Fungalpedia – Note 3318, Mixiomycetes
Mixiomycetes R. Bauer, Begerow, J.P. Samp., M. Weiss & Oberw., Mycol. Progr. 5(1): 47 (2006).
Citation when using this data: Wijayawardene NN et al. 2024 – Fungalpedia.
Index Fungorum, Faceoffungi, MycoBank, GenBank, Fig 1.
Classification: Pucciniomycotina, Basidiomycota, Dikarya, Fungi.
Asexual morph: Sporogenous cells developing on the surface of the host epidermal cells, the host cell walls are thickened at the contact area with the hyphal cells; sporogenous cells fusiform, oblong, ellipsoid, pyriform, or bacilliform, without septa. Hyphal cells are multinucleate, electron transparent, and nonfibrillate; numerous spores are produced exogenously, enteroblastically and simultaneously from the sporogenous cells. The spores are hyaline and ellipsoidal. At the surface of the sporogenous cell, after the release of the spores, numerous tiny denticles were observed using light microscopy. The denticles are cuneiform, ca. 0.5 μm in diameter at the tip and were slightly sunken at the center Sexual morph: Unknown (Nishida et al. 1995; Bauer et al. 2006).
Life modes and Distribution: Parasitic on ferns Osmunda regalis, O. japonica and Osmundastrum cinnamomeum (Nishida et al. 1995; Sugiyama et al. 2018).
Notes: The class Mixiomycetes was introduced by Bauer et al. (2006). According to Wijayawardene et al. (2020a) and He et al. (2024), Mixiomycetes comprises one order, Mixiales, which include a single family Mixiaceae (type: Mixia).
Mixia osmundae is the sole known species in the Mixiomycetes. For more than 80 years, it was identified as an ascomycete called Taphrina osmundae, partly because the sporogenous cells of Mixia have some superficial resemblance to the asci produced by certain Ascomycota (Aime et al. 2014). However, subsequent revaluation based on examination of cell wall ultrastructure and the observation of enteroblastic budding led to its reclassification as a Basidiomycetes (Boekhout et al. 2011).
According to Wang et al. (2015a), Mixiomycetes is placed phylogenetically as a sister of Spiculogloeales which is an order of Agaricostilbomycetes. Other analyses by Wang et al. (2015a), Hibbett et al. (2007), and Aime et al. (2014) found various placements for Mixiomycetes, where it was not sister to Spiculogloeales. The identification of new taxa within the monotypic class Mixiomycetes, as well as the place of additional taxa and sequences from subphylum Pucciniomycotina, will be necessary to complete the phylogenetic placement of genus Mixia.
Type order: Mixiales R. Bauer, Begerow, J.P. Samp., M. Weiss & Oberw., Mycol. Progr. 5(1): 47 (2006).
Type family: Mixiaceae C.L. Kramer, Stud. Mycol. 30: 159 (1987).
Type genus: Mixia C.L. Kramer, Mycologia 50(6): 924 (1959) [1958].
Type species: Mixia osmundae (Nishida) C.L. Kramer, Mycologia 50(6): 924 (1959) [1958].
Other accepted species: Species Fungorum – search Mixiomycetes.
Figure 1 – Mixia osmundae on Osmunda japonica. (a–c) Ultrathin sections of showing the sporogenous cell from which spores are enteroblastically produced (redrawn from Nishida et al. 1995).
References
Entry by
Nalin N. Wijayawardene, Center for Yunnan Plateau Biological Resources Protection and Utilization, College of Biological Resource and Food Engineering, Qujing Normal University, Qujing, Yunnan 655011, P.R. China, Tropical Microbiology Research Foundation, 96/N/10, Meemanagoda Road, 10230 Pannipitiya, Sri Lanka, Department of Bioprocess Technology, Faculty of Technology, Rajarata University, Sri Lanka
Published online 2 October 2026