Dothiorella rhamni Wanasinghe, Bulgakov, E.B.G. Jones & K.D. Hyde, sp. nov.
Index Fungorum number: IF 551784, Facesoffungi number: FoF 01668, Fig. 1
Etymology: Name reflects the host genus Rhamnus, from which the species was isolated.
Holotype: MFLU 15–3541
Saprobic or weak pathogen on dead twigs of Rhamnus cathartica L. Sexual morph Undetermined. Asexual morph Conidiomata 420 – 460 μm high × 590 – 660 μm diam. (x̄ = 443.3 × 623.2 μm, n = 10), pycnidial, stromatic, mostly solitary, semi-immersed to immersed in the host, dark brown to black, ostiolate, apapillate. Peridium 50 – 60 μm wide at the base, 70 – 90 μm wide in sides, comprising 8 – 10 layers, heavily pigmented, thick – walled, comprising blackish to dark brown, angular cells, becoming flattened towards the outer layers. Conidiogenous cells 8 – 12 μm high × 4 – 6 μm wide, holoblastic, cylindrical to subcylindrical, hyaline, the first conidium produced holoblastically and subsequent conidia enteroblastically, forming typical phialides with periclinal thickenings, swollen at the base, discrete, producing a single conidium at the apex. Conidia 17 – 24 × 9 – 12μm (x̄ = 20.7 × 10.4 μm, n = 50), initially hyaline, unicellular, becoming cinnamon to sepia and 1-septate, while still attached to conidiogenous cells; detached conidia, hyaline, sepia or dark brown, unicellular or 1-septate, moderately thick-walled, wall externally smooth, roughened on the inner surface, oval to ovoid, widest in the center, apex obtuse, base truncate or rounded.
Material examined: RUSSIA, Rostov region, Oktyabrsky District, near natural sanctuary «Persianovskaya steppe», Khoruli hollow, ravine grove (47.5006484° E, 40.1385927° N), on Rhamnus cathartica (Rhamnaceae), 26 April 2014, T.S. Bulgakov (MFLU 15–3541, holotype); ex-type culture, MFLUCC 14–0902.
Notes: The genus Dothiorella was established by Saccardo (1880) to accommodate D. pyrenophora (Berk.) ex Sacc., and is characterized by branched, septate conidiophores, holoblastic conidiogenesis, and smooth to finely verruculose but not striate, brown, 1-euseptate conidia (Crous and Palm 1999). Phillips et al. (2005) re-introduced Dothiorella as a distinct Botryosphaeriaceae asexual morph with brownish conidia, which become septate while still attached to the conidiogenous cells. Dothiorella rhamni also has sepia to dark brown, 1-septate conidia, similar to other members in Dothiorella. Phylogenetically D. rhamni clustered in a sister group with D. sarmentorum (CBS 115038 and IMI 63581b) and Diplodia acerina (CBS 910.73), but D. rhamni separates from them with good statistical support.
Fig. 1 Dothiorella rhamni (holotype) a Appearance of conidiomata on host substrate b Vertical section through a conidioma c Close up of ostiole d Peridium of conidioma e, f Mature and immature conidia attached to conidiogenous cells g Mature and immature conidia h Germinated conidium. Scale bars: b = 100 μm, c, d = 20 μm, e – h = 10 μm.