores 12-16 x 7-10 m

A. deciduus

1b.

Ascospores 22-27 x 11-14 m

A. oryzae

[p. 19]

 

 

1. Apodus deciduus Malloch & Cain

 

Apodus deciduus Malloch & Cain - Can. J. Bot. 49: 872. 1971.

 

Description: Malloch & Cain, 1971

 

Cultures studied: CBS 506.70, type strain, sent by D. Malloch.

 

This species is characterized by dark ascomata, 150-400 m in diameter, covered with long, dark, flexuous, 4-6 m wide hairs. The ascospores usually are 1-celled, brown, 12-16 x 7-10 m in size, with a single apical germ pore.

 

 

2. Apodus oryzae De Carolis & v. Arx, sp. nov. - Fig. 3; P1. 2a-c

 

Coloniae in agaro farina avenae addita in dies circa 2 mm crescunt (24C), cito obscure viridi-brunneae, e hyphis regulariter et frequenter septatis, dilute pigmentatis, 3-6 m crassis, dense intricatis constant; ascomata superficialia, sphaerica, non-ostiolata, obscure brunnea, 200-500 m diam., pariete 22-45 m crasso e 7-10 stratis cellularum 5-9 m latarum brunnearum, intus clariorum composito, capillis longis, flexis, septatis, dilute pigmentatie, 2.0-2.5 m crassis obtecta; asci e hamis oriuntur, elongati, sursum attenuati et truncati, structura refringente apicali, 3-5 m lata, truncata terminati, breviter pedicellati, octospori, 65-68 x 11-16 m, evanescentes; ascosporae ellipsoideae vel late fusiformes, brunneae, uno poro conspicuo fere in apice disposito, crassitunicatae, strato indistincto hyalino circumdatae, plerumque continuae, raro in medio vel in parte inferiore septatae, 21-27 x 10-14 m; status conidialis abest.

Typus CBS 376.74, isolatus ex vagina Oryzae sativae, Montara in Italia a C. De Carolis.

 

 

Fig 3. Apodus oryzae. a. part of the ascoma wall in cross section; b. ascospores; c. ascus. [p. 20]

 

Colonies on oatmeal-agar at 24C with a daily growth rate of about 2 mm, at first whitish or greyish and lanose, soon becoming dark greenish brown, composed of regularly and frequently septate, light brown or subhyaline, 3-6 m wide hyphae, forming a dense felt; ascomata develop from coiled hyphal branches, superficial, spherical, non-ostiolate, dark brown, 200-500 m in diameter, with a 22-45 m thick wall composed of 7-10 layers of flattened, 5-9 m broad cells, brown in the outer, light in the inner part, covered with long, flexuous, septate, light brown, 2-2.5 m wide hyphal hairs; asci arising from croziers, elongated, apically attenuated and truncate, with a refractive, 3-5 m broad, flat apical structure, at the base attenuated into a short stalk, 8-spored, 65-85 x 11-16 m, evanescent; ascospores ellipsoidal or broadly fusiform, brown, thick-walled, with a single, distinct, slightly subapical germ pore and an indistinct, hyaline sheath, usually 1-celled, rarely septate in the middle or in the lower third, 21-27 x 10-14 m in size; conidial state absent.

Type: CBS 376.74 = RRC 261.72, isolated from sheaths of a rice plant, Montara, Italy, by C. De Coralis in 1972.

 

More than 90% of all ascospores remain 1-celled. The germ pore occurs near the upper end, the septum usually in the lower third, the smaller lower cell often remains somewhat lighter than the upper cell. Occasionally up to 40 m long ascospores could be observed in some subcultures. The wall of the ascomata is composed of several layers, the inner cells being flattened, the outer ones often nearly spherical.

 

 

Corynascus v. Arx

 

Corynascus v. Arx - Proc. K. ned. Akad. Wet., Ser. C, 76: 295. 1973.

