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

Sphaeria ribesia Pers., Ann. Bot. (Usteri) 11: 24 (1794)

Parasitic or saprobic on wood and twigs in terrestrial habitats. Sexual state: Ascostromata (683−)955 × 1257(−1297) µm, black, immersed, becoming erumpent thorough bark at maturity, solitary or scattered, globose to subglobose, coriaceous, multiloculate, with many locules, cells of ascostromata composed of several layers of dark brown to black cells of textura angularis. Locules 408−413 μm high × (76−)84−115(−122) µm diam. ( = 410.5 × 93 µm, n = 10), subglobose to obpyriform, arranged at the periphery 1 to 2 layers of locules, evidently ostioles at the surface. Peridium of locules thick, cell layers with ca. 11 µm thick, composed of dark brown to lightly pigmented cells of textura prismatica and angularis. Hamathecium lacking pseudoparaphyses. Asci (108.5−) 111−123 (−125) × 13−16 (−18) µm (= 116 × 15 µm, n = 15), 8-spored, bitunicate, oblong, cylindrical to subclavate, pedicellate, and rounded at the apex with a flattened ocular chamber ca. 2.5 µm wide, stalks ca. 16 μm long. Ascospores (20−)23−30.5(−32) × 7−9.5(−10) µm (= 26 × 8.5 µm, n = 25), overlapping, uni to biseriate, hyaline, broadly fusiform, rounded at both ends, with upper broad cell, 1-septate, with a median septum, constricted at the septum,  smooth. Asexual state: Unknown.

Material examined: CZECH REPUBLIC, Böhmen, Tabor, on Ribes rubrum L. (Grossulariaceae), April 1904, Fr. Bubák (BPI 642930).

Fig. 1 Plowrightia ribesia (BPI 642930). a Herbarium material. b Ascostromata on the host surface. c Partial section through ascostromata. d Close up of the locules. e, f Asci. g, h Ascospores. Scale bars: b = 1000 µm, c, d = 100 µm, e, f = 50 µm, g, h = 20 µm.

Description of Plowrightia ribesia (MFLU 14−0040)

Saprobic on woody plants. Sexual state: Ascostromata 1−1.3 mm high × 0.45−0.53 mm diam ( = 1.23 × 0.48 mm, n = 10), black, superficial or semi-immersed to erumpent, solitary, scattered, or sometimes gregarious, globose to subglobose, coriaceous, multiloculate, with 10−13 locules, cells of ascostromata composed of dark brown-walled of textura angularis. Locules (= 131× 98 μm, n = 10), globose to subglobose, non-ostiolate. Peridium of locules 15−31 μm ( = 21 μm, n = 7), comprising few layers of lightly pigmented to brown cells of textura angularis. Hamathecium lacking pseudoparaphyses. Asci 81−122 × 11−17 μm ( = 98 × 14 μm, n = 10), 8-spored, bitunicate, fissitunicate, clavate, with a short pedicel, thick-walled, rounded at the apex. Ascospores 18−28 × 5−11 μm (= 23 × 8 μm, n = 10), uniseriate, partially overlapping, hyaline, 1-septate, constricted at the septum, upper cell often broader than the lower cell, fusiform to ellipsoid, gradually tapering towards the apex, smooth-walled. Asexual state: Unknown.

Culture characteristics: Ascospores germinating on PDA within 12 h and germ tubes arise from both end cells. Colonies growing fast on PDA, reaching a diam. of 3 cm after 5 days at 29 °C, velvety, radiating towards the edge. Mycelium initially hyaline and light pink at the margin.

Material examined: ITALY, Fonte al Fringuello – Pratomagno (Province of Arezzo

[AR]), on dead and not land branch of Daphne sp. (Thymelaeaceae), 10 May 2013, Camporesi Erio (MFLU14−0040), living culture MFLUCC 13−0670.

Fig. 2 Plowrightia ribesia (MFLU 14−0040). a, b. Ascostromata on the host surface. c-e. Vertical section through ascostromata. f. Close up of of the peridium of locus. g-j. Asci with ascospores. k. Germination of ascospore. l-p. Ascospores. q. Colonies on PDA from above and r blow. Scale bars: b =1000 µm, c = 100 µm, d = 50 µm, e, f = 20 µm, g-k= 10 µm, l-p = 5 µm.

Notes: Plowrightia ribesia (Sphaeria ribesia Pers.) was introduced by Saccardo (1883) as the type specimen of Plowrightia.We could not loan the holotype of Plowrightia ribesia (Pers.) Sacc., but observed a specimen from BPI (BPI 642930) from the Czech Republic. This was compared with our recent collection from Italy from dead branches of Daphne sp. and is indistinguishable. Plowrightia ribesia is widely distributed in Europe and is parasitic on Ribes rubrum (Grossulariaceae) (Saccardo 1883; Hoggan 1927). Since the host of the MFLU specimen from Italy is from Daphne sp. (Thymelaeaceae) and not Ribes we have not designated this as an epitype. However, this strain can be considered as an authentic until proven otherwise.