Plowrightia Sacc., Syll. fung. (Abellini) 2: 635 (1883).
Index Fungorum number: IF 4262; MycoBank number: MB 4262; Facesoffungi number: FoF 00088; 17 morphological species (Species Fungorum 2020), 2 species with molecular data.
Synonyms: ≡ Elmerococcum Theiss. & Syd., Annls mycol. 13(3/4), 282 (1915)
Parasitic or saprobic on leaves, twigs, and wood in terrestrial habitats. Sexual state: Ascostromata dark brown to black, immersed, becoming erumpent through the epidermis, solitary or scattered, pulvinate, subglobose to globose, coriaceous, multiloculate, with 2 to many locules, cells of ascostromata composed of several layers of dark brown cells of textura angularis. Locules subglobose to globose, thick-walled. Peridium of locules comprising several layers of dark brown cells of textura angularis or prismatica, vertical to the host surface. Hamathecium lacks pseudoparaphyses. Asci 8-spored, bitunicate, fissitunicate, cylindrical, elongate to ellipsoid, pedicellate, rounded at the apex. Ascospores overlapping biseriate, hyaline, 1-septate, slightly constricted at septum, fusiform, subglobose to globose, tapering towards both ends, smooth-walled. Asexual state: See note.
Type species – Plowrightia ribesia (Pers.) Sacc., Syll. fung. (Abellini) 2: 635 (1883).
≡ Sphaeria ribesia Pers., Ann. Bot. (Usteri) 11: 24 (1794).
Notes – Plowrightia was introduced by Saccardo (1883) in the family Dothideaceae to accommodate P. berberidis (De Not.) Sacc., P. bullata Sacc., P. hippophaës, P. insculpta (Wallr.) Sacc., P. martianoffiana (Niessl & Thüm.) Sacc., P. mezerei (Schleich. ex Fr.) Sacc., P. morbosa Sacc., P. periclymeni (Fuckel) Sacc., P. ribesia, P. tuberculiformis (Ellis) Sacc., and P. virgultorum (Fr.) Sacc., and P. ribesia assigned as the type species. Barr (1972) synonimysed Plowrightia with Dothiora, but Von Arx and Müller (1975) and Barr (1987a) reinstated it in Dothideaceae and separated it from Dothiora based on the pulvinate, erumpent ascostromata of Plowrightia with small locules often higher than broad. Barr (1987a) transferred Plowrightia to Dothideaceae, while Hawksworth et al. (1995) and Lumbsch and Huhndorf (2010) included it in the family Dothioraceae. Recent molecular and phylogenetic studies carried out by Winton et al. (2007) also confirmed the position of Plowrightia in the family Dothioraceae. Based on their phylogenetic analysis, Winton et al. (2007) showed that Plowrightia abietis is similar to Phaeocryptopus nudus and identical to Rhizosphaera oudemansii Maubl. However, in this study, we observed the type specimens of P. nudus and P. abietis, and it is clear that they are not similar. In our phylogenetic tree, Phaeocryptopus nudus and R. oudemansii are clustered separately in two sister clades in Dothideaceae while Plowrightia abietis clustered with R. oudemansii in the same clade. Therefore, we can conclude that Plowrightia abietis and R. oudemansii are identical with the latter as the asexual state of P. abietis. However, Rhizosphaera abietis L. Mangin & Har. the type of Rhizosphaera has no molecular data and needs to be re-collected and sequenced in order to resolve the affinities of Rhizosphaera with Plowrightia in Dothideaceae. Plowrightia shares a common morphology with Dothidea. We collected P. ribesia, the type species of Plowrightia and it clustered in Dothideaceae along with other Dothidea species. Other Plowrightia species P. abietis and P. periclymeni grouped with P. nudus and Rhizosphaera species. Rhizosphaera species are also known as the asexual states of Phaeocryptopus. Conidia are unicellular but occasionally two-celled (Orton 1915). Plowrightia also produces Hormonema asexual states in culture and is classified in Venturiaceae, but grouping with Capnodiales (Winton et al. 2007). Petrak (1923b) proposed a new genus Systremmopsis with Systremmopsis ribesia as the asexual morph of Dothidea (Plowrightia) ribesia found in stromata in nature with hyaline conidia without conidiophores. Systremmopsis ribesia needs recollecting and sequencing to establish the relationship between Plowrightia ribesia and Systremmopsis ribesia.
Figure 1 – Phylogram generated from maximum likelihood analysis (RAxML) of Dothideales based on ITS, LSU and SSU sequence data. Maximum likelihood bootstrap values equal or above 70 %, Bayesian posterior probabilities equal or above 0.90 (MLBS/PP) are given at the nodes. An original isolate number is noted after the species name. The tree is rooted to Elsinoe phaseoli (CBS 165.3), E. veneta (AFTOL-ID 1853), Myriangium duriaei (AFTOL-ID 1304), and M. hispanicum (CBS 247.33). The ex-type strains are indicated in bold. Hyphen (-) represents support values below 70 % MLBS and 0.90 PP.