Thyrostroma

Höhn., Sitzungsber. Kaiserl. Akad. Wiss., Math.-Naturwiss. Cl., Abt. 1 120: 472 (94 repr.). 1911.

• Classification: Dothideomycetes, Pleosporomycetidae, Pleosporales, Dothidotthiaceae.
• Type species: Thyrostroma compactum (Sacc.) Höhn. Holotype could not be located, and a neotype from Europe is required 
• DNA barcode (genus): LSU. 
• DNA barcodes (species): ITS, tef1.

Sexual morph unknown. Conidiomata sporodochial, punctiform, dark brown or black. Stroma immersed to superficial, brown. Conidiophores brown, finely roughened, cylindrical to subcylindrical, 1–3-septate. Conidiogenous cells brown, subcylindrical, finely roughened, proliferating percurrently at apex. Conidia cylindrical, clavate, or ellipsoid to fusoid, pale to medium brown, smooth-walled, with (1–)4 transverse septa, and 0–3 oblique or longitudinal septa, rounded at the apex, base truncate.

Culture characteristics:

Colonies reaching 90 mm diam after 2 wk, with sparse or fluffy aerial mycelium. Colonies on MEA, PDA and OA showing different shades of grey or chestnut to umber colour.

Optimal media and cultivation conditions:

MEA, PDA and OA at 25 °C.

Distribution:

Asia, Europe and North America.

Hosts:

Pathogens of Ulmus spp., Sambucus caerulea, Styphnolobium japonicum, Tilia spp., and Cornus officinalis.

Disease symptoms:

Thyrostroma canker, dieback and leaf spots.

Notes:

Thyrostroma was introduced in 1911 in order to accommodate T. compactum (von Höhnel 1911). Despite being described more than 100 years ago, the phylogenetic position of Thyrostroma remains unresolved. Thyrostroma was considered the asexual morph of Dothidotthia by Phillips et al. (2008). Subsequently, Slippers et al. (2013) placed Thyrostroma in the Botryosphaeriaceae based on morphology, since molecular data of Thyrostroma spp. were lacking. In the phylogenetic trees based on LSU sequences (Fig. 49), the type species of Thyrostroma, T. compactum, does not cluster with Dothidotthia (Dothidotthiaceae), demonstrating that these genera are not congeneric, as was recently mentioned by Crous et al. (2016). However, Thyrostroma did cluster in the Dothidotthiaceae clade, as originally proposed by Phillips et al. (2008).

References:

• Ellis 1959, 1971, Crous et al. 2016 (morphology).
• Crous PW, Wingfield MJ, Richardson DM, et al. (2016c). Fungal Planet description sheets: 400–468. Persoonia 36: 316–458.
• Ellis MB (1959). Clasterosporium and some allied Dematiaceae - Phragmosporae. II. Mycological Papers 72: 1–72.
• Ellis MB (1971). Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, UK.
• Phillips AJL, Alves A, Pennycook SR, et al. (2008). Resolving the phylogenetic and taxonomic status of dark-spored teleomorph genera in the Botryosphaeriaceae. Persoonia 21: 29–55.
• Slippers B, Boissin E, Phillips AJ, et al. (2013). Phylogenetic lineages in the Botryosphaeriales: a systematic and evolutionary framework. Studies in Mycology 76: 31–49.
• von Höhnel F (1911). Fragmente zur Mykologie. XIII Mitteilung (Nr. 642 bis 718). Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften Math.-naturw. Klasse Abt. I. 120: 379–484.

Table 20. DNA barcodes of accepted Thyrostroma spp.

¹CBS: Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands. ^T indicates ex-type strains.

²ITS: internal transcribed spacers and intervening 5.8S nrDNA; tef1: partial translation elongation factor 1-alpha gene.

• Crous PW, Wingfield MJ, Richardson DM, et al. (2016c). Fungal Planet description sheets: 400–468. Persoonia 36: 316–458.
• Marin-Felix Y, Groenewald JZ, Cai, L, et al. (2017). Genera of phytopathogenic fungi: GOPHY 1. Studies in Mycology xxxx.