 

Mesophilic or thermophilic; colonies spreading, white or light coloured, composed of septate, branched, usually hyaline hyphae; ascomata superficial, often covered by aerial hyphae, spherical, non-ostiolate, small, glabrous or setose, wall composed of irregular, thick-walled, dark, usually flattened, often elongated cells, ornamented with small ridges; asci obovate or nearly spherical, with a thin, evanescent wall, 8-spored; ascospores ellipsoidal or broadly fusiform, 1-celled, brown when mature, at both ends with a distinct germ pore; conidial state Chrysosporium (Sepedonium) with 1-celled, hyaline, smooth or ornamented aleuriocondia.

Type species: Thielavia sepedonium Emmons.

 

The genus Corynascus may be considered as the non-ostiolate counterpart of Achaetomiella v. Arx. It also is similar to Melanospora. The nonostiolate species of the latter genus are classified in the genus Microthecium Corda by Udagawa and Cain (1969): it can be distinguished from Corynascus by the light, translucent wall of the ascomata, by the absence of Chrysosporium conidial states and by darker, occasionally ornamented ascospores.

 

 

Key to the species

 

1a.

Thermophilic, heterothallic; ascospores 22-32 x 17-23 m

C. thermophilus

1b.

Mesophilic, often thermotolerant, homothallic; ascospores smaller

2

 

 

 

2a.

Conidia finely echinulate, conidiogenous cells swollen

C. sepedonium

2b.

Conidia smooth

3

 

 

 

3a.

Ascomata with brown appendages

C. setosus

3b.

Ascomata glabrous

C. novoguineensis

 

 

1. Corynascus sepedonium (Emmons) v. Arx

 

Thielavia sepedonium Emmons - Bull. Torrey bot. Club S9: 417. 1932 = Corynascus sepedonium (Emmons) v. Arx - Proc. K. ned. Akad. Wet., Ser. C, 76: 292. 1973.

Thielavia sepedonium var. minor Mehrotra & Bhattachajee - Antonio van Leeuwenhoek 32: 391. 1966.

Thielavia lutescens Kamyschko - Nov. Sist. niz. Rast. 1965: 116.

 

Descriptions: Malloch and Cain, 1973; Mouchacca, 1973 (both as Thielavia sepedonium).

 

Cultures studied: Besides the type strains of Thielavia sepedonium (CBS 340.33), of the var. minor (CBS 111.69) and of Thielavia lutescens (CBS 632.67), about 10 strains were studied, most of which were isolated recently.

 

Strains of this species often show a great variation in the size and shape of the ascospores and the conidia (Mouchacca, 1973). The ascomata have a diameter of 50-120 m, and their wall is composed of a layer of flattened, 4-8 m wide, up to 20 m long cells with an irregular outline, the brown outer cell wall is ornamented with small ridges. In typical strains the ascospores are ellipsoidal or broadly fusiform and measure 15-19 x 8-10 m. The conidia are spherical, finely echinulate, nearly hyaline and 8-12 m in diameter.

Strains isolated from sandy or desert soil usually deviate by shorter ascospores. In CBS 213.74, recently isolated from soil from Senegal, the ascospores proved to be nearly limoniform and 10-15 x 8-11 m in size. In some ascospores a third, lateral, prominent germ pore could be observed. The variety minor has been proposed to accomodate strains with smaller ascospores, but this has not been accepted by Mouchacca (1973) and by Malloch and Cain (1973). [p. 22]

 

 

2. Corynascus setosus (Dade) v. Arx, comb. nov.

 

Thielavia setosa Dade - Trans. Br. mycol. Soc. 21: 20. 1938 (basionym).

 

Descriptions: Dade, 1938; Doguet, 1956; Horie and Udagawa, 1973.

 

Culture studied: CBS 954.68, isolated from rabbit dung, sent by H. K. Seth. In CBS 332.37, the type strain, only Aspergillus flavus could be observed.

