Fungalpedia – Note 560, Exoteliospora
Exoteliospora R. Bauer, Oberw. & Vánky
Citation when using this data: Zhang et al. 2025 (in prep.) – Fungalpedia, Basidiomycota.
Index Fungorum, Facesoffungi, MycoBank, GenBank, Fig. 1
Classification: Melanotaeniaceae, Ustilaginales, Ustilaginomycetidae, Ustilaginomycetes, Ustilaginomycotina, Basidiomycota, Fungi
The genus Exoteliospora was introduced in Melanotaeniaceae based on evidence of sporulation, septal pore apparatus, and host-parasite interaction between E. osmundae (Bas. Ustilago osmundae) and its host of the royal fern Osmunda regalis, using light and electron microscopy (Bauer et al. 1999a). Exoteliospora comprises a single species, E. osmundae, which was originally known as a smut fungus infecting ferns (Peck 1881), but was reclassified as a hyphomycete (Clinton 1904). Subsequently, E. osmundae was considered a basidiomycete based on the ultrastructure of the hyphal wall and septal pore (Vánky 1996). Currently, E. osmundae is recognized as a smut fungus due to the understanding that smut fungi evolved in different fungal groups (Bauer et al. 1997, 1999a). This conclusion is significant as it provides key evidence for host jumping (the host range of smuts from angiosperms to ferns) (Bauer et al. 1997). It is noteworthy that E. osmundae has been found on several collections of Osmunda spp. in North America, suggesting that the host range of Exoteliospora is likely restricted to the fern genus Osmunda.
The monotypic genus exhibits a unique morphology, with thick-walled and thin-walled hyphae forming coralloid haustoria with numerous lobes in epidermal cells, hyphae absent, lacking in intercellular spaces, globose to subglobose teliospores produced in basipetal chains, and septal pores with non-swollen lips and membrane caps, composed of a simple pore with two caps (Peck 1881; Vánky 1996; Bauer et al. 1999a). The characteristic external sporulation and absence of intercellular hyphae are prominent features of Exoteliospora (Bauer et al. 1999a) in Melanotaeniaceae of Ustilaginomycetes, Basidiomycota (Hyde et al. 2024c).
Type species: Exoteliospora osmundae (Peck) R. Bauer, Oberw. & Vánky.
≡ Ustilago osmundae Peck.
≡ Mycosyrinx osmundae (Peck) Peck.
Other accepted species: Species Fungorum – search Exoteliospora.
Figure 1 – Exoteliospora osmundae. a Coralloid haustoria in epidermal cells from a freehand section and the mode of teliosporogenesis. b Section through a hypha showing the fibrillate wall. c Teliospores (LM). d Teliospores (SEM). Redrawn from Bauer et al. (1999a).
References
Bauer R, Oberwinkler F, Vánky K 1999a – Ustilaginomycetes on Osmunda. Mycologia 91:669–675.
Clinton GP 1904 – North American Ustilagineae. Boston Society of Natural History.
Hyde KD, et al. 2024c – The 2024 outline of fungi and fungus-like taxa. Mycosphere (in press).
Peck CH 1881 – New species of fungi. Bot Gaz 6:274–279.
Vánky K 1996 – Mycosyrinx and other pair-spored Ustilaginales. Mycoscience.
Entry by
Jing-Yi Zhang, School of Food and Pharmaceutical Engineering, Guizhou Institute of Technology, Guiyang, 550025, People’s Republic of China, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai, 57100, Thailand, School of Science, Mae Fah Luang University, Chiang Rai, 57100, Thailand, Guizhou Key Laboratory of Agricultural Microbiology, Guizhou Academy of Agricultural Sciences, Guiyang, 550009, People’s Republic of China.
Published online 11 June 2025