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Mycologia, 95(5), 2003, pp. 860-864.
© 2003 by The Mycological Society of America

Digitomyces, a new genus of hyphomycetes with cheiroid conidia


Angel Mercado Sierra

     Instituto de Ecología y Sistemática, Ministerio de Ciencia, Tecnología y Medio Ambiente (CITMA), A.P. 8029, Ciudad de La Habana 10800, Cuba

Misericordia Calduch
Josepa Gené 1
Josep Guarro

     Unitat de Microbiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, 43201-Reus, España

Gregorio Delgado

     Instituto de Ecología y Sistemática, Ministerio de Ciencia, Tecnología y Medio Ambiente (CITMA), A. P. 8029, Ciudad de la Habana 10800, Cuba

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 TAXONOMY
 DISCUSSION
 LITERATURE CITED
 

The new anamorphic genus Digitomyces, based on Dictyosporium verrucosum, is proposed. It is characterized by micronematous or semimacronematous conidiophores, integrated or discrete, holoblastic, determinate conidiogenous cells, and olivaceous to pale brown, verrucose, cheiroid conidia, with a truncate basal cell and (2–)3 arms. The new taxon is compared with morphologically similar anamorph genera.

Key words: anamorphic fungi, cheiroid conidia, Cheiromoniliophora, Cheiromycella, Cheiromyceopsis, Cheiromyces, Cheiromycina, Cheiropolyschema, Dictyosporium verrucosum, hyphomycetes, Kamatia, Pseudodictyosporium, Ramoconidiifera, systematics


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 TAXONOMY
 DISCUSSION
 LITERATURE CITED
 
Two strains of a hyphomycete with cheiroid conidia, collected by the authors in Cuba and Mexico, respectively, were identified as Dictyosporium verrucosum Tzean & J.L. Chen. This species first was found in 1987 colonizing a fallen stem collected in Taiwan (Tzean and Chen 1989Citation). Dictyosporium verrucosum has been considered to be an earlier name for Ramoconidiifera verrucosa B. Sutton, Carmarán & A. I. Romero (Sutton et al 1996Citation, Goh et al 1999Citation). Those two strains of Dictyosporium verrucosum have micronematous or semimacronematous conidiophores, integrated or discrete, determinate, monoblastic or polyblastic conidiogenous cells, and verrucose conidia with 2–3 arms that are formed by few cells and inserted at the same level. This morphology of conidiophores and conidia is inconsistent with Dictyosporium Corda or with the morphologically similar but distinct Ramoconidiifera or any other genus. We accordingly propose a new genus for Dictyosporium verrucosum.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
TAXONOMY
 DISCUSSION
 LITERATURE CITED
 
The in vitro colony morphology was studied from cultures grown on potato-carrot agar (PCA: 20 g potatoes, 20 g carrots; 18 g agar, 1000 mL tap water) and oatmeal agar (OA: 30 g oat flakes, 1 g MgSO4·7H2O, 1.5 g KH2PO4, 15 g agar, 1000 mL tap water) incubated at 25 C. Color notations in parentheses are from Kornerup and Wanscher (1984)Citation. Microscopic characteristics were determined in lactic acid. Photomicrographs were obtained by light microscopy (Leitz Dialux 20) and by scanning electron microscopy (Jeol JSM-6400).


   TAXONOMY
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 TAXONOMY
DISCUSSION
 LITERATURE CITED
 
Digitomyces Mercado, Calduch & Gené, gen. nov.


Coloniae in hospite punctiformes vel effusae, pulvinatae, brunneae vel atro-brunneae. Conidiophora solitaria vel sporodochia formantia, micronematosa vel semimacronematosa, mononematosa, non ramosa vel irregulariter ramosa, subhyalina vel pallide brunnea, laevia. Cellulae conidiogenae integratae vel discretae, monoblasticae, nonnumquam polyblasticae, determinatae, cylindricae, doliiformes, globosae vel subglobosae vel capitatae. Conidia solitaria, sicca, cheiroidea, olivaceobrunnea vel pallide brunnea, cellulae basales truncatae, 2–3 brachia ferentes; brachia verrucosa, 0–3-septata, parallele adpressa et in uno plano complanata. Teleomorphosis ignota.

Species typica. Digitomyces verrucosus (Tzean & J. L. Chen) Mercado, Calduch & Gené.