 

This species can be recognized by dark, setose ascomata, 120-220 m in diameter, and by ascospores which are broadly fusiform or limoniform, dark, 17-20 x 11-13 m, and have 2 often prominent germ pores.

 

 

3. Corynascus novoguineensis (Udagawa & Horie) v. Arx

 

Thielavia novoguineensis Udagawa & Horie - Bull. natn. Sci. Mus., Tokyo 15: 191. 1972 = Corynascus novoguineensis (Udagawa & Horie) v. Arx - Proc. K. ned. Akad. Wet., Ser. C., 76: 292. 7973.

 

Description: Udagawa and Horie, 1972.

 

The type strain (CBS 354.72) was studied. This species differs from Corynascus setosus by smaller, glabrous ascomata and by ellipsoidal or fusiform ascospores, 18-24 x 8-10 m in size. The aleuriconidia are spherical or broadly clavate, nearly hyaline, smooth and 6-10 m in diameter.

 

 

4. Corynascus thermophilus (Fergus & Sinden) v. Klopotek

 

Thielavia thermophila Fergus & Sinden - Can. J. Bot. 47: 7635. 1969 = Corynascus thermophilus (Fergus & Sinden) v. Klopotek - Arch. Mikrobiol. 98: 366. 1974.

 

Conidial state: Chrysosporium fergusii v. Klopotek.

 

Descriptions: Fergus and Sinden, 1969; Hedger and Hudson, 1970; von Klopotek, 1974.

 

Cultures studied: CBS 405.69, type strain and CBS 406.69, mating types, isolated from mushroom compost, sent by C. L. Fergus; CBS 174.70, isolated from wheat-straw compost, sent by H. J. Hudson.

 

In this thermophilic and heterothallic species often only the conidial state can be observed. The aleuriconidia are ellipsoidal or obovate, nearly hyaline and measure 7-12 x 5-8 m. Ascomata developed in mating experiments; they are spherical, black, usually smooth, 150-250 m in diameter. The ascospores are ellipsoidal fusiform, dark brown, with two prominent germ pores, 22-32 X 16-22 m in size. [p. 23]

 

 

Corynascella v. Arx & Hodges, gen. nov.

 

Coloniae expansae, laete coloratae, e hyphis septatis ramosis hyalinis vel brunneolis compositae; ascomata superficialia, sphaerica, non-ostiolata, pariete claro e hyphis intertextis composito, quasi textura epidermoidea, hyphis obscuris, septatis, plerumque rectis quasi appendicibus obteeta; asci fasciculati e hamis oriuntur, late clavati vel obovoidei, pedicellati, ostospori, tenui tunicati, evanescentes; ascosporae ellipsoideae, fere globosae vel reniformes, saepe una parte applanatae, in extremis rotundatae, duobus (ad quattuor) poris germinationis plerumque apicalibus praeditae, pariete obscuro circa poros inspissato, vesiculam `de Bary' magnam continent.

Species typica: Corynascella humicola v. Arx & Hodges.

 

Colonies spreading, light, composed of branched, hyaline or brownish hyphae; ascomata superficial, spherical, non-ostiolate, with a light wall composed of interwoven hyphae, nearly textura epidermoidea, covered with dark, septate, appendage-like, usually straight hyphae; asci fasciculate, borne from croziers, broadly clavate or obovate, stalked, 8-spored, thinwalled, evanescent; ascospores ellipsoidal, nearly spherical or reniform, often flattened at 0ne side, rounded at the ends, 1-celled, containing a large de Bary bubble, with a dark wall, thickened around the 2(-4) usually apical germ pores.

Type species: Corynascella humicola v. Arx & Hodges.

 

The genus Corynascus differs from Corynascella by its fusiform or at both ends umbonate ascospores, by the structure of the wall of the ascomata and by the formation of Chrysosporium-conidia. In Corynascella the ascospores are especially characteristic, having a strikingly thickened wall around the germ pores. The genus is reminescent of Melanocarpus due to the flattened ascospores containing a de Bary bubble.

