Pleosporales » Fusculinaceae

Fusculina

Fusculina Crous & Summerell, in Summerell et al., Fungal Diversity 23: 334 (2006).

 Index Fungorum number: IF 510010; Facesoffungi number: FoF 08243, 3 morphological species (Species Fungorum 2022), 3 species with molecular data.

Leaf spots amphigenous, circular, medium brown with a raised border, 2– 6 mm diam. Sexual morph: Unknown. Asexual morph: Mycelium predominantly internal, but external hyphae brown, thick-walled, rough, giving rise to chlamydospore-like cells; conidia exuding in a hyaline mass; two conidial types other than chlamydospores present on host material as well as in culture. Conidiomata amphigenous, black on leaves, pycnidial, immersed, becoming slightly erumpent, brown under light microscope, but upper region appearing crust-like, dark-brown; opening by irregular rupture; wall consisting of 2–4 layers of brown cells of textura angularis that give rise to 2–4 layers of hyaline cells. Conidiomata forming on OA in culture, exuding creamy masses of conidia, with visible strands of dark-brown, thick-walled chlamydospore-like cells formed intercalary in aerial mycelium; upper, outer region of conidiomata crust-like, dark-brown, distinct from brown, smooth conidiomatal body; conidiomata opening by irregular rupture; apical region containing long, subcylindrical, hyaline, septate periphysoids, up to 50 µm long, 2–3 µm wide, extending half way down the conidioma, where they are replaced by conidiogenous cells of two types. Primary conidiogenous cells hyaline, smooth, ampulliform to subcylindrical, proliferating several times percurrently near apex, giving rise to subcylindrical primary conidia. Primary conidia hyaline, granular, smooth, straight to somewhat irregular, subcylindrical, apex obtuse, base truncate. Secondary conidiogenous cells integrated among primary conidiogenous cells, hyaline, smooth, proliferating sympodially. Secondary conidia hyaline, smooth, granular, ellipsoid with rounded ends, or subcylindrical with obtuse apex and truncate base (adapted from Summerell et al. 2006).

 Type species: Fusculina eucalypti Crous & Summerell

Notes: Fusculina is characterised by amphigenous, black conidiomata, ampulliform to subcylindrical conidiogenous cells, and hyaline, granular, smooth, straight to somewhat irregular, subcylindrical conidia. In the phylogenetic analysis of Crous et al. (2018), Fusculina formed a distinct lineage close to Gordonomyces in Pleosporales and hence was accommodated in the new family Fusculinaceae. Fusculina resembles Fusicoccum complex in having hyaline, subcylindrical to rather fusoid conidia produced on percurrently proliferating conidiogenous cells (Crous et al. 2018). Fusculina is also similar to Disculina in having hyaline, aseptate conidia arising from percurrent proliferating conidiogenous cells but differs in that Fusculina has two conidial types and pycnidia while Disculina has stromatic conidiomata. Fusculina is morphologically and phylogenetically a distinct genus in Fusculinaceae. Molecular markers available for Fusculina are ITS, LSU, BTUB and TEF-1.

 

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