Thyridiaceae J.Z. Yue & O.E. Erikss., Syst. Ascom. 6(2): 233 (1987)

Index Fungorum number: IF82030; 35 species.

Hemibiotrophic or saprobic on woody substrates. Sexual morph: Ascomata stromatic. Stromatal tissue immersed, becoming erumpent to superficial, soft textured, reddish brown to brightly pigmented. Ascomata immersed in stromata, globose, ostiolate. Ostioles periphysate, with short or long papilla or necks, sometimes convergent necks merging into one ostiole. Peridium composed of compressed rows of cells, externally brown, internally hyaline. Paraphyses filamentous, septate. Asci 8-spored, unitunicate, oblong cylindric, apical ring J-. Ascospores uniseriate, shades of brown, ellipsoid or biconoid, symmetric, 1-septate or muriform. Asexual morph: Coelomycetous or hyphomycetous, often developing on the edge of sexual morph stroma. Conidiomata immersed in stromata, irregular, multilocular and folded inside. Conidiogenous cells emerging from the interior of the cavity, bearing one or more conidiogenous cells. Conidiogenous cells enteroblastic, phialidic, hyaline. Conidia ellipsoidal, aseptate, small, hyaline. Holoblastic sympodial conidia also produced from hyphae. Sometimes ascospores produce primary conidia (adapted from Barr 1990b, Leuchtmann & Müller 1986, Maharachchikumbura et al. 2016).

Type genusThyridium Nitschke

Notes – In a phylogenetic and molecular clock analyses, Thyridiaceae showed a close relationship to Annulatascales and Myrmecridiales (Hyde et al. 2017a, Hongsanan et al. 2017, Senanayake et al. 2017a). However, only a single strain of the type genus has sequence data (Thyridium vestitum strain AFTOL-ID 172), and the ordinal placement remains uncertain in Diaporthomycetidae (Maharachchikumbura et al. 2015b, 2016b, Hongsanan et al. 2017). Maharachchikumbura et al. (2015, 2016) and Wijayawardene et al. (2018a) accepted three genera in Thyridiaceae (Mattirolia, Pleurocytospora, and Thyridium). No sequence data are available for Pleurocytospora species. Mattirolia has been synonymised under Thyronectria (Nectriaceae) by Jaklitsch & Voglmayr (2014) based on an ex epitype sequence of the generic type of Mattirolia, M. roseovirens. Here we follow the treatment of Jaklitsch & Voglmayr (2014).

Ecological and economic significance of Thyridiaceae

Species of Thyridium are saprobic on woody substrates (Checa et al. 2013, Zhou & Hyde 2002). Pleurocytospora species are saprobic or hemibiotrophic in woody substrates (Barr 1990b, Zhu et al. 2005) and therefore, involved in nutrient recycling. Pleurocytospora taxi was recorded from Taxus cuspidata, while P. lycii was isolated from Arabidopsis thaliana as an endophyte (Sun et al. 2003, Wang et al. 2015a, Junker et al. 2012) and there are no records of pathogenic species in Thyridiaceae.

Figure – Phylogram generated from maximum likelihood analysis based on combined LSU, SSU, ITS and rpb2 sequence data of Diaporthomycetidae. One hundred and ninety-three strains are included in the combined analyses which comprised 3545 characters (859 characters for LSU, 972 characters for SSU, 659 characters for ITS) after alignment. Single gene analyses were carried out and the topology of each tree had clade stability. Tree topology of the maximum likelihood analysis is similar to the Bayesian analysis. The best RaxML tree with a final likelihood value of – 68207.368884 is presented. Estimated base frequencies were as follows: A = 0.248206, C = 0.241993, G = 0.285500, T = 0.224301; substitution rates AC = 1.369088, AG = 2.887040, AT = 1.413053, CG = 1.152137, CT = 6.303994, GT = 1.000000; gamma distribution shape parameter a = 0.315782. Bootstrap support values for ML greater than 75% and Bayesian posterior probabilities greater than 0.95 are given near the nodes. The tree is rooted with Diatrype disciformis (AFTOL-ID 927). Ex-type strains are in bold. The newly generated sequences are indicated in blue.