 

 

1. Corynascella humicola v. Arx & Hodges, sp. nov.. - Fig. 4; Pl. 2d-f

 

Coloniae 33C in dies 4-5 mm crescunt, mycelio aerio albo, saepe floccoso vel lanoso e hyphis septatis, hyalinis, 1-3 m crassis composito nonnunquam hyphis brunneis vel hyphis fasciculatis interspersis; ascomata dispersa vel aggregata, superficialia, globosa vel modice applanata, primum alba, deinde hyphis setiformibus, septatis, brunneis, sursum rotundatis, 70-180 m longis, ad basim 3-4 m crassis obtecta, non-ostiolata, pariete claro, transparente, 7-10 m crasso, e textura epidermoidea laxa cellularum 3-5 m crassarum, applanatarum composito; asci fasciculati e hamis oriuntur cylindricoclavati vel obovoidei, pedicellati, 38-50 x 18-23 m, octospori, evanescentes; ascosporae ellipsoideae, fere globosae vel reniformes, saepe una parte applanatae, leves, obscure brunneae, in extremis, raro etiam in latere poris germinationis praeditae, circa quos paries inspissatus, vesiculam magnam continentes, 13-17 x 9-14 um.

Typus CBS 337.72, isolatus e terra Pedemontana in Carolina septentrionali a C.S. Hodges, 1971.

 

Colonies on oatmeal-agar at 33C with a daily growth rate of 4-5 mm, with a white, often floccose or lanose aerial mycelium, composed of septate, [p. 24] hyaline, 1-3 m wide hyphae, often also with some brown hyphae or hyphal strands; ascomata dispersed or clustered, superficial, spherical or slightly flattened, white when young, soon covered by cylindrical, rather stiff, septate, brown, apically rounded, 70-180 m long, at the base 3-4 m wide hyphae, non-ostiolate, with a light, translucent, 7-10 m thick wall composed of a loose textura epidermoidea of 3-S m broad, flattened hyphal cells; asci fasiculate, borne from croziers, cylindrical clavate or obovate, stalked, 38-50 x 18-23 m, 8-spored, evanescent; ascospores ellipsoidal, nearly spherical or reniform, often flattened at one side, smooth, dark brown, containing a large bubble, 13-17 x 9-14 m in size, at each end with a germ pore, around which the spore-wall is strikingly thickened, very rarely also with 1-2 lateral pores.

Type: CBS 337.72, isolated from Piedmont soil, North Carolina, USA, by C.S. Hodges in 1971, sent as Chaetomidium Spec.

 

 

Fig. 4. Corynascella humicola a. mycelial hairs; b. asci; c. ascospores.

 

The fungus develops on oatmeal-agar at temperatures from 20-40C with an optimum growth rate at 33C; ascomata with mature ascospores were obtained only at 27-33 and not at 36 or at 24C.

Occasionally some blastoconidia with a broad base are formed in the aerial mycelium on tips of hyphal branches. The conidia are broadly clavate, obovate or reniform, usually with a truncate base, 1-celled, hyaline and 4-6 x 1.5-3 m in size. [p. 25]

 

 

Coniochaetidium Malloch & Cain

 

Coniochaetidium Malloch & Cain - Can. J. Bot. 49: 878. 1971.

 

Colonies spreading or rather restricted, becoming grey or brown, often orange or pinkish by an exudate, composed of septate, branched, hyaline or brown hyphae; ascomata borne from superficial hyphae forming coils, spherical, non-ostiolate, glabrous or hairy, with a pseudoparenchymatous or plectenchymatous wall composed of light or dark, isodiametric or flattened cells; asci fasciculate or irregularly disposed, obovate, clavate or cylindrical, evanescent, 4- to 8-spored; ascospores ellipsoidal, fusiform, reniform or oblate, one-celled, smooth, brown or green, with a longitudinal or equatorial, often prominent germ slit; conidia absent or blastic.

