Didymellaceae Gruyter, Aveskamp & Verkley, Mycol. Res. 113(4): 516 (2009).
= Microsphaeropsidaceae Q. Chen et al.
MycoBank number: MB 508292; Index Fungorum number: IF 508292; Facesoffungi number: FoF 08216, >300 species.
Endophytic, pathogenic and saprobic on a wide range of hosts worldwide. Sexual morph: Pseudothecia immersed, rarely superficial, separate or gregarious, globose to flattened, ostiolate, with 2–5(–8) layers of pseudoparenchymatal cells. Ostiole: Asci arising from a broad hymenium among pseudoparaphyses. Hamathecium of mostly cellular pseudoparaphyses. Asci 8-spored, bitunicate, cylindrical to clavate or saccate. Ascospores mostly hyaline, or brownish, 1-septate spores (didymospores) or multi-septate dictyospores. Asexual morph: Coelomycetous. Conidiomata pycnidial, immersed, or semi immersed, sometimes becoming erumpent, uni-locular, pale to medium brown, globose, thin or thick-walled, peridium with cells of textura angularis. Ostiole central, circular, papillate or not. Conidiophores mostly absent, and then either filiform, septate, and branched, or short, irregularly branched and ramified respectively. Conidiogenous cells enteroblastic, phialidic, doliiform to lageniform, ampulliform or cylindrical, hyaline, thin-walled, smooth-walled. Conidia ellipsoid, cylindrical, fusiform, pyriform or globose, hyaline or pigmented, septate or aseptate, thin-walled, guttulate.
Type – Didymella Sacc.
Notes – Species belonging to Didymellaceae are cosmopolitan. They have a wide range of hosts and many are pathogens (Chen et al. 2015). They also include endophytes, fungicolous and lichenicolous taxa. Didymellaceae was introduced by de Gruyter et al. (2009). This family is the largest family in the Pleosporales (Ascomycota, Pezizomycotina, Dothideomycetes). In the beginning, Didymellaceae consisted of Ascochyta, Didymella and Phoma (Aveskamp et al. 2010). Aveskamp et al. (2010) redefined Epicoccum, Peyronellaea Gold. ex Togliani and Stagonosporopsis and introduced Boeremia. After several years of species conflicts, Chen et al. (2015) accepted 17 well supported monophyletic clades in Didymellaceae as individual genera. In the same study, Microsphaeropsis was introduced into new family Microsphaeropsidaceae as these species are distinct from the members of Didymellaceae and phylogenetically this genus is basal to the Didymellaceae (Chen et al., 2015). A phylogenetic analysis conducted by Wanasinghe et al. (2018b) showed that this genus clusters within Didymellaceae and closely related to Macroventuria. Similar results are observed in this study (Fig. 76). In Didymellaceae, sexual morphs are rare compared to the asexual morph. Therefore, it is difficult to compare sexual morphs and exclude this genus under Didymellaceae. In asexual morphs, most of the characters (Chen et al. 2017) are shared and similar to other genera in family Didymellaceae. Hence in this study, we accept Microsphaeropsis in Didymellaceae.
After Chen et al. (2015), several other genera were added to this family. These include Briansuttonomyces (Crous & Groenewald 2016), Neomicrosphaeropsis (Thambugala et al. 2017a), Didymellocamarosporium (Wijayawardene et al. 2016a), Heracleicola and Neodidymella (Ariyawansa et al. 2015a). Didymellocamarosporium was introduced by Wijayawardene et al. (2016a) as a monotypic genus. Furthermore, Chen et al. (2017) conducted a phylogenetic analysis using DNA sequence data (LSU region) of the type species of this genus and showed that this species is embedded within Neomicrosphaeropsis. Similar results are observed in the phylogenetic analysis conducted in this study (Fig. 76). Therefore, we synonymize Didymellocamarosporium under Neomicrosphaeropsis. Ariyawansa et al. (2015a) introduced Neodidymella. Until now, sequence data for Neodidymella were not available in the NCBI database. Therefore, this genus was ignored by previous studies. However, we accept this genus in Didymellaceae with molecular data (Fig. 76). In Wijayawardene et al. (2017a), the following genera have been accepted under Didymellaceae; Chaetasbolisia, Endocoryneum, Endophoma, Mixtura, Monascostrom, Peyronellaea, Phaeomycocentrospora, Platychora and Pseudohendersonia. Phaeomycocentrospora is accepted under Dothidotthiaceae by MarinFelix et al. (2017), Wijayawardene et al. (2018), and Crous et al. (2019a). In addition to that, Endocoryneum is referred to genera incertae sedis in Pezizomycotina (Ascomycota). Phaeomycocentrospora and Endocoryneum are not accepted in Didymellaceae.
Endophoma was introduced by Tsuneda et al. (2011) to Didymellaceae. In this study, they have used ITS, LSU, and tub2 regions in phylogenetic analysis in which Endophoma clusters within the Phoma clade. In addition to that, the authors have mentioned Endophoma elongata (the type species) has close phylogenetic relationships to Phoma eupyrena while mentioning that pairwise similarity across above three gene regions are 100 %. Even though it has not mentioned in the recent studies that this genus should be synonymized to Phoma. Wijayawardene et al. (2016a) introduced Pseudohendersonia galiorum to Pseudohendersonia. However, the authors introduced this with only LSU sequence data and Chen et al. (2017) proposed that this is morphologically similar to genera like Ascochyta, Boeremia, Stagonosporopsis and Neomicrosphaeropsis. Therefore, recent studies did not accept this genus under Didymellaceae (Marin-Felix et al. 2017). Before adding this genus under Didymellaceae further studies are necessary. Species of Peyronellaea has been synonymized under Didymella and Phoma by Marin-Felix et al. (2017).
The remaining genera Chaetasbolisia, Mixtura, Monascostrom, and Platychora are ill studied genera in family Didymellaceae. Among them Mixtura and Monascostroma were classified under Phaeosphaeriaceae. Phookamsak et al. (2014c) studied the type material of Mixtura saginata and tentatively placed it in Didymellaceae. Most of the morphological characters of Monascostrom support that it should be a member in Didymellaceae and Schoch et al. (2009a) confirmed its taxonomic placement in Didymellaceae. Therefore, following morphological evidence from Schoch et al. (2009a), Hyde et al. (2013), Phookamsak et al. (2014c), Wijayawardene et al. (2018) and from this study, we accept these four genera under Didymellaceae but we reckon further studies are still necessary. In addition, two new genera were introduced, Anthodidymella (Phukhamsakda et al. 2020) and Vandijckomycella (Hou et al. 2020). Based on the above discussion we accept 35 genera in Didymellaceae.