Dendrostoma istriacum Voglmayr & Jaklitsch

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

Dendrostoma istriacum Voglmayr & Jaklitsch sp. nov. Figure 8

Diagnosis.

Dendrostoma istriacum is recognized by narrow, oblong ascospores with small drops.

Holotype.

CROATIA, Istria, Rovinj, near Kamp Amarin, 45°06'33"N, 13°37'02"E, on twigs of Quercus ilex , soc. Diplodia sp., 14 May 2015, H. Voglmayr (WU 37032; ex-type culture CBS 145801 = D122).

Etymology.

Istriacum , referring to its occurrence, Istria.

Description.

Sexual morph: pseudostromata 0.6-1.5 mm in their widest dimension in cross section, pulvinate, circular or elliptic in outline, scattered or tightly aggregated in large numbers, causing bumps in the bark and bark lesions to ca 3.2 mm long parallel to the twig axis. Ectostromatic discs 0.15-0.7 mm in diameter, mostly inconspicuous, surrounded by bark flaps, flat or convex, prosenchymatous, first whitish, turning pale to dark brown, becoming disintegrated and replaced by black ostioles and perithecial tops. Entostroma whitish to pale bark coloured. Stromatic tissues consisting of bark cells and 2-4 µm wide, hyaline to brown hyphae. Ostioles 1-5 per disc, (45 –)61–91(– 103) µm (n = 30) in diameter, short cylindrical, slightly projecting from the disc, brown to black; wall consisting of dark brown textura angularis. Perithecia (230 –)280–393(– 443) µm (n = 20) in diameter, globose to subglobose; peridium ca 15-35 µm thick, pale olivaceous to dark brown, consisting of 2-4 cell layers of thick-walled, dark brown angular cells (3 –)4–13.5(– 20.5) µm (n = 40) in diameter outside and long compressed, thin-walled, hyaline to brownish cells inside. Paraphyses absent at maturity. Asci (59 –)62–70(– 74) × (7 –)8.5–10(– 11) µm (n = 30), fusoid to narrowly clavate, floating freely in the centre, containing 8 bi- to triseriate ascospores. Ascospores (19.3 –)20.5–25.5(– 29.5) × (3 –)3.5–4.2(– 5.1) µm, l/w (4.5 –)5.3–7(– 8.7) (n = 40), 2-celled, constricted at the more-or-less median septum, oblong, straight to curved, with the upper cell often slightly wider than the lower, hyaline, containing several small guttules concentrated towards the ends and the septum, smooth, with a hyaline subconical appendage (1.7 –)2.5–3.5(– 4.5) × (0.8 –)1–1.3(– 1.5) µm (n = 40) at each end, becoming elongated in mounts.

Asexual morph: conidiomata ca 250-520 µm in diameter, acervular, inconspicuous, immersed in bark, causing small bark bumps, becoming visible in fissures, whitish to brownish, flat or convex, bluntly conical, usually broader than high, consisting of a broad sterile greyish brown central column, a white outer fertile ring and a brown covering layer; also fertile between the latter and the top of the column. Covering layer consisting of a dark brown textura angularis of 4-10 µm wide cells, turning paler to hyaline and more rounded downwards; column comprising pale brown textura angularis - epidermoidea of similarly sized cells; outer margin of the fertile ring consisting of a narrow layer of hyaline to pale brown, angular to compressed cells; gel surrounding rounded to angular, subhyaline to hyaline cells supporting phialides slowly turning pinkish in 3% KOH. Phialides forming palisades in fertile areas, tightly packed, cylindrical to ampulliform, often with long acute necks, (5.5 –)6.3–9(– 11) × (1.8 –)2.2–3.7(– 5.3) µm (n = 33). Conidia (4 –)5–6.6(– 7.4) × (1.9 –)2.1–2.5(– 2.7) µm, l/w (1.6 –)2.1–3(– 3.7) (n = 53), oblong to ellipsoid, 1-celled, hyaline, smooth, usually with distinct abscission scar.

Culture characteristics.

On CMD at 16 °C in the dark, colony circular to irregular, dense, white, partly covered by short white aerial hyphae, zonate, soon turning dark brown to black with pale apricot to reddish brown spots and margin and some pale apricot pigment diffusing into agar, reverse dark brown with pale apricot margin.

Other specimen examined.

CROATIA, Istria, Rovinj, near Kamp Veštar, 45°03'19"N, 13°40'55"E, on twigs of Quercus ilex , 30 May 2019, H. Voglmayr (WU 37033).

Notes.

Dendrostoma istriacum is closely related to D. creticum but differs from that species by distinctly shorter ascospores and a different host species.

Figures

Figure 8. Dendrostoma istriacum (WU 37032 = D 122). a-y Sexual morph a-c ectostromatic discs and ostioles d pseudostroma in cross section e peridium in cross section f-j, o-y ascospores k-n asci z-h 1 asexual morph z conidioma in vertical section a 1 upper part of conidioma showing covering layer, upper part of central column and fertile layers with opening at the upper right side b 1 peripheral fertile chamber in vertical section c 1 conidia attached to phialides d 1 - e 1 phialides f 1 - h 1 conidia; e, c 1 - h 1 In 3 % KOH. Scale bars: 150 µm (a-c, z), 300 µm (d), 100 µm (b 1), 50 µm (a 1), 10 µm (e-y, c 1 - e 1), 5 µm (f 1 - h 1).