Pseudocercosporella Deighton, Mycol. Pap. 133: 38 (1973).
Index Fungorum number: IF 9560; Facesoffungi number: FoF 08552, 96 morphological species (Species Fungorum 2022), 13 species with molecular data.
Associated with leaf spot. Sexual morph: Unknown. Asexual morph: Colonies in vivo. Mycelium consisting of primary internal and secondary external hyphae, hyaline to pale brown, septate, branched, smooth; stromata lacking or weakly to well-developed, substomatal to intraepidermal. Conidiophores solitary to fasciculate, emerging through stomata or erumpent through the cuticle, arising from inner hyphae or from stromata, sometimes formed as lateral branches of superficial hyphae, or forming crustose to subglobose sporodochia; conidiophores rarely branched, straight and subcylindric to geniculate-sinuous, hyaline, occasionally faintly pigmented, reduced to conidiogenous cells, or septate. Conidiogenous cells integrated, terminal, mono- to polyblastic; conidiogenous loci inconspicuous, unthickened, hyaline. Conidia formed singly, rarely in simple or branched chains, subcylindrical, filiform, somewhat obclavate, euseptate, 1–multi-septate, hyaline, thin-walled, apex obtuse to subacute, base subtruncate, hilum unthickened, not darkened, nor refractive (adapted from Frank et al. 2010; Videira et al. 2017).
Type species: Pseudocercosporella ipomoeae Sawada ex Deighton
Notes: Pseudocercosporella is characterised by substomatal to intraepidermal mycelium, solitary to fasciculate conidiophores, integrated, terminal, mono- to polyblastic conidiogenous cells and subcylindrical, filiform, somewhat obclavate, euseptate, 1–multi-septate, hyaline conidia. Pseudocercosporella previously accommodated asexual morphs of the Mycosphaerella complex that were Cercosporella-like, but had unthickened and inconspicuous conidial scars (Videira et al. 2017). Nirenberg (1981), Robbertse et al. (1995) and Lucas et al. (2000) accommodated four cercosporoid species which were linked with eyespot disease of cereals in Pseudocercosporella but Arx (1983) transferred those taxa to Ramulispora. Braun (1995) re-examined the type specimens of Pseudocercosporella bakeri and P. ipomoeae and reported that they are one taxon. Frank et al. (2010) agreed with the observation of Braun (1995) and designated an epitype for Pseudocercosporella bakeri. In the phylogenetic analysis of Videira et al. (2017), Pseudocercosporella based on a strain of P. bakeri formed a well-supported clade close to Asperisporium and Amycosphaerella in Mycosphaerellaceae. Ideal molecular makers to differentiate or introduce species of Pseudocercosporella are LSU and ITS sequence data but rpb2 gives greater resolution. Videira et al. (2017) transferred several species which are pseudocercosporella-like in morphology but are phylogenetically not congeneric with the type species of Pseudocercosporella to other genera. Pseudocercosporella is a distinct genus in Mycosphaerellaceae but morphology alone is inadequate to introduce new species of Pseudocercosporella. Molecular markers available for Pseudocercosporella are ITS, LSU, Actin, BTUB, Calmodulin, Histone, RPB2 and TEF-1.
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