Fungalpedia – Note 1349, Asteromella
Asteromella. Pass. & Thüm.
Index Fungorum, Facesoffungi, MycoBank, GenBank, Fig 1
Classification: Incertae sedis, Incertae sedis, Incertae sedis, Incertae sedis, Pezizomycotina, Ascomycota, Fungi
Asteromella species are epifoliar fungi which form blackened circular areas on leaves. The mycelium is immersed, hyaline or pale brown, branched and septate. The sexual morph of this species have not been reported. The asexual morph is characterised by immersed conidiomata, which are dark brown, globose to subglobose, unilocular and occur singly or in groups. The ostiole is papillate and circular, located in the center. The conidiomatal wall is composed of brown, thick-walled cells, primarily textura angularis. Conidiophores are formed from the inner cells of the conidiomata wall, which are hyaline, cylindrical, 1-3 septate and branched at base. Conidiogenous cells are hyaline, enteroblastic, phialidic, cylindrical or conical to globose or subglobose, primarily integrated and rarely discrete. Conidia are hyaline, smooth-walled, cylindrical to oval, aseptate and eguttulate (Sutton 1980, Vanev and van der Aa 1998, Ruszkiewicz-Michalska 2016, Li et al. 2020).
Notes: Asteromella was introduced by Passerini and Thümen (1880) based on Asteromella ovata as the type species. Astrospora species are generally considered to be the microconidial or spermogonial state of Mycosphaerella species (Vanev and Van Der Aa 1998, Crous et al. 2009). Ruszkiewicz-Michalska (2016) provides a detailed account of the history and generic concepts of the genus. Pem et al. (2019) re-examined the holotype specimen of Asteromella ovata from the fungal herbarium collections of Swedish Museum of Natural History and compared morphological characters with the original specimen. They retain the genus to Dothideomycetes genera incertae sedis due to its “Phoma” like conidia and limited morphological characteristics. Currently, there are 226 species names of Asteromella listed in Species Fungorum (May, 2024). However, molecular data are rare in Asteromella, only ten sequences are available in GenBank (May, 2024). Therefore more collections are necessary to provide molecular data as molecular studies are necessary to clarify the generic concept of Asteromella. The updated taxonomic treatment of this genus is genera incertae sedis, in Dothideomycetes (Wijayawardene et al. 2022).
Type species: Asteromella ovata Thüm., Mycoth. Univ., cent. 17: no. 1689 (1880).
Figure 1 – Asteromella ovata (redrawn from Sutton 1980) a Vertical section of conidioma. b Conidia. c Conidiophores, conidiogenous cells and developing conidia. Scale bars a = 50 μm, c = 10 μm. (Originally published in Li et al. (2020) and republished with authority)
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