Pycnopeziza W.L. White & Whetzel, Mycologia 30(2): 187 (1938)
= Acarosporium Bubák & Vleugel ex Bubák, Ber. dt. bot. Ges. 29: 384 (1911)
Facesoffungi number: FoF 07550
Leotiomycetes, Leotiomycetidae, Helotiales, Sclerotiniaceae
Saprobic or parasitic on wide range of host plants, e.g., Acer rubrum, Alnus rugosa Betula pubescens, Hedera helix, Picea pungens, Populus tremuloides, Salix caprea (Sutton 1980, Nag Raj 1993). Sexual morph: see White and Whetzel (1938). Asexual morph: Conidiomata dark brown to black, stromatic, pycnidial, solitary to gregarious, initially subepidermal, becoming erumpent, globose to subglobose or irregularly collapsed, or cupulate, unilocular, glabrous, thick-walled, lacking ostiole, but dehiscing by irregular split of overlapping host tissue. Conidiomatal wall composed of thick-walled, dark brown to hyaline cells of textura angularis to textura globulosa. Conidiophores developing from the upper cells of the basal stroma in a palisade along the base of the conidiomata, hyaline, cylindrical to subcylindrical, septate, dichotomously to subdichotomously branched, smooth-walled. Conidiogenous cells hyaline, holothallic, integrated, determinate, smooth-walled. Conidia arthric, formed by disarticulation of the conidial chain, produced in complex, repeatedly branched chains with the oldest conidium at the base, hyaline, cylindrical or allantoid, initially with truncate ends, eventually becoming obtuse, 1–3-septate, smooth, bearing filiform, flexuous, attenuated, cellular appendages, arising from apical and subapical or sometime from basal region.
Type species: Pycnopeziza sympodialis W.L. White & Whetzel ex B. Sutton, The Coelomycetes: 34 (1980)
= Acarosporium sympodiale Bubák & Vleugel ex Bubák, Ber. dt. bot. Ges. 29: 385 (1911).
Notes: Acarosporium was introduced by Bubák and Vleugel in 1911, with the type species A. sympodiale, occurring on dead leaves of Betula odorata Bechst. von Höhnel (1920) introduced a new species A. austriacum Höhn., which is morphologically similar to the type taxon. Sutton (1980) subsequently synonymized A. austriacum under A. sympodiale and recognized only two species, including A. quisquiliaris W.L. White & Whetzel ex B. Sutton, the conidia of which lack appendages. Nag Raj (1993) recognized three taxa namely, A. americanum Nag Raj, A. quisquiliaris and A. sympodiale and gave a detailed account of conidium formation. Ihlen and Tønsberg (1998) and Johnston et al. (2014b) included A. lichenicola.
Acarosporium sympodiale has been connected to the sexual morph Pycnopeziza sympodialis (generic type of Pycnopeziza) (White and Whetzel, 1938, Whetzel and White 1940, Sutton 1980). Johnston et al. (2014b) synonymized Acarosporium under Pycnopeziza because it has available sequence data and the name was widely used (Holst-Jensen 1997, 2004, Wijayawardene et al. 2017b, Pärtel et al. 2017). However, lacking an available molecular sequence for the asexual morph, the relationship of these two genera remains uncertain. New collections are required to delineate the circumscription of the genus.
Distribution: Belarus, Canada, Germany, Italy, Norway, Sweden, USA (White and Whetzel 1938, Nag Raj 1993, Holst-Jense et al. 1997).
Li WJ, McKenZie EHC, Liu JK, Bhat DJ, Dai DQ, Caporesi E, Tian Q, Maharachcikumbura SSN, Luo ZL, Shang QJ, Zhang JF, Tangthirasunun N, Karunarathna SC, Xu JC, Hyde KD (2020) Taxonomy and phylogeny of hyaline-spored coelomycetes. Fungal Diversity 100: pages279–801.