Fungalpedia – Note 2249, Actidium
Actidium Fr.
Citation when using this data: Hongsanan S et al. 2020 – Fungalpedia, Ascomycota.
Index Fungorum, Facesoffungi, MycoBank, GenBank.
Classification: Mytilinidiaceae, Mytilinidiales, Pleosporomycetidae, Dothideomycetes, Pezizomycotina, Ascomycota, Fungi
This genus was established by Fries (1823) to accommodate A. hysterioides, a stellate mytilinidioid fungus found on Pinus and Picea in Europe, with two-celled, symmetric ascospores, light olive to reddish brown, later noted to be faintly longitudinally striate (Barr 1990a). Fries (1823) noted its similarity with Glonium. Zogg (1962) and Barr (1990b) recognised four species, A. hysterioides, A. baccarinii, both from Europe, A. pulchra, from China, and A. nitidum. Due to similarities in ascospore morphology, Actidium may have affinities with other didymospored hysteriaceous genera (e.g. Actidiographium, Glonium and Psiloglonium), although molecular data are lacking.
Type species: Actidium hysterioides Fr., Observ. mycol. (Havniae) 2: 353 (1818).
Other accepted species: Species Fungorum – search Actidium.
References
Barr ME. 1990a – Melanommatales (Loculoascomycetes). North American Flora 13(II), 1–129.
Fries EM. 1823 – Systema Mycologicum, sistens fungorum ordines, genera et species hucusque cognitas, II, pars II, 276–620.
Entry by
Sinang Hongsanan, Guangdong Provincial Key Laboratory for Plant Epigenetics, Shenzhen Key Laboratory of Microbial Genetic Engineering, College of Life Science and Oceanography, Shenzhen University, Shenzhen 518060, People’s Republic of China, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai 57100, Thailand, Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50002, Thailand
Published online 3 April 2026