Type species: Coniochaetidium ostreum Malloch & Cain.

 

The genus Coniochaetidium has been described by Malloch and Cain (1971) for the non-ostiolate counterparts of Coniochaeta; both genera have been classified in the new family Coniochaetaceae, characterized by unitunicate asci and by 1-celled, pigmented ascospores provided with a germ slit. The type species of the genus Coniochaetidium is characterized by large, dark ascomata with a thick, pseudoparenchymatous wall, and by oblate ascospores. In the other species the ascomata are small and thinwalled and the ascospores are fusiform or reniform.

 

 

Key to the species

 

1a.

Ascospores oblate, with an equatorial germ slit; ascomata thick walled

C. ostreum

1b.

Ascospores fusiform or reniform; ascomata thin-walled, light

2

 

 

 

2a.

Ascospores fusiform, 14-20 x 6-8 m

C. savoryi

2b.

Ascospores reniform, 6-8 x 3-5 m

C. boothii

 

 

1. Coniochaetidium ostreum Malloch & Cain

 

Coniochaetidium ostreum Malloch & Cain - Can. J. Bot. 49: 879. 1971,

 

This species is known by a single strain, isolated from a twig of Larrea divaricata, collected in 1960 in Gila Bend, Arizona, USA. In a subculture sent to the CBS in 1970 (CBS 507.70) no ascomata were formed anymore, only some blastoconidia could be observed in the pinkish or orange mycelial mat. The fungus can be recognized by dark, spherical ascomata, 150-400 m in diameter, with a 30-35 m thick, pseudoparenchymatous, dark wall, by irregularly disposed, evanescent, 8-spored asci and by oblate, brown, 5-8 x 4-5.5 m sized ascospores with an equatorial germ slit. [p. 26]

 

 

2. Coniochaetidium savoryi (Booth) Malloch & Cain

 

Thielavia savoryi Booth - Mycol. Pap. 8,;: 3 1961 = Coniochaetidium savoryi, (Booth) Malloch & Cain - Can. J. Bot. 49: 880. 1971.

 

In the type strain (IMI 76,253(b)), isolated from decayed wood of Juniperus scopularum from Wales in 1959, the expanding colonies become orange by the formation of an exudate. The ascomata develop from dense, irregular coils, are spherical, non-ostiolate, 35-70 m in diameter and have a light brown or nearly hyaline wall composed of flattened, irregular, 3-5 m broad cells (textura epidermoidea). Few asci are formed, they contain 4 ascospores and their wall is very evanescent. The broadly fusiform, in cross section ovate ascospores measure 16-21 x 6-7 x 7-8 m, are greenish brown, with a prominent, conspicuous, longitudinal germ slit.

In strain CBS 415.73, recently isolated by G. J. Bollen from soil, the ascospores proved to be laterally more flattened and measured 12-18 x 6-7.5 x 7.5-9 m. No conidia could be observed.

 

 

3. Coniochaetidium boothii (Manoharachary & Ramarao) v. Arx, comb. nov.

 

Thielavia boothii Manoharachary & Ramarao - Trans. Br. mycol. Soc. 61: 196. 1973 (basionym).

 

The type culture (IMI 164,567 = CBS 381.74) was studied. The colonies are pinkish due to the formation of an exudate. The hyphae are hyaline, usually 1.5-3 m wide. On some of the wider hyphae blastoconidia are formed, which are ellipsoidal, ovate or cylindrical, hyaline, 1-celled, 4-8 x 2.5-5 m in size, having a broad base. Larger, often catenulate, hyaline chlamydospores may also be present. The ascomata develop in the mycelial mat, are spherical or irregular in shape, often flattened from above, non-ostiolate and 30-280 m in diameter. Their wall is light brown or nearly hyaline, 4-6 m thick and composed of usually 2 layers of flattened, 3-6 m large, thin-walled cells. The irregularly disposed asci, borne in small fascicles from croziers, are broadly clavate or obpyriform, with a thin, rather persistent wall, 8-spored, 15-24 x 8-13 m in size. The ascospores are ellipsoidal or nearly reniform, 1-celled, already within the asci becoming dark brown and measuring 6-8 x 4-5 x 3-4 m. A germ slit can be observed as an inconspicuous longitudinal rim. [p. 27]

