Thyridium Nitschke, Pyrenomyc. Germ. 1: 110 (1867).

MycoBank number: MB 5465; Index Fungorum number: IF 5465; Faceoffungi number: FoF 02137;

Melanospora subgen. Bivonella Sacc., Syll. fung. (Abellini) 2: 464 (1883).

Bivonella (Sacc.) Sacc., Syll. fung. (Abellini) 9: 989 (1891).

Pleurocytospora Petr., Annls mycol. 21: 256 (1923).

Sinosphaeria J.Z. Yue & O.E. Erikss., Syst. Ascom. 6: 231 (1987).

Phialemoniopsis Perdomo, Dania García, Gené, Cano & Guarro, Mycologia 105: 408 (2013).

Type species. Thyridium vestitum (Fr.) Fuckel, Jb. nassau.Ver. Naturk. 23–24: 195 (1870) [1869–70].

Sexual morph. Stromata scattered to grouped, subepidermal to erumpent, yellowish to dark brown, red in KOH or not changing. Ascomata perithecial, subglobose to ampulliform, single to grouped, immersed in stromata to erumpent through host surface. Ascomatal wall composed of several layers of polygonal, dark brown cells. Ostiolar neck cylindrical, short or long, separated or convergent in upper stromata, periphysate. Paraphyses numerous, septate, unbranched, cylindrical, hyaline. Asci uni- tunicate, cylindrical, broadly rounded at the apex, with a pronounced non-amyloid apical annulus, pedicellate. Ascospores obovoid or ellipsoid, smooth, pale brown to brown, with several transverse and 0–3 longitudinal or oblique septa.

Asexual morph. Coelomycetous and/or hyphomycetous morphs formed. Coelomycetous asexual morph: Conidiomata pycnidial, single to grouped, superficial or immersed in stromata, globose to subglobose, composed of polygonal to prismatic cells, often becoming cup-shaped when mature, surrounded by setose hyphae. Conidiomatal wall composed of several layers of polygonal, dark brown cells. Ostiolar neck cylindrical, central, periphysate. Setose hyphae erect, usually unbranched, septate, cylindrical, with slightly pointed or blunt tips, hyaline to pale brown, smooth-walled. Conidiophores hyaline, thin-walled, simple or irregularly branched, with branches bearing a small group of phialides terminally. Phialides swollen at the base, tapering at the tip, hyaline. Conidia obovoid to oblong, with a slightly apiculate base, hyaline, smooth- walled, in slimy masses. Hyphomycetous synasexual morph: Colonies effuse or sporodochial. Conidiophores micronematous, mononematous, hyaline, thin-walled, simple or irregularly branched, with branches bearing a small group of phialides terminally. Phialides swollen at the base, tapering at the tip, hyaline. Adelophialides absent or rarely present. Conidia ellipsoidal to allantoid, with a slightly apiculate base, hyaline, smooth-walled, in slimy head. Chlamydospores absent or rarely present, hyaline to pale brown, thick- and rough-walled.

Notes. The newly obtained Thyridium collections formed synasexual morphs, coelomycetous and hyphomycetous, in culture that were similar to those of Phialemoniopsis, having coelomycetous and/or hyphomycetous conidial states in culture (Perdomo et al. 2013). In this study, Phialemoniopsis is treated as a synonym of Thyridium because of their morphological similarities in asexual morphs and phylogenetic relatedness. The genus Pleurocytospora has been proposed as a synonym of Thyridium by culture studies (Leuchtmann and Müller 1986). We agree that the morphological features of Pleurocytospora, such as phialidic conidiogenous cells and hyaline, ellipsoidal conidia formed from both coelomycetous and hyphomycetous states (Leuchtmann and Müller 1986), are almost identical to those of the generic concept of Thyridium emended here.

We accept both Bivonella and Sinosphaeria as synonyms of Thyridium, as proposed in previous studies (Eriksson and Yue 1989; Checa et al. 2013). Sinosphaeria (typified by S. bambusicola = Thyridium chrysomallum; Yue and Eriksson 1987) was established as a new genus without knowing the existence of Bivonella (typified by B. lycopersici; Saccardo 1891). Both genera are characterised by yellowish stromata. The validity of these genera being synonymised under Thyridium is confirmed by the presence of T. flavostromatum, which has yellowish stromata, in the strongly supported Thyridium clade (Fig. 1).

Figure 1. Maximum-likelihood tree of Sordariomycetes based on combined LSU, rpb2 and tef1 se- quence. ML bootstrap proportion (BP) greater than 70% and Bayesian posterior probabilities (PP) above 0.95 are presented at the nodes as ML BP/Bayesian PP and a node not present in the Bayesian analysis is shown with ‘x’. A hyphen (‘-’) indicates values lower than 70% BP or 0.95 PP. Ex-holotype, isotype, paratype and epitype strains are shown in bold and the newly obtained sequences are shown in red. Strains previously described as Phialemoniopsis species are marked with a blue circle. The scale bar represents nucleotide substitutions per site.

Species

  • Thyridium vestitum