Jahniella Petr., Annls mycol. 18(4/6): 123 (1921) .
Index Fungorum number: IF 8648; Facesoffungi number: FoF 07395, 1 morphological species (Species Fungorum 2022), no molecular data available.
Saprobic on host. Mycelium branched, immersed, septate, brown. Sexual morph: Unknown. Asexual morph: Conidiomata pycnidial, superficial on epidermis, immersed, separate, globose, papillate, dark brown, thick-walled, sclerenchymatic; wall consisting of an outer layer of dark brown, thick-walled textura angularis, a middle layer of 8 cells thick, of hyaline to pale brown, thick-walled cells, and an inner layer of thin-walled, hyaline, irregular cells. Ostiole single, circular, with a distinct channel and hyaline periphysoid cells. Conidiophores reduced to conidiogenous cells. Conidiogenous cells holoblastic, determinate, discrete, hyaline, ampulliform, lining the wall of the pycnidium. Conidia straight or slightly curved, hyaline, thin-walled, smooth, 3–4-euseptate, eguttulate, truncate at the base, slightly tapered to the apex (Sutton 1980).
Type species: Jahniella bohemica Petr
Notes: Jahniella is characterised by pycnidial, superficial conidiomata with presence of single, circular ostiole, holoblastic, determinate conidiogenous cells and hyaline, thin-walled conidia. Quaedvlieg et al. (2013) examined the type specimen from K(M) 180917 and reported that the description matches that of Sutton (1980) except that the conidiomata are superficial, not immersed in the epidermis. The type species needs to be recollected to confirm the phylogenetic position of the genus. The placement of Jahniella in Mycosphaerellaceae is doubtful.
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