Chaetosphaeronema hispidulum (Corda) Moesz, Bot. Közl. 14: 152 (1915)
= Chaetosphaeronema achilleae S.K. Huang & K.D. Hyde, in Hyde et al., Fungal Divers. 80: 1–270 (2016)
= Ophiobolus cirsii (P. Karst.) Sacc., Syll. fung. 2: 341 (1883)
Saprobic on dead stem of Achillea nobilis, Onobrychis sp., Medicago sp. Sexual morph: Ascomata dark brown to black, solitary to gregarious or confluent, visible as spots on the host surface, immersed to semi-immersed, globose to subglobose, unilocular, glabrous, thick-walled, papillate, ostiolate. Ostiole single, cylindrical, centrally located. Peridium composed of thick-walled, dark brown to pale brown or hyaline cells of textura angularis. Hamathecium consisting of asci and pseudoparaphyses. Pseudoparaphyses hyaline, broad cellular, septate, constricted at septa, branched, smooth-walled. Asci 8-spored, bitunicate, with indistinct ocular chamber, cylindrical to cylindric-clavate, with rounded apex and short pedicel. Ascospores greenish yellow, overlapping or lying parallel or spiral, without sheath or appendages, septate, inflated at 10th cell, the inflation more pronounced near the 9th septum, apical part bent or curved (Ariyawansa et al. 2014). Asexual morph: Conidiomata 180–260 µm diam., 150–390 µm high, dark brown to black, pycnidial, solitary to gregarious, deeply immersed with only the dark brown, rostrate ostiole visible in surface view, globose to subglobose, unilocular, setose, thick-walled, ostiolate. Ostiole 140–200 × 70–110 µm, single, cylindrical to obconical, straight or curved, covered by dark brown to brown setae. Conidiomatal setae 70–130 × 4–6 µm, restricted to the beak, dark brown and blunt at base, becoming paler and attenuated towards top, septate, unbranched, smooth-walled. Conidiomatal wall 15–70 µm wide, composed of relatively thick-walled dark brown to pale brown cells of textura angularis in the upper part and ostiolar region, with thick-walled, pale brown to hyaline cells of textura angularis gradually merging with textura prismatica in the basal and lateral part. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 4–10 × 2–4 µm, hyaline, enteroblastic, annelidic, cylindrical to lageniform, determinate, smooth-walled, with periclinal thickenings at collarette zone, or percurrently proliferating 1–2 times. Conidia 7–12 × 1.6–2.2 µm (x = 10 × 1.9 µm; n = 50), hyaline, cylindrical, rounded at apex, blunt and truncate at base, straight or slightly curved, 1-septate, without constrictions at the septum, often guttulate, smooth-walled.
Culture characters: Strain MFLUCC 17–2503, colonies on PDA, reaching 30–40 mm diam. after 30 d at 20–25°C, producing globules, pale brown in the middle zone, with dense, flattened, filamentous, cottony, aerial hyphae, brown in the margin area, margin circular, with sparse, filiform aerial hyphae, reverse dark brown; strain MFLUCC 17–1317, colonies on PDA, reaching 50–60 mm diam. after 21 d at 20–25°C, with pale brown to brown, dense, flattened, filamentous, fluffy, aerial hyphae in the middle zone, white, sparse, circular, entire; aerial hyphae in the margin region, reverse pale brown to brown.
Material examined: Russia, Rostov Region, Oktyabrsky District, southern outskirts of Persianovky settlement, Khoruli gully (rus. balka Khoruli), on dead stems of Achillea nobilis (Asteraceae), 28 April 2015, T.S. Bulgakov, T218 (MFLU 15-1922); ibid., Italy, Province of Forlì-Cesena, Premilcuore, Passo della Braccina, on dead aerial stems of Onobrychis viciifolia (Fabaceae), 31 July 2016, Erio Camporesi, IT3050 (MFLU 16-2275), living culture MFLUCC 17-2503, (KUN, HKAS 101659); ibid., Province of Arezzo, near Poppi, on dead aerial stems of Medicago sp. (Fabaceae), 13 June 2016, Erio Camporesi, IT2998 (MFLU 16-1965), living culture MFLUCC 17-1317 = ICMP 21551= KUMCC 16-0103, (KUN, HKAS 97468).
Notes: Chaetosphaeronema achilleae was introduced as a new taxon based on its smaller, glabrous conidiomata with textura angularis cells and lack of conidiomatal setae (Hyde et al. 2016). After re-examining the type specimen, we found that it has setose conidiomata with textura angularis to textura prismatica cells. The conidiogenous cells are percurrently proliferating 1–2 times. The LSU and ITS sequences of C. achilleae differ from C. hispidulum in only 2 base pairs. Thus, C. achilleae is considered as conspecific with C. hispidulum. Two new collections were distinguished from C. hispidulum by smaller and glabrous conidiomata, but molecular data proved they are the same species. Thus, setose pycnidia and dimension of conidiomata are not stable characters to delineate the species in Chaetosphaeronema. A revised description and photos are provided for C. hispidulum.
Chaetosphaeronema hispidulum (MFLU 15–1922) a, b Herbarium package and specimen. c, d Appearance of dark brown to black coniodiomata on the host, note d black ostiole in surface view. e, f, g Vertical sections of conidiomata. h Conidiomatal setae. i Ostiole. j Vertical section of peridium. k Ostiole with periphyses. l–r Conidiogenous cells and developing conidia (arrows show 2 annellides). s–x Conidia. Scale bars c–d = 200 µm, e–g = 100 µm, h–i, k = 20 µm, j = 50 µm, l–x = 5 µm.