Strigulales » Strigulaceae

Racoplaca

Racoplaca Fée, Essai Crypt. Exot. (Paris): lxviii, xciv, xcix (1825); Jiang et al., Fung. Div. 102: 285.

Index Fungorum number: IF 4640; Facesoffungi number: FoF 08888, 5 morphological species (Species Fungorum 2022), 2 species with molecular data.

Thallus foliicolous, crustose, subcuticular, typically laciniate, composed of dichotomously branched lobes that form an attractively patterned radiating reticulum, individual lobes bordered by thin, black line. Photobiont Cephaleuros. Sexual morph: Perithecia prominent, wart-shaped to conical, usually covered by a thin thallus layer up to the ostiole, therefore not pure black; excipulum prosoplectenchymatous, colorless; involucrellum carbonized, black; hamathecium colorless, I–, KI–; paraphyses unbranched, thin. Asci bitunicate, with short tholus and narrow, ocular chamber, I–, KI–, clavate to oblong. Ascospores 8 per ascus, 2-seriate or irregularly arranged, oblong to fusiform, uniseptate, colorless. Asexual morph: Pycnidia immersed-erumpent to adnate, wart-shaped to conical, usually black. Macroconidia bacillar to filiform, uniseptate, colorless, both ends with short gelatinous appendages (10–25 μm, not exceeding 50 μm even after prolonged time in squash mounts). Microconidia fusiform-ellipsoid non-septate, colorless Chemistry: No substances detected by TLC (adapted from Jiang et al. 2020).

 Type species: Racoplaca subtilissima Fée

Notes: Racoplaca is characterised by prominent, wart-shaped perithecia, clavate to oblong asci and oblong to fusiform, uniseptate, colorless ascospores. The asexual morph is characterised by wart-shaped to conical, usually black pycnidia, bacillar to filiform, uniseptate macroconidia and fusiform-ellipsoid non-septate, colorless microconidia. Jiang et al. (2020) provided four combinations namely Racoplaca maculata, R. melanobapha, R. transversoundulata and R. tremens and re-instated Racoplaca for taxa of the Strigula subtillissima group, characterised by thin, laciniate thalli with the margins bordered by a thin, black line. Racoplaca is morphologically and phylogenetically a distinct genus in Strigulaceae. Molecular markers available for Racoplaca include R. melanobapha (ITS, SSU, RPB2, TEF-1) and R. subtilissima (SSU, TEF-1).

 

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