Colonies on host punctiform or effuse, powdery, brown or dark brown. Conidiophores solitary or forming sporodochia, micronematous or semimacronematous, mononematous, simple or irregularly branched, subhyaline to pale brown, smooth. Conidiogenous cells integrated or discrete, monoblastic, occasionally polyblastic, determinate, cylindrical, doliiform, globose, subglobose or capitate. Conidia solitary, dry, cheiroid, olive-brown to pale brown, acropleurogenous, consisting of a truncate basal cell on which 2–3 arms arise parallel and appressed, conidia flattened in one plane; arms verrucose, 0–3-septate. Teleomorph unknown.

Digitomyces verrucosus (Tzean & J. L. Chen) Mercado, Calduch & Gené, comb. nov. Figs. 1–6.



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  		FIGS. 1–6. Digitomyces verrucosus, HACM 9838. 1, 2, 4–6. Conidiophores, conidiogenous cells and conidia on PCA at 25 C. 3. Conidia from natural substratum. Bars: 1, 2, 4–6 = 10 µm; 3 = 5 µm

 

Basionym: Dictyosporium verrucosum Tzean & J. L. Chen, Mycol. Res. 92: 497. 1989.

Colonies on the natural substratum punctiform or effuse, powdery, olive-brown, brown or dark brown. Mycelium mostly immersed, composed of subhyaline, septate, branched, smooth hyphae. Conidiophores borne directly on the mycelium, smooth and thick-walled, flexuous, 5–15(–20) x 3–5.5 µm. Conidiogenous cells mostly cylindrical, doliiform or sphaeroid, pale olivaceous-brown to brown, smooth-walled, sometimes crooked, bearing one or more conidia, 3.5–15 x 3–6 µm. Conidia pale brown to pale golden-brown to olive-brown, (12–)14–18(–22) x (10–)11–15(–18) µm, consisting of 5–9 cells arranged on a truncate basal cell, 3–5.5 µm wide, with (2–)3 slightly incurved arms; arms 1–3-septate rounded at the apex, 9–16 x 4.5–6 µm, strongly verrucose, especially on the last two cells of each arm, verrucae 0.5–1 µm high.

Specimens examined. CUBA. SANCTI SPIRITUS PROVINCE: Sierra del Escambray, Topes de Collantes, on the road to Finca Codina, on a dead branch of Ocotea nemodaphne Mez, 30 Mar 2000, G. Delgado (HACM 9838). MEXICO. VERACRUZ: on dead branches of an unidentified tree, 19 Mar 1996, A. Mercado (HACM 9839; living cultures IMI 389646, CBS 111143, FMR 7828).

Colonies on PCA 35–39 mm diam after 21 d, slightly velvety, flat, dark brown (M 9F8) at the center, reddish brown (M 8D5–8E6) toward the periphery, margin predominantly with subhyaline submerged mycelium; reverse brown to dark brown (M 7E7–7F8) at the center, golden-yellow (M 5B7) at the periphery. A grayish-yellow (M 4B3–4B6) to grayish-orange (M 5B4–5B6) soluble pigment diffusing through the medium. Colonies on OA 34–36 mm diam after 21 d, velvety, flat, medium gray to dark gray (M 1E1–1F1) at the center and dark brown (M 8F8–9F8) toward the periphery, margin with grayish aerial mycelium and subhyaline submerged mycelium; reverse dark brown (M 9F8). Soluble pigment absent. On both media, the conidiophores usually arising from bundles of aerial hyphae. In vitro morphology of conidiophores and conidia not differing from that on natural substratum.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 TAXONOMY
 DISCUSSION
LITERATURE CITED
 