 

 

Ephemeroascus van Emden

 

Ephemeroascus van Emden - Trans. Br. mycol. Soc. 61 : 599. 1973.

 

Colonies restricted in growth, with hyaline aerial mycelium; ascomata superficial or with an immersed base, often confluent into stromatic crusts, spherical, non-ostiolate, dark, glabrous, with a pseudoparenchymatous wall of isodiametric, thick-walled cells; asci irregularly disposed, arising from croziers, obovate or nearly spherical, 8-spored, evanescent; ascospores ellipsoidal or reniform, one-celled, smooth, brown, small, with an inconspicuous, longitudinal germ slit; conidial state phialidic, Verticillium-like, with one-celled, hyaline conidia.

Type species: Ephemeroascus verticillatus van Emden.

 

The relationship of this genus is uncertain. Similar conidial states are known to belong to Nectria and related genera.

 

 

1. Ephemeroascus verticillatus van Emden

 

Ephemeroascus verticillatus van Emden - Trans. Br. mycol. Soc. 61: 601. 1973.

 

Description: van Emden, 1973.

 

Culture studied: CBS 816.71, type strain, isolated from agricultural soil in Wageningen, the Netherlands, 1971.

 

The species is characterized by densely crowded ascomata, often forming dark, stromatic crusts, with a diameter of 50-300 m. The evanescent asci measure 8-10 x 6-8 m and contain 8 usually reniform, laterally slightly flattened, brown ascospores, 4-5 x 2.3-3.5 um. The germ slit can be observed only with difficulty under suitable conditions. The conidia, borne on verticillately arranged, flask-shaped, 8-12 m long phialides, are ovate, one-celled, hyaline, 2-2.5 x 1-1.5 m in size.

 

 

Acknowledgements

 

The author wishes to express his gratidude to Dr Agnes H. S. Onions, Dr K. Minoura, Dr J. Mouchacca and Dr M. R. Tansey for sending cultures. He is indebded t0 Dr N. Lundqvist and Dr D. Malloch for helpful information and comments, to Dr W. Gams and Mr D. Yarrow for reading the manuscript. He thanks Miss J. B. Pannebakker, Miss J. Sytema and Mrs J. H. Brouwer-Zeilmaker for technical assistance.

 

 

References

 

Apinis, A.E., 1963 - Occurrence of thermophilous microfungi in certain alluvial soils near Nottingham. - Nova Hedwigia 5: 57-78.

Arx, J. A. von, 1973a - Ostiolate and non-ostiolate Pyrenomycetes. - Proc. K. ned. Akad. Wet., Ser. C, 76: 289-296.

Arx, J. A. van, 1973b - The genera Petriellidium and Pithoascus (Microascaceae). - Persoonia 7: 367-375.

Arx, J. A. von & Tariq Mahmood, 1968 - Thielaviella humicola gen. et sp. nov. from Pakistan. - Trans. Br. mycol. Soc. 51: 611-613.

Benjamin, R. K., 1955 - An addition to the genus Magnusia. - Aliso 3: 199-201.

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

Booth, C. & Shipton, W. A. 1966 - Thielavia pilosa sp. nov., with a key to species of Thielavia. - Trans. Br. mycol. Soc. 49: 665-667.

Cain, R. F., 1961 - Studies of soil fungi III. New species of Coniochaeta, Chactomidium and Thielavia. - Can. J. Bot. 39: 1231-1239.

