The identity of Cintractia disciformis: reclassification and synonymy of a southern Asian smut parasitic on Carex sect. Aulocystis

Abstract

The identity of a neglected smut fungus, Cintractia disciformis, described from Carex hirtella in the Western Himalaya, India is reassessed. The species is excluded from Cintractia and is confirmed as a distinct species of Anthracoidea. Two smuts, A. nepalensis on Carexnakaoana in Nepal, and A. haematostomae on Carex haematostoma in China, are similar morphologically and considered to be later heterotypic synonyms of Cintractia disciformis. The appropriate nomenclatural combination for this species, Anthracoidea disciformis comb. nov., is validated.

Introduction

The smut fungus Cintractia disciformis was originally described from a plant identified as Carex hirtella (sect. Aulocystis) collected at Nipchang in Western Himalaya, India. Cintractia disciformis was first invalidly introduced without the mandatory Latin description that was required from 1 January 1935 until 31 December 2011 (Liro 1935). A few years later Liro (1939) provided the missing Latin diagnosis. The species has only occasionally been reported in the literature, for instance in connection with a second finding on Mt. Sawi in Indian Kashmir on a new host, Carex haematostoma (Ling 1949), or in monographic studies on smut fungi (Zundel 1953, Zambettakis 1978, Piepenbring 2000, Vánky 2007a, 2012, Gandhe 2011). Ling (1949) and Zambettakis (1978) prepared descriptions of the Kashmiri specimen of Cintractia disciformis. Other authors have either repeated the description from the protologue (Zundel 1953, Gandhe 2011), or not included one (Piepenbring 2000, Vánky 2007a, 2012). In a monograph of Anthracoidea, Zambettakis (1978) proposed a new combination “Anthracoidea disciformis (Liro) Zambett.”, but without giving any indication of the basionym or any reference to the place of its valid publication, rendering the combination invalid (ICN, Art. 33.4), like all new combinations introduced in that work.

Vánky (2012) examined the type material of Cintractia disciformis in H, and concluded that it was an Anthracoidea. However, he did not accept the species or make any transfer to that genus as he noted that the host Carex was not C. hirtella according to an annotation by I. Kukkonen on the specimen. Vánky commented that “without the correct name of the host plant it cannot be identified”.

Two smuts with similar phenotypic characteristics on related hosts in Carex sect. Aulocystis in the same geographical area of southern Asia (Himalaya Mts) were described several decades later, Anthracoidea nepalensis on Carex nakaoana in Nepal (Kakishima & Ono 1988) and Anthracoidea haematostomae on Carex haematostoma in China (Guo 2006). These two smuts were found to be conspecific by Vánky & Piątek (in Vánky 2007b) and that treatment is followed in the monograph of Vánky (2012). This work aims to clarify the taxonomic status of Cintractia disciformis and ascertain whether it is distinct from or conspecific with Anthracoidea nepalensis (incl. A. haematostomae).

Materials and Methods

Sori and spore characteristics were studied using dried herbarium material deposited in H, IBAR and “H.U.V.”¹. The specimens were examined either by light microscopy (LM) and scanning electron microscopy (SEM) or only by light microscopy (LM).

For light microscopy (LM), small pieces of sori were mounted in lactic acid, heated to boiling point and cooled, and then examined under a Nikon Eclipse 80i light microscope. LM micrographs were taken with a Nikon DS-Fi1 camera. Fifty spores were measured from each collection, using NIS-Elements BR 3.0 imaging software. Spore size ranges were assigned to one of the three groups distinguished by Savile (1952): (1) small-sized spores — 13–21(–23) × 9–17(–20) µm; (2) medium-sized spores — 15–25(–27) × 10–21 µm; (3) large-sized spores — 18–33 × 13–28 µm. Unless otherwise stated, the spores were measured in plane view and measurements are adjusted to the nearest 0.5 µm.

For scanning electron microscopy (SEM), spores taken directly from dried herbarium samples were dusted onto carbon tabs and fixed to an aluminium stub with double-sided transparent tape. The stubs were sputter-coated with carbon using a Cressington sputter-coater and viewed under a Hitachi S-4700 scanning electron microscope, with a working distance of ca. 12 mm. SEM micrographs were taken in the Laboratory of Field Emission Scanning Electron Microscopy and Microanalysis at the Institute of Geological Sciences of Jagiellonian University (Kraków).

Results

Anthracoidea disciformis (Liro) M. Piątek, comb. nov.

MycoBank MB800481

(Fig. 1)

Fig. 1.

