Botryosphaeriales » Saccharataceae

Pileospora

Pileospora J.B. Tanney & K.A. Seifert, Mycol. Prog. 18: 169 (2019).

Index Fungorum number: IF 824738; Facesoffungi number: FoF 11899, 1 morphological species (Species Fungorum 2022), 1 species with molecular data.

Colonies flat, with sparse aerial hyphae; margin diffuse, hyaline; surface and reverse white; exudates and soluble pigments absent; mycelium consisting of hyaline, smooth, septate, branched, hyphae. Sexual morph: Unknown. Asexual morph: Conidiomata on MEA pycnidial, scattered, single, or clustered in small groups of 2–4, submersed in agar then erumpent with maturity, dark brown to black, uniloculate, subglobose to globose. Pycnidial wall typically composed of two layers: outer layer dark, comprised of thick-walled, dark brown textura angularis; inner layer hyaline, comprised of thin-walled cells. Paraphyses not evident. Conidiophores lining the inner pycnidial wall, cylindrical, hyaline, smooth, thin-walled, septate, sparingly branched or reduced to conidiogenous cells. Conidiogenous cells cylindrical, smooth, holoblastic, phialidic with prominent periclinal thickening, giving rise to dimorphic conidia. Type 1 conidia hyaline, smooth, ellipsoidal-fusiform to broadly cylindrical-fusiform, apex subobtuse with irregular mucoid appendages (type C; Nag Raj 1993), base broadly to acutely rounded or subtruncate, aseptate, thin-walled, guttulate, appearing granular, exuded in colorless droplet. Type 2 conidia formed in the same conidioma as type 1 conidia, often produced in the upper portion of pycnidium towards ostiole, hyaline, smooth, variable in shape, subglobose to globose, pyriform, ossiform, fusiform-cylindrical, without appendages, aseptate, thin-walled, exuded in colorless droplet with type 1 conidia (adapted from Tanney & Seifert 2019).

 Type species: Pileospora piceae Tanney & Seifert

Notes: Pileospora is characterised by pycnidial, scattered conidiomata, cylindrical, hyaline, smooth, thin-walled conidiophores, cylindrical, smooth, holoblastic, phialidic conidiogenous cells and two types of conidia. Type 1 conidia are hyaline, smooth, ellipsoidal-fusiform, while type 2 conidia are formed in the same conidiomata but are pyriform, ossiform and fusiform-cylindrical. Pileospora morphologically resembles members of Neofusicoccum, Saccharata, and other genera of Botryosphaeriales in having fusicoccum-like asexual morph cooccurring with irregularly-shaped conidia which might be spermatia. Pileospora differs from other similar morphologically genera in having an irregular mucoid apical appendage. In the phylogenetic analysis of Tanney and Seifert (2018) based on ITS and LSU sequence data, P. piceae clusters in a polytomy comprising members of Saccharataceae and Septorioideaceae. Pileospora morphologically differs from Septorioides in having aseptate, ellipsoidal-fusiform conidia with apical appendages while Septorioides has subcylindrical to fusiform-ellipsoidal, 1–10-septate conidia without appendages. Both Pileospora and Septorioides have same ecology occurring as an endophyte in conifer needles but the former is known from Picea mariana and P. rubens needles while Septorioides is reported only from Pinus needles. Tanney and Seifert (2018) mentioned that Pileospora might be a synonym of Botryosphaeria since Funk (1965) described Botryosphaeria piceae from Picea sitchensis cankers and Picea glauca but this is not confirmed yet. Tanney and Seifert (2018) re-studied the isotype specimen of B. piceae (DAOM 105936) but did not find any asexual morph indicative to Pileospora. Pileospora is morphologically and phylogenetically a distinct genus in Saccharataceae. Molecular markers available for Pileospora include ITS, LSU and TEF-1.

 

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