Dothidasteroma
Dothidasteroma Höhn., Sber. Akad. Wiss. Wien, Math.- naturw. Kl., Abt. 1 118: 1509 (1909).
Index Fungorum number: IF 1691; Facesoffungi number: FoF 08114, 4 morphological species (Species Fungorum 2022), no molecular data available.
Symptoms scattered or confluent leaf spots, mostly epiphyllous less frequently hypophyllous, elliptical or circular to irregular, brown to dark brown with pale reddish-purple borders; along the midrib colonies appear amphigenous as elliptical or elongate dark lesions, containing an aggregation of black conspicuous discoid stromata with a central opening that splits in a stellar fashion when wet. Mycelium internal, conspicuous, hyaline, filamentous; hyphae emanating from internal hypostromata towards the cuticle where stromatic erumpent ascomata are formed. Sexual morph: Stromata subcuticular, intracuticular to intradermal, sparse to extensive, mostly one-layered; cells brown to dark brown. Ascomata originating from the immersed stromata, scutate, variable in shape, usually circular, brown to dark brown, confluent, opening by irregular fissures. Upper surface composed of pale to dark brown cells that proliferate per currently in a dichotomous fashion resulting in textura prismatico-radiata, with a crenate to laciniate margin; upper wall dense, brown, thick; locules single, initially filled by the hamathecium that partially change into a gelatinous mucus as the asci develop. Hamathecium of filiform branched paraphyses initially filling the locules, but mostly evanescing as the asci develop, colorless, septate, thin-walled, slightly bulbous at the tip. Asci maturing sequentially, with young and mature individuals in the same locule; young asci obovoid, clavate to broadly clavate, becoming thick-walled particularly in the upper part; full-size asci with colorless spores, clavate to broadly clavate, thick-walled particularly in the upper part, J–, with 8 spores arranged in two rows or in a cluster; full-size asci with brown mature spores. Ascospores initially colorless, guttulate, becoming light brown to brown, ellipsoidal to cylindric-ellipsoidal, thin-walled, smooth, uniseptate, constricted at the septum, lower cells, tapering towards the base; upper cell globose. Asexual morph: Unknown (adapted from Inácio et al. 2011).
Type species: Dothidasteroma pterygotae (Berk. & Broome) Höhn.
Notes: Dothidasteroma is characterised by scattered or confluent leaf spots, subcuticular, intracuticular to intradermal stromata, filiform branched paraphyses, clavate to broadly clavate asci, and colorless, guttulate, smooth, uniseptate ascospores. Dothidasteroma resembles Aulacostroma but differs in that the latter has superficial mycelium with bulbous apressoria while Dothidasteroma lacks superficial hyphae or hyphal strands. Dothidasteroma also resembles Mintera in producing an effuse brown internal stroma attached to the superficial ascomata with small peg-like columns but differs in that the latter has superficial appressoriate mycelium and ascomata with radiating locules which is lacking in Dothidasteroma (Inácio & Cannon 2003). Dothidasteroma is also similar to members of Asterinaceae namely, Dothidasteromella, Macowaniella, and Echidnodes in having immersed stromatic structures but differs in that these three genera form a well-developed hyphopodiate superficial mycelium (Inácio & Cannon 2008). Inácio and Cannon (2008) provided an updated account of Dothidasteroma and accepted three species. Inácio et al. (2011) added a fourth species D. psidii isolated from a myrtaceous host from South America and provided a key to accepted species of Dothidasteroma. Dothidasteroma is a distinct genus in Parmulariaceae but molecular data is lacking. Fresh collections with DNA sequence data are needed to confirm the taxonomic placement of Dothidasteroma.
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