Anthracoidea disciformis (H s.n. — holotype). A. The holotype material. B–C. Enlarged sorus visible from both sides of inflorescence respectively. D–E. Spores in LM, median and superficial views respectively. F–I. Spores with prominent hyaline mucilaginous sheath on the flattened sides. Note small papillae on spore surface indicated by arrows on picture F. J–K. Spores in SEM. Note remnants of mucilaginous sheath on surface of spores illustrated on picture J and in central part of spore illustrated on picture K. L. Ornamentation of spore in SEM. Bars: A–C = 5 mm, D-J = 10 µm, K = 5 µm, L = 3 µm.

Basionym: Cintractia disciformis Liro, Myc. Fenn. fasc. 16, no. 110 (1939).

Synonyms: Cintractia disciformis Liro, Ann. Bot. Soc. zool.-bot. Fenn. “Vanamo” 6: 6 (1935); nom. inval. (Art. 36.1).

Anthracoidea disciformis (Liro) Zambett., Bull. Soc. mycol. France 94: 166 (1978); nom. inval. (Art. 33.4).

Anthracoidea nepalensis Kakish. & Y. Ono, in Watanabe & Malla, Crypt. Himal. 1: 128 (1988).

Anthracoidea haematostomae L. Guo, Fungal Diversity 21: 83 (2006).

Sorus in one ovary of the inflorescence, black, ovoid, presumably around the achene, about 4 × 2.5 mm diam, composed of agglutinated spores, powdery on the surface, partly hidden by the perigynium and scales. Spores small-sized, flattened, disc-shaped, chestnut-brown to reddish brown, regular in shape and size, in plane view globose, subglobose or broadly ellipsoidal, 16.5–18.5(–19.0) × (13.5–)14.0–18.0 µm [av. ± SD, 17.6 ± 0.6 × 15.7 ± 1.2 µm, n = 50], in side view broadly ellipsoidal (8.5–)10.0–12.0 µm (measurements without hyaline caps), usually enclosed by prominent mucilaginous sheath visible as hyaline caps on the flattened sides, up to 1.5 µm wide; wall even, 1.5–2.0 µm, darker than the rest of spore; surface finely papillate in LM, spore profile finely serrulate, surface sparsely papillate in SEM, papillae up to 0.3 µm high (from SEM micrographs), interspaces smooth.

Specimens examined: China: Yunnan Province: Deqen, elev. 2700 m, on Carex haematostoma, Sept. 1935, C.W. Wang 70101 (“H.U.V.” 20090, isotype of Anthracoidea haematostomae). — India: Darma, Nipchang, on Carex plectobasis (as “C. hirtella”), 31 Aug. 1884, J. F. Duthie (H s.n. — holotype of Cintractia disciformis). — Nepal: Bagmati Zone: Langtang, Kyangjin—Langshisa, elev. 3900 m, on Carex haematostoma (syn. C. nakaoana), 3 Sept. 1986, Y. Ono 86NE-223 (IBAR 0628 — isotype of Anthracoidea nepalensis); elev. 3800 m, on Carex haematostoma (syn. C. nakaoana), 3 Sept. 1986, Y. Ono 86NE-214 (IBAR 0619, paratype of Anthracoidea nepalensis); Kyangjin, elev. 3800 m, on Carex haematostoma (syn. C. nakaoana), 4 Sept. 1986, Y. Ono 86NE-234 (IBAR 0639 — paratype of Anthracoidea nepalensis).

Hosts and distribution: On members of Carex sect. Aulocystis: Carex digyna, C. haematostoma (syn. C. nakaoana), and C. plectobasis (syn. C. hirtella). Known from China, India, and Nepal.

Observations: While the host of Cintractia disciformis is uncertain according to the annotation by Ilkka Kukkonen on the holotype; re-identification of the specimen based on one inflorescence is difficult. However, the sedge definitely belongs to the section Aulocystis, and the length of perigynia (5.0–6.5 mm) indicates an affinity with Carex plectobasis (syn. C. hirtella) according to the available keys and descriptions in the Flora of Pakistan and Flora of China (eFloras, https://doi.org/www.efloras.org). Guo (1994) has also reported Anthracoidea nepalensis on this host (as Carex hirtella).

The host of Anthracoidea nepalensis was reported as Carex nakaoana, but this species is now considered synonymous with C. haematostoma (Chlebicki 2002). Yet another host of this smut is C. digyna listed in Chinese reports of A. nepalensis (Guo 1994, as “digyne”). The host of A. haematostomae is C. haematostoma. Vánky (2007b) included the European sedge C. sempervirens in the list of hosts of A. nepalensis; this was evidently a mistake, and the species was not cited as a host in his subsequent monograph (Vanky 2012). Carex sempervirens has to be excluded from the host range of A. disciformis.

