Sydowia Bres., Hedwigia 34(Beibl.): 66 (1895).


Pleodothis Clem., Gen. fung. (Minneapolis): 49, 173 (1909)
Plowrightia sect. Plowrightiella Sacc., Syll. fung. (Abellini) 11: 376 (1895)
Plowrightiella (Sacc.) Trotter, in Saccardo, Syll. fung. (Abellini) 24(1): 542 (1926)

Parasitic or saprobic on conifer plants or branches and wood. Sexual state: Ascostromata black, immersed to erumpent, solitary or gregarious, globose to subglobose, coriaceous, uniloculate, ostiolate. Peridium several layers thick, composed of dark brown cells of textura angularis or sometimes prismatica, more darkened on the outside, hyaline to lightly pigmented towards the interior. Hamathecium lacking pseudoparaphyses. Asci 8-poly-spored, bitunicate, fissitunicate, clavate to oblong with a short pedicel, apically rounded. Ascospores crowded to overlapping, hyaline, transversely multiseptate, constricted at the primary septum, sometimes with a vertical septum in the mid cells or rarely in the end cells, straight to inequilateral, guttulate, upper part usually wider and shorter than the lower part, elliptic, obovate, smooth. Asexual state: Hormonema and Sclerophoma (Wijayawardene et al. 2012; Hyde et al. 2013). Pycnidia stromatic, immersed at first, later erumpent, globose to irregular, solitary or aggregated, uni or multi locular or convoluted. The wall is thick and dehisces by breaking down the overlying walltissue. Conidiogenous cells phialidic, enteroblastic, determinate, discrete, hyaline to pale brown, doliiform to ampulliform, with a wide channel and minute collarette, formed from the inner cells of the wall lining the locule. Conidia hyaline, aseptate, ellipsoid, and rarely tapered at the base smooth-walled, sometimes guttulate (Sivanesan 1984).

Notes: Sydowia was formally established by Bresadola (1895) based on its gregarious ascomata in the host surface and remained monotypic until Saccardo (1899) added S. carestiae. Later, Luttrell (1973) transferred this genus into Dothioraceae based on its phragmosprous ascospores. Arx and Müller (1975) re-evaluated the bitunicate ascomycetes and placed this genus in Dothideacea based on its broad unilocular stromata and ascospores with only transverse septa. Barr (1972) and Sivanesan (1984) accepted only polysporous species in this genus. Barr (1972) accepted five species in Sydowia while Sivanesan (1984) included two. Barr (2001) accepted phragmosporous species in both 8-spored and poly-spored asci. She introduced three new phragmosporous species (S. slippii, S. taxicola and S. wolfii) which have been referred to Dothiora and S. ceanothi. Recent phylogenetic studies by Schoch et al. (2006) also proved that the placement of Sydowia in the Dothioraceae. The type species of Hormonema, Hormonema dematioides Lundberg and Melin has been suggested as the asexual state of Sydowia polyspora (Butin 1964; Cheewangkoon et al. 2009). In phylogeny analysis in Bills et al. (2004) Sydowia polyspora and H. dematioides clustered in the same clade. H. dematioides do not have the sequences of ex-type strain and also no authentic specimen has been described. We did not include this H. dematioides in our phylogenetic analysis as lack of LSU sequence data. Sequences dat of LSU and other protein coding genes and culture based analysis are required in order to confirm this relationship. Hence, we do not synonymize Hormonema under Sydowia and further investigations are suggested. Crous (in Crous et al. 2003) introduced Sydowia eucalypti (Sphaerulina eucalypti) and accommodated it in this genus based on having Sclerophoma and Hormonema synanamorphs in culture and the thick-walled ascostromata. In present phylogenetic study Sydowia eucalypti separates from the Dothideaceae clade and clusters in the Aureobasidiaceae clade with other Selenophoma species. Therefore, we exclude S. eucalypti from Sydowia and accommodate it in a new genus, Pseudosydowia. In our phylogeny analysis (Fig 1) a putative strain of Sydowia polyspora (CBS 116.29) clustered in Dothideaceae close to a putative strain of Delphinella strobiligena (CBS 735.71). Considering the close relationship of the two strains it may be that one of these two strains is wrongly identified or these two species should be in one genus as both of them are polysporous. However, we named this clade as Delphinella which comprises D. strobiligena, Rhizosphaera pini and S. polyspora pending fresh collections of Delphinella and Sydowia species. Sydowia differs from other genera of Dothideaceae in having uniloculate ascostromata. However, we accommodate Sydowia in Dothideaceae pending molecular data of the type species.

Type species: Sydowia gregaria Bres., Hedwigia 34(Beibl.): 66 (1895).