Spilosphaeria Rabenh., Klotzschii Herb. Viv. Mycol., Edn Nov, Ser. Sec., Cent. 5: no. 442a (1857).
Associated with leaf spot. Sexual morph: Unknown. Asexual morph: Conidiomata pycnidial, mostly epiphyllous, subglobose to lenticular, not protruding strongly, brown to almost black. Ostiole central, initially circular and surrounding cells concolorous to rather darker brown. Conidiomatal wall composed of angular cells, the outermost cells pale yellowish brown with somewhat thickened walls, the inner cells thin-walled. Conidiogenous cells hyaline, discrete, narrowly or broadly ampulliform with a relatively wide neck, holoblastic, often first proliferating sympodially, and later also percurrently 1–several times with distinct annellations. Conidia filiform to filiform-cylindrical, straight or slightly curved, or flexuous, attenuated gradually to a narrowly rounded to pointed apex, attenuated more abruptly towards the truncate base, 1–4-septate, not or only inconspicuously constricted around the septa, hyaline, contents with several minute oil-droplets and granular material in each cell in the living state, with inconspicuous oil-droplets and granular contents in the rehydrated state (adapted from description of Septoria polygonorum in Verkley et al. 2013).
Type species: Spilosphaeria polygonorum (Desm.) Rabenh.
Notes: Spilosphaeria is characterised by pycnidial, mainly epiphyllous conidiomata, central ostiole, pale yellowish brown conidiomatal wall, narrowly or broadly ampulliform conidiogenous cells and filiform to filiform-cylindrical, straight or slightly curved conidia. Spilosphaeria polygonorum was previously known as Septoria polygonorum but is not congeneric with the type species of Septoria, S. cytisi. Muthumary (1999) re-examined the type specimen of S. polygonorum from PC and reported sympodial proliferated conidiogenous cells. Priest (2006) described the conidiogenous cells of S. polygonorum as holoblastic (first conidium), forming successive conidia enteroblastically, separating at the same level. Verkley et al. (2013) provided an updated description and illustration of Septoria polygonorum and also reported sympodially proliferating conidiogenous cells. In the phylogenetic analysis of Verkley et al. (2013) based on Act, Cal, EF1, RPB2, Btub, ITS and LSU, the strains S. polygonorum CBS 102330, CBS 347.67, CBS 102331, CBS 109834, CBS 113110 and CBS 108982 grouped together. Spilosphaeria was regarded as a synonym of Septoria based on morphology. There is insufficient information regarding Spilosphaeria. The placement of Spilosphaeria in Mycosphaerellaceae is doubtful. Spilosphaeria needs epitypification. Fresh collections with DNA sequence data are needed to confirm the taxonomic placement of Spilosphaeria.