Thyrostroma
Thyrostroma Höhn., Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften Math. - naturw. Klasse Abt. I 120: 472 (1911).
Index Fungorum number: IF 10224; Facesoffungi number: FoF 07941, 24 morphological species (Species Fungorum 2022), 12 species with molecular data.
Saprobic, pathogenic on leaves and wood in terrestrial habitats. Sexual morph: Ascostromata pseudothecial, immersed, raised, erumpent to superficial, breaking through host surface, ruptured, rounded, elongate, lenticular, or irregular in shape, uni- to multi-loculate, glabrous, ostiolate, apapillate. Ascomata immersed in ascostroma, dark brown to black, clustered, gregarious, rarely solitary, globose to subglobose, ostiole central, apapillate. Peridium thin- to thick-walled of unequal thickness, thicker at the apex, thinner at the base, with several cell layers of textura angularis, outer layer comprising brown to black, inner layer comprising hyaline to pale brown cells. Hamathecium composed of dense, hyaline, septate pseudoparaphyses. Asci 8-spored, bitunicate, fissitunicate, clavate, short pedicellate, apically rounded, with well-developed ocular chamber. Ascospores, pale brown, fusiform to ellipsoidal, with rounded ends, uniseptate, constricted at the septum. Asexual morph: Colonies stromatic, sporodochial, immersed to erumpent, breaking through host surface, ruptured, convex to applanate, or pulvinate, lenticular, or irregularly dehiscent, dark brown to black. Conidiophores macronematous, cylindrical to subcylindrical, septate, branched, hyaline to brown, arising from basal pseudoparenchymatous sporodochia. Conidiogenous cells holoblastic, monoblastic, polyblastic, integrated, terminal. Conidia acrogenous, straight or curved, variable in shape, clavate, ellipsoidal, obpyriform, subglobose, or oblong to subcylindric-clavate, phragmosporous to muriform, rounded at the apex, tapered or truncate at the base, with 1–8 transverse septa, and 0–6 longitudinal septa, pale to dark brown, constricted at the septa, rough-walled, echinulate (adapted from Senwanna et al. 2019).
Type species: Thyrostroma compactum (Sacc.) Höhn.
Notes: Thyrostroma is characterised by pseudothecial, immersed, raised, erumpent to superficial ascostromata, globose to subglobose ascomata, clavate, short pedicellate asci and pale brown, fusiform to ellipsoidal ascospores. The asexual morph is characterised by stromatic, sporodochia colonies, macronematous, cylindrical to subcylindrical conidiophores, holoblastic, monoblastic, polyblastic conidiogenous cells and clavate, ellipsoidal, obpyriform, or subglobose conidia. Ramaley (2005) mentioned Dothidotthia as the sexual morph of Thyrostroma based on the formation of hyphomycetes in culture from asci. Slippers et al. (2013) referred Thyrostroma to Botryosphaeriaceae based on morphology. This sexual and asexual link has not been proven by molecular data hence, Wijayawardene et al. (2014) recommended to use both names. In the phylogenetic analysis of Marin-Felix et al. (2017) based on LSU sequence data, Thyrostroma formed a distinct lineage in Dothidotthiaceae, which was in agreement with Phillips et al. (2008). Marin-Felix et al. (2017) also reported that Thyrostroma is phylogenetically distinct from Dothidotthia in Dothidotthiaceae and hence the genera are not congeneric. In the phylogenetic analyses of Senwanna et al. (2019) based on a combined dataset of LSU, SSU, ITS and TEF1-α sequence, Thyrostroma formed a distinct lineage from Dothidotthia in Dothidotthiaceae with strong statistical support. Senwanna et al. (2019) added eight species to Thyrostroma based on morphology and phylogenetic evidence. Senwanna et al. (2019) also reported the first record of sexual morph in Thyrostroma based on T. ulmicola. Thyrostroma is morphologically and phylogenetically a distinct genus in Dothidotthiaceae. Molecular markers available for Thyrostroma are ITS, LSU, SSU, Actin, BTUB, RPB2 and TEF-1.
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