Sutton (1985)Citation reviewed some genera with cheiroid or digitate brown conidia, including Dictyosporium, in which 19 species were accepted. Later Sutton et al (1996)Citation provided a key to some hyphomycetous genera with this kind of conidia and confined Dictyosporium to species with smooth-walled conidia. In a more recent revision of Dictyosporium, Goh et al (1999)Citation, following criteria adopted by Sutton et al (1996)Citation, accepted 22 species and excluded D. verrucosum. They considered this as synonymous with Ramoconidiifera verrucosa (Sutton et al 1996Citation). Our specimens match the protologue of D. verrucosum, except for the presence of polyblastic conidiogenous cells. However, neither collection produced percurrently proliferating conidiogenous cells on unbranched macronematous conidiophores, features that are diagnostic of Ramoconidiifera. Thus we do not accept the synonyms of Dictyosporium verrucosum and Ramoconidiifera verrucosa and consider that D. verrucosum represents a new genus of hyphomycetes. The genera morphologically closest to Digitomyces are Ramoconidiifera and Cheiromycella Höhn, according to the key given by Sutton et al (1996)Citation. However, in addition to the differences mentioned above, the conidia of Ramoconidiifera are pigmented unevenly (brown basal cell and paler arms), the verrucae are limited to the apical cell of each arm and the arms are inserted at different levels. Cheiromycella and Digitomyces both have mono- or polyblastic conidiogenous cells and sporodochial conidiomata, but the conidia in the former always are smooth and constricted at the septa, mostly with two arms, and conidiophores are macronematous and moniliform, i.e., frequently having bulbous cells connected by narrow isthmi (Ellis 1971Citation).

Other genera resembling these three genera are Cheiromoniliophora Tzean & J. L. Chen, Cheiromyceopsis Mercado & J. Mena, Cheiromyces Berk. & M. A. Curtis and Cheiropolyschema Matsush. The key features for distinguishing these and other genera with cheroid conidia from Digitomyces are summarized in Table I.


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  		TABLE I. Diagnostic features of morphologically similar cheiroid hyphomycetes

 

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  		TABLE I. Continued

 


   ACKNOWLEDGMENTS
 
The authors are indebted to Enrique Descals (IMEDEA, CSIC/UIB) for his helpful comments. This work was supported by Fundació Ciència i Salut (Reus, España) and by the Darwin Initiative (U.K.).


   FOOTNOTES
 
1 Corresponding author, Email: jgd{at}fmcs.urv.es Back

Accepted for publication February 3, 2003.


   LITERATURE CITED
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 TAXONOMY
 DISCUSSION
 LITERATURE CITED
 
Bhat DJ, Kendrick WB., 1993 Twenty-five new conidial fungi from the western Ghats and the Andaman Islands (India). Mycotaxon 49:19-90

Castañeda Ruiz RF, Guarro J, Cano J., 1997a Notes on conidial fungi. XI. Two new species of Cheiromoniliophora and Oncopodium. Mycotaxon 61:319-326

Castañeda Ruiz RF, Guarro J, Figueras MJ, Gené J, Cano J., 1997b More conidial fungi from La Gomera, Canary Islands, Spain. Mycotaxon 65:121-131

Ellis MB., 1971 Dematiaceous Hyphomycetes. Kew,. England: Commonwealth Mycological Institute. 608 p

Goh TK, Hyde KD, Ho WH, Yanna, 1999 A revision of the genus Dictyosporium with descriptions of three new species. Fungal Diversity 2:65-100

Ho WH, Hodgkiss IJ, Hyde KD., 2000 Cheiromyces lignicola, a new cheirosporous anamorphic species from Hong Kong. Mycologia 92:582-588

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

Matsushima T., 1971 Microfungi of the Solomon Islands and Papua-New Guinea. Kobe: Published by the author. 78 p

Matsushima T., 1980 . Matsushima Mycological Memoirs 1:1-82

Matsushima T., 1983 . Matsushima Mycological Memoirs 3:1-90

Mercado Sierra A, Mena Portales J., 1988 Nuevos o raros hifomicetes de Cuba II. Un nuevo género sobre Roystonea regia. Acta Botanica Cubana 53:1-5

Rao VG, Subhedar AW., 1976 Kamatia—a new genus of hyphomycetes. Trans Br Mycol Soc 66:539-541

Sutton BC., 1985 Notes on some deuteromycete genera with cheiroid or digitate brown conidia. Proc Indian Acad Sci, Pl Sci 94:229-244

Sutton BC., Carmarán CC, Romero AI., 1996 Ramoconidiifera a new genus of hyphomycetes with cheiroid conidia from Argentina. Mycol Res 100:1337-1340

Sutton BC., Muhr L-E., 1986 Cheiromycina flabelliformis gen. et sp. nov. on Picea from Sweden. Nord J Bot 6:831-836

Tzean SS, Chen JL., 1989 Two new species of Dictyosporium from Taiwan. Mycol Res 92:497-502

Tzean SS, Chen JL., 1990 Cheiromoniliophora elegans gen. et sp. nov. (Hyphomycetes). Mycol Res 94:424-427





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Right arrow Articles by Delgado, G.

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