Phaeotheca Sigler, Tsuneda & J.W. Carmich., Mycotaxon 12(2): 450 (1981).
Index Fungorum number: IF 9323; Facesoffungi number: FoF 07640, 5 morphological species (Species Fungorum 2022), 2 species with molecular data.
Pathogenic on twig. Asexual morph: Mycelium consisting of hyaline to brown, smooth-walled, septate, branched hyphae, that swell up in terminal or intercalary cells, and develop numerous endoconidia. Endoconidia brown, smooth to verruculose, thin- to thick-walled, globose to obovoid, aseptate to muriformly septate. Sexual morph: Unknown (adapted from Crous et al. 2018).
Type species: Phaeotheca fissurella Sigler, Tsuneda & J.W. Carmich.
Notes: Phaeotheca is characterised by hyaline to brown, smooth-walled, septate mycelium, and brown, smooth to verruculose, globose to obovoid endoconidia. Crous et al. (2016, 2018) reported that Phaeotheca is a polyphyletic genus based on phylogenetic analysis of LSU sequence data. Phaeotheca resembles several genera such as Coccidioides, Phaeothecoidea, Endoconidioma and Hyphospora in producing endoconidia but differs in a few morphological characters, mainly in their form of conidiogenesis (Seifert et al. 2011). Phaeotheca resembles Coccidioides but can be differentiated in that the latter has endospores produced from sphaerules and has alternate-arthric conidia while Phaeotheca has endoconidia produced from intercalary hyphal cells and lacks alternate-arthric conidia (Seifert et al. 2011). Phaeotheca differs from Phaeothecoidea in that the latter has verruculose, 1–2-septate endoconidia that produce endoconidia. Phaeotheca also differs from Endoconidioma in that the latter has pycnidium-like conidiomata and solitary blastoconidia while Phaeotheca lacks conidiomata. Phaeotheca also differs from Hyphospora in that the latter has hyaline mycelium and conidia and a depressed hemispheric central portion in the colony covered by hyaline hyphae in media (Ramaley 1996, Crous et al. 2018). Phaeotheca is morphologically and phylogenetically a distinct genus in its own family Phaeothecaceae. Molecular markers available for Phaeotheca are ITS, LSU, SSU, GAPDH, RPB2 and TEF-1.