Myxocyclus
Myxocyclus Riess, in Fresenius, Beitr. Mykol. 2: 62 (1852).
Index Fungorum number: IF 9053; Facesoffungi number: FoF 06434, 1 morphological species (Species Fungorum 2022), 1 species with molecular.
Endophytic or saprobic on twigs or bark of Pinaceae (Gymnosperm) and Betulaceae (Dicotyledons). Sexual morph: Splanchnonema sensu lato Tanaka et al. (2005). Asexual morph: Conidiomata acervular or pycnidial, subperidermal, immersed, erumpent at maturity, solitary, punctiform, dark brown to black. Conidiomata outer wall composed of thick-walled, dark brown walled cells of textura angularis, inner wall composed of thin-walled, pale brown cells of textura angularis. Conidiophores cylindrical, flexuous, septate, branched at the base, pale brown, verruculose, hyaline at the apex, enclosed in a gelatinous sheath. Conidiogenous cells holoblastic, cylindrical, integrated, determinate, pale brown to hyaline, smooth. Conidia clavate to pyriform, tapered to the base, apex obtuse, muriform, verruculose, 7–8-distoseptate, constricted, with longitudinal or oblique distosepta, lumina reduced, guttulate, enclosed in a gelatinous sheath (adapted from Sutton 1980, Wijayawardene et al. 2016).
Type species: Myxocyclus confluens Riess
Notes: Myxocyclus is characterised by acervular or pycnidial, subperidermal, dark brown conidiomata, cylindrical, flexuous, septate conidiophores, holoblastic, cylindrical, integrated conidiogenous cells and clavate to pyriform, verruculose, 7–8-distoseptate conidia. Sutton (1975, 1977, 1980) considered Hendersonia polycystis as the oldest name of the taxon and transferred M. polycystis to Myxocyclus. The authors also treated M. polycystis as the type species of Myxocyclus and considered M. confluens as its synonym. Petrak (1927) added another species M. cenangioides to Myxocyclus but this was rejected by Sutton (1980) who stated that M. cenangioides is not congeneric with the type species of Myxocyclus. Saccardo (1908) and Barr (1982) suggested Splanchnonema argus is the sexual morph of Myxocyclus polycystis based on the co-occurrence of both morphs on same host. Tanaka et al. (2005) confirmed the sexual and asexual morph of Myxocyclus using culture techniques. Wijayawardene et al. (2016) did not reduce Myxocyclus under Splanchnonema for several reasons. Firstly, Splanchnonema argus is not the type species of Splanchnonema. Secondly, molecular data for Splanchnonema argus is lacking and thirdly, there is no evidence that S. argus is congeneric with Splanchnonema s. str.. Myxocyclus lacks sequence data hence the taxonomic placement of the genus is doubtful. Myxocyclus is currently considered as a distinct genus in Pleomassariaceae but fresh collections are needed to confirm this taxonomic placement. Only LSU sequence data is available for a strain of M. polycystis (CBS 222.77).
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