Fungalpedia – Note 3292, Alloascoideomycetes
Alloascoideomycetes M. Groenew., Hittinger, Opulente & A. Rokas Stud. Mycol. 105: 7 (2023).
Citation when using this data: Wijayawardene NN et al. 2024 – Fungalpedia.
Index Fungorum, Faceoffungi, MycoBank, GenBank, Fig 1a,b-d.
Classification: Saccharomycotina, Ascomycota, Dikarya, Fungi.
Notes: The class Alloascoideomycetes in subphylum Saccharomycotina was introduced by Groenewald et al. (2023), who, based on the analysis of genomic data, proposed the distribution of the yeasts assigned to Saccharomycotina among seven classes. They provided a diagnosis of Alloascoideomycetes with class-specific orthologous groups of proteins (OGs). For more details, see the entry Saccharomycetes. Analysis of the two yeast DNA barcodes, LSU rDNA, SSU rDNA, and the gene sequence for the D1/D2 domain of the LSU rDNA (Kurtzman and Robnett 1998) indicated that two Ascoidea species, Ascoidea africana and Ascoidea hylecoeti are not closely related to Ascoidea rubescens. Kurtzman and Robnett (2013a) clearly divided Ascoidea species into two genera, Ascoidea and Alloascoidea, where the latter was included as the sole genus in the family Alloascoideaceae. Alloascoidea was found to be homothallic and produces clusters of more than eight ascospores in an ascus (Kurtzman and Robnett 2013a). Groenewald et al. (2023) is the latest study that provides a comprehensive background on the taxonomy of the higher-level classification of Alloascoideomycetes. Although only two species of Alloascoidea are presented by the class, Groenewald et al. (2023) propose the separation of Alloascoidea from its closest relative, Sporopachydermia, due to their long branches into two sister classes.
According to Groenewald et al. (2023), currently, the class comprises one order Alloascoideales, one family Alloascoideaceae, and one genus Alloascoidea.
Type order: Alloascoideales M. Groenew., Hittinger, Opulente & A. Rokas. Stud. Mycol. 105: 7 (2023).
Type family: Alloascoideaceae Kurtzman & Robnett, FEMS Yeast Res. 13: 429 (2013).
Type genus: Alloascoidea Kurtzman & Robnett, FEMS Yeast Res. 13: 426 (2013).
Type species: Alloascoidea hylecoeti (L.R. Batra & Francke-Grosm.) Kurtzman & Robnett, FEMS Yeast Res. 13: 427 (2013).
Other accepted species: Species Fungorum – search Alloascoideomycetes
Figure 1 – Microscopic features of taxa in Saccharomycotina. a Septate non-sporulating hyphae and pseudohyphae of Alloascoidea hylecoeti (Alloascoideaceae, Alloascoideales, Alloascoideomycetes). b-d Alloascoidea africana (Alloascoideaceae, Alloascoideales, Alloascoideomycetes) asci with ascospores and released ascospores (indicated with arrows). e,f Dipodascus albidus (Dipodascaceae, Dipodascales, Dipodascomycetes). e. Ascospores within hyphae and released ascospores. f Hyphae, arthroconidia and ascospores (indicated by arrow). g Lipomyces starkeyi (Lipomycetaceae, Lipomycetales, Lipomycetes) conjugation between a cell and its bud, ascus with ellipsoidal ascospores (indicated by arrows). h-j Pichia membranifaciens (Pichiaceae, Pichiales, Pichiomycetes) budding cells and asci with hat-shaped ascospores (indicated by arrows). k Pachysolen tannophilus (Pachysolenaceae, Alaninales, Pichiomycetes) budding cells, ascus with ascospores and liberated ascospores (indicated by arrow). l,m Metschnikowia bicuspidata (Metschnikowiaceae, Serinales, Pichiomycetes). (l) M. bucuspidata var. californica budding cells and needle-shaped ascospores. (m) M. bucuspidata var. chathamia budding cells and needle-shaped ascospores. n Saccharomyces cerevisiae (Saccharomycetaceae, Saccharomycetales, Saccharomycetes) budding cells and unconjugated, persistent ascus with globose ascospores (indicated by arrow). o, p Phaffomyces opuntiae (Phaffomycetaceae, Phaffomycetales, Saccharomycetes). (o) Budding cells and asci with hat-shaped ascospores (indicated by arrows). (p) Budding cells in short chains and asci with hat-shaped ascospores (indicated by arrows). q Saccharomycodes ludwigii (Saccharomycodaceae, Saccharomycodales, Saccharomycetes) bipolar cell division of budding cells and asci with spherical ascospores (indicated by arrows). r-t Ascoidea rubescens (Ascoideaceae, Ascoideales, Saccharomycetes). (r) Asexual cells and cluster of ascospores (indicated by arrow) (s) Asexual cells and septate hyphae, (t) Ascus with spores in different states of nascendi. u Sporopachydermia lactativora (Sporopachydermiaceae, Sporopachydermiales, Sporopachydermiomycetes) budding cells. v Trigonopsis variabilis (Trigonopsidaceae, Trigonopsidales, Trigonopsidomycetes). Budding cells with ellipsoidal and triangular morphology. Triangular cells produce ellipsoidal and triangular buds. Scale bar: a = 5μm, b-q, u,v = 10μm, r-t =30μm.
References
Kurtzman CP, Fell JW. 1998 – The yeasts – a taxonomic study, 4th edn. Elsevier, Amsterdam
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 25 September 2026