Plowrightia Sacc., Syll. fung. (Abellini) 2: 635 (1883).

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 lacking 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 notes.

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 specimen 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 DothideaceaePlowrightia 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 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.

Type species: Plowrightia ribesia (Pers.) Sacc., Syll. fung. (Abellini) 2: 635 (1883).