Discussion

The internal structure of the sori is one of the main differentiating characteristics between Anthracoidea and Cintractia (Kukkonen 1963, Piepenbring 2000). Unfortunately this feature could not be examined in the holotype of Cintractia disciformis without destroying the specimen. However, the hyaline caps on the spores preclude a placement in Cintractia and support an affinity to Anthracoidea. Further, species of Cintractia are not known to occur on Carex, nor even members of the Cariceae (Piątek & Vánky 2007). The internal sorus structure of Anthracoidea nepalensis (Fig. 2), regarded here as a synonym, is typical of Anthracoidea species in that the spores are formed on the outer surface of the achene, and not within the U-shaped pockets embedded in the sterile stroma, a character of the genus Cintractia (Kukkonen 1963, Piepenbring 2000). This provides additional indirect evidence that Cintractia disciformis is a member of the genus Anthracoidea as indicated by Zambettakis (1978) and Vánky (2012).

Fig. 2.

Internal sorus structure of Anthracoidea nepalensis (IBAR 0619). A. Transverse section through the sorus. B. Enlarged area close to the achene surface. Abbreviations: n — rudimentary achene, e — dark layer of the remnants of the achene epidermis, h — layer of sporogeneous hyphae, s — layer of young hyaline spores, m — layer of gradually maturing dark spores. Bars: A = 20 µm, B = 10 µm.

The characteristics of the holotype of Cintractia disciformis are included in the species description presented above and shown in the illustrations (Fig. 1). The morphological details of specimens of Anthracoidea nepalensis I examined were: sori globose or ovoid surrounding the achenes, about 1.5–3.0 long and 1.5–2.5 mm wide, spores disc-shaped, chestnut-brown to reddish brown, globose, subglobose, rarely broadly ellipsoidal or somewhat subangulate, (15.0–)15.5–19.5(–20.5) × (12.5–)14.0–18.0(–19.0) µm, the flattened sides of spores rarely enclosed by a hyaline mucilaginous sheath, spore wall even, 1.0–1.5(–2.0) µm, spore surface finely papillate, spore profile finely serrulate. The SEM characteristics of spores of A. nepalensis (Kakishima & Ono 1988, Chlebicki 2002) agree well with those of Cintractia disciformis.

The morphology of Anthracoidea haematostomae was investigated by Vánky & Piątek (in Vánky 2007b) to establish the synonymy between this species and A. nepalensis, although only the morphology of A. nepalensis was presented in the published results. However, the key morphological features of the material of A. haematostomae studied are: spores dark reddish brown, 17.5–22 × 15–20 µm; spore wall even, 1.5–2.5 µm thick, with hyaline caps, spore surface finely papillate, spore profile finely wavy. The spore ornamentation observed in SEM (Guo 2006) also agrees well with that of Cintractia disciformis.

The morphology of Cintractia disciformis, Anthracoidea nepalensis and A. haematostomae is very similar, and the only differences concern the hyaline mucilaginous sheath. This sheath was less developed in the material of A. nepalensis, and the spores are somewhat larger and the spore wall slightly thicker in A. haematostomae compared to Cintractia disciformis. However, these minor differences lie within the normal variability of a single Anthracoidea species (Kukkonen 1963, Denchev 1991, Piątek & Mułenko 2010, Savchenko et al. in press). Consequently, these three species names are considered as synonymous and the oldest available name, Cintractia disciformis, is therefore taken up as a new combination, that proposed by Zambettakis (1978) being invalid.

The disc-shaped, papillate spores of Anthracoidea disciformis are distinctive and rarely observed in other Anthracoidea species that have verruculose or rarely smooth spores. This feature readily differentiates this smut from four other Anthracoidea species infecting members of Carex sect. Aulocystis which all have verruculose spores (viz. A. altera, A. misandrae, A. sempervirentis, and A. stenocarpae). In the entire genus, only a few other Anthracoidea species have disc-shaped and papillate spores, for example A. bistaminatae (Guo 2006), A. lindebergiae (Vánky 1994), A. mulenkoi (Piątek 2006), A. pygmaea (Guo 2002), A. royleanae (Guo 2006), A. setschwanensis (Guo 2007), A. smithii (Vánky 2007a), and A. xizangensis (Guo 2005), all of which infect Kobresia. Interestingly, most of these Anthracoidea species occur in eastern and southern Asia. An exception is A. lindebergiae, which is widely distributed in arctic and alpine ecosystems of the Northern Hemisphere. Whether these Anthracoidea species are closely related and have evolved from a common ancestor is unclear and open to future studies.

This study demonstrates that a critical evaluation of historical names could prevent an unnecessary proliferation of names proposed for the same organism. Such taxonomical expertise appears even more urgent in the light of molecular initiatives, especially DNA Barcoding (Seifert 2008, Begerow et al. 2010, Schoch et al. 2012). In orderto be most effective the molecular studies should be accompanied by a critical reassessment of as many historical names of fungal species as possible that can be linked to freshly collected specimens for use in molecular analyses (Lücking 2008, Hyde et al. 2010).