Cooney, D. G. & Emerson, R., 1964 - Thermophilic Fungi - San Francisco, 188 pp.

Dade, H. A., 1938 - New Gold Coast Fungi 1. - Trans Br. mycol. Soc. 21: 16-28.

Doguet, G., 1955 - Le genre Melanospora. - Botaniste 39: 313 pp.

Doguet, G., 1956 - Le genre Thielavia. - Rev. Mycol., Suppl. colon. 21: 1-21.

Emden, J. H. van, 1973 - Ephemeroascus gen. nov. (Eurotiales) from soil. - Trans. Br. mycol. Soc. 61: 599-601.

Fergus, C. L. & Sinden, J. W., 1969 - A new thermophilic fungus from mushroom compost: Thielavia thermophila spec. nov. - Can. J. Bot. 47: 1635-1637.

Hedger, J. N. & Hudson, H. J., 1970 - Thielavia thermophila and Sporotrichum thermophile. - Trans. Br. mycol. Soc. 54: 497-500.

Horie, Y. & Udagawa, S., 1973 - Two records of Thielavia species from Thailand soil. - Trans. mycol. Soc. Japan 14: 47-51.

Klopotek, A. von, 1974 - Revision der thermophilen Sporotrichum-Arten. - Arch. Mikrobiol. 98: 365-369.

Lodhi, S. A. & Mirza, R. F., 1962 - A new genus of the Eurotiales. - Mycologia 54: 217-219.

Malloch, D. & Benny, G. L., 1973 - California Ascomycetes: four new species and a new record. - Mycologia 65: 648-660.

Malloch, D. & Cain, R. F., 1971 - New cleistothecial Sordariaceae and a new family, Coniochactaceae. - Can. J. Bot. 49: 869-880.

Malloch, D. & Cain, R. F., 1973 - The genus Thielavia. - Mycologia 65: 1055-1077.

Minoura, K., Ochi, K. & Nehira, T., 1973 - Thermophilic filamentous fungi in Japan (2). - Trans. mycol. Soc. Japan 14: 362-366.

Mouchacca, J., 1973 - Les Thielavia des sols arides: Espces nouvelles et analyse gnrique. - Bull. trimest. Soc. mycol. Fr. 89: 295-311.

Nicot, J. & Longis, D., 1961 - Structure des spores et organisation des perithces de deux Thielavia du sol. - C. r. hebd. Scanc. Acad. Sci. 253: 304-306.

Seth, H. K., 1967 - Chaetomidium subfimeti sp. nov. from Wales. - Trans. Br. mycol. Soc. 50: 45-47.

Seth, H. K., 1968 - Chactomidium trichorobustum sp. nov. from Germany. Nova Hedwigia 16: 429-432.

Udagawa, S. & Cain, R. F., 1969 - Notes on the genus Microthecium. - Can. J. Bot. 47: 1915-1933.

Udagawa, S. & Horie, Y., 1972 - A new species of Thielavia and its Chrysosporium conidial state. - Bull. natn. Sci. Mus. Tokyo 15: 191-196.

Udagawa, S. & Horie, J., 1974 - Notes on some Japanese Ascomycetes XII. - Trans. mycol. Soc. Japan 15: 105-112.

 

 

 

Plate 1. Ascospores of a. Thielavia hyalocarpa; b. T. terricola; c. T. fragilis; d. T. peruviana; e. T. appendiculata; f. T. australiensis; g. T. hyrcaniae (all 1200 x); h. scanning electron micrograph of ascospores of T. hycraniae (4000 x).

 

 

Plate 2. a-c. Apodus oryzae; a. ascus; b. ascospores; c. wall of ascoma in cross section; d-f. Corynascella humicola; d. ascospores; e. ascus; f. wall of ascoma with covering hairs. (a, b, d, e, 1200 x; c, f, 325 x).