Acrotheca
Acrotheca Fuckel, Jb. nassau. Ver. Naturk. 15: 42 (1860).
Index Fungorum number: IF 7047; Facesoffungi number: FoF 08578, 5 morphological species (Species Fungorum 2022), 1 species with molecular data.
Leaf spots amphigenous, subcircular, angular to irregular, sometimes oblong, at first pale greenish, yellowish-ochraceous, later brown, margin indefinite or usually with narrow darker border, brownish or purplish. Sexual morph: Unknown. Asexual morph: Caespituli amphigenous, greyish white, punctiform. Mycelium internal, hyphae hyaline, septate, sparsely branched, forming small to well-developed substomatal stromata, at first colorless, later usually pigmented. Conidiophores in small to rich fascicles, loose to dense, erect, straight, subcylindric to geniculate-sinuous, apically sometimes subdenticulate, simple, aseptate or with a few septa, hyaline, long conidiophores occasionally somewhat pigmented at the very based near stromata, short conidiophores sometimes pale olivaceous throughout, smooth, conidial scars somewhat thickened, darkened. Conidia catenate, occasionally in branched chains, ellipsoid-ovoid, subcylindric-fusoid, 0–1(–2)-septate, hyaline, almost smooth to verruculose, ends obtuse to subacute, hila slightly thickened and darkened (adapted from the description of Ramularia gei in Braun 1998).
Type species: Acrotheca gei Fuckel
Notes: Acrotheca is characterised by amphigenous, greyish white caespituli, subcylindric to geniculate-sinuous conidiophores, and ellipsoid-ovoid, subcylindric-fusoid, 0–1(–2)-septate conidia. Acrotheca gei was previously considered as a species of Ramularia but this was not proven based on molecular data. Hughes (1953) mentioned that Acrotheca gei and Ramularia gei are identical. Ramularia gei was originally found on Geum urbanum (Rosaceae) from Sweden with the holotype deposited in S herbarium. In the phylogenetic analysis of Videira et al. (2016) based on rpb2, ITS, actA, gapdh, tef1-α, the strains of R. gei (CBS 344.49 on Geum urbanum in Netherlands) and (CBS 113977 on Geum sp. in Sweden) formed a highly supported clade in Mycosphaerellaceae. Videira et al. (2016) stated that these two strains are sterile in culture and the herbarium specimen is in poor condition. The placement of Acrotheca in Mycosphaerellaceae is doubtful. Fresh collections with DNA sequence data are needed to confirm the generic placement.
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