Dendrostoma atlanticum Voglmayr & Jaklitsch

Jaklitsch, Walter M. & Voglmayr, Hermann, 2019, European species of Dendrostoma (Diaporthales), MycoKeys 59, pp. 1-26 : 1

Dendrostoma atlanticum Voglmayr & Jaklitsch sp. nov. Figures 3 , 4

Diagnosis.

Dendrostoma atlanticum is recognized by clay-coloured ectostromatic discs and ascospores having large guttules and bristle-like appendages.

Holotype.

France, Bretagne, Dépt. Morbihan (56), Saint Martin sur Oust, Beauvais, on twigs of Castanea sativa , soc. immature Valsaria sp., 15 Jan. 2016, A. Delannoy (WU 37024; ex-type culture CBS 145804 = D196).

Etymology.

Atlanticum , referring to its occurrence in the Atlantic region.

Description.

Sexual morph: pseudostromata 1-4.5 mm in their widest dimension in cross section, bluntly conical or pulvinate, circular, elliptic or irregular in outline, scattered, gregarious to confluent up to 7 mm length. Ectostromatic discs 0.4-2 mm in their widest dimension, distinct and conspicuous, projecting up to 0.5(-1) mm from the bark surface, pulvinate, circular, angular or fusoid in outline, with flat or convex top, initially whitish, turning pale to dark clay-coloured, splitting the periderm, often surrounded by bark flaps. Ostioles 1-40 per disc, often originating eccentrically from the perithecial venter, arranged in ring-like configuration or variably filling the disc, (44 –)100–163(– 195) µm (n = 42) in diameter at the tip, brown to black, cylindrical, sometimes attenuated towards tip, plane with the disc or projecting up to 300 µm; tip usually with dark umbilicate centre. Entostroma whitish, yellowish to pale bark coloured, consisting of thin-walled, hyaline to subhyaline 1-3 µm wide hyphae and bark cells. Perithecia (390 –)480–660(– 750) µm (n = 35) in diameter, depressed subglobose, collapsing upward upon drying; peridium ca 10-30 µm thick, colourless to pale olivaceous, consisting of hyaline to yellowish or pale brownish, thick-walled cells without clear contours, smaller and more-or-less isodiametric outside, larger and compressed inside, very variable, (3 –)4–17(– 38) in diameter (n = 66). Paraphyses of broad collapsing threads. Asci (64 –)71–86(– 90) × (11 –)13–17(– 19) µm (n = 35), fusoid to oblong, being released at maturity, containing 8 biseriate ascospores. Ascospores (13 –)15–18(– 20) × (4.3 –)5.5–7(– 8) µm, l/w (2.1 –)2.4–2.9(– 3.9) (n = 51), ellipsoid, often inequilateral, 2-celled, slightly constricted at the median septum, with the upper cell often slightly wider than the lower, hyaline, with 1-2 large and several small guttules per cell, smooth, with a hyaline, bristle-like, straight to curved appendage (10 –)11.5–15.5(– 21) × (1.5 –)2–2.5(– 2.8) µm (n = 101) at each end.

Asexual morph acervular. Conidiomata ca 1-2.2 mm in diameter, bluntly conical, width exceeding height, prosenchymatous. Covering discs 0.3-1.1 mm in diameter, flat to pulvinate, whitish cream to pale reddish brown. Central column whitish to reddish brown, usually darker toward the top; fertile chamber ring-like around the central column; walls and column consisting of pale yellowish brown textura angularis, outer wall and outer layer of the column containing numerous crystals. Phialides (3.7 –)6.3–9.7(– 11.5) × (2 –)2.5–3.8(– 4.7) µm (n = 46), arranged in a palisade on hyaline to yellowish, angular cells, ampulliform to lageniform, less commonly cylindrical. Conidia 1-celled, hyaline, smooth, dimorphic, both morphs formed in the same locule, either ellipsoid to oblong, (6.4 –)7.7–10.2(– 11.7) × (4 –)4.5–5.7(– 6) µm, l/w (1.4 –)1.4–2.2(– 3) (n = 21), with a large guttule and often distinct abscission scar, or cylindrical, (7.7 –)10.2–13.5(– 15.3) × (2.3 –)2.5–3.2(– 3.5) µm, l/w (2.8 –)3.6–4.7(– 5.6) (n = 45), straight or curved, with mostly 3 or 4 confluent guttules.

Culture characteristics.

On CMD at 16 °C in the dark colony more-or-less circular, of loose mycelium, first white, variably covered by white aerial hyphae, becoming dense, forming white and apricot to orange zones, darkening and turning black from the centre, sometimes forming reddish brown dots, spots or tubercles.

Other specimen examined.

Spain, Galicia, Pontevedra, O Grove, 42°28'04"N, 08°53'14"W, on twigs of Castanea sativa , 4 Nov. 2018, M.A. Delgado (WU 37025; culture D303).

Notes.

Dendrostoma atlanticum is easily recognized by its long-pedicellate ascospores having 2-4 large drops, setting it apart from D. castaneum , which has narrow, often curved ascospores with small drops and short appendages. All species described from Castanea in China are only known from asexual morphs ( Jiang et al. 2019).

Figures

Figure 3. Dendrostoma atlanticum. Sexual morph a-d ectostromatic discs and ostioles e pseudostroma in vertical section f pseudostroma in cross section g peridium in cross section (in 3 % KOH) h-k asci l-r ascospores. a-c, f, h, i, k-p WU 37024 = D 196), d, e, g, j, q, r WU 37025 = D 303. Scale bars: 1 mm (f), 500 µm (a-e), 10 µm (g-r).

Figure 4. Dendrostoma atlanticum (WU 37024 = D 196). Asexual morph a, b conidiomata in face view c conidioma in vertical section d vertical section through fertile chamber and part of the central column e, f phialides g-l conidia (cylindrical in g-j, ellipsoid in k, l). d-l In 3 % KOH. Scale bars: 300 µm (a-c), 100 µm (d), 10 µm (e), 5 µm (f-l).