Melanconis marginalis subsp. europaea Jaklitsch & Voglmayr, 2020

Jaklitsch, Walter M. & Voglmayr, Hermann, 2020, The genus Melanconis (Diaporthales), MycoKeys 63, pp. 69-117 : 69

Melanconis marginalis subsp. europaea Jaklitsch & Voglmayr subsp. nov. Figures 6 , 7

Diagnosis.

This subspecies of Melanconis marginalis occurs in Europe and differs from the American subsp. marginalis phylogenetically and by slightly larger asci, ascospores and ascospore appendages.

Type material.

Holotype. Austria, Steiermark, Judenburg, Pusterwald, Hinterwinkel, grid square 8651/4, on Alnus incana , 11 Jun 2011, H. Voglmayr (WU 31888, culture CBS 131692 = MAI).

Etymology.

For its occurrence in Europe.

Description.

Sexual morph: Pseudostromata 1.5-3.6 mm diam., usually conspicuous and numerous, scattered to tightly aggregated, forming pustules, pulvinate, circular to elliptical in outline, typically elevated beyond bark surface; consisting of an ectostromatic disc and perithecia embedded in an entostroma around a central column. Ectostromatic discs 0.5-2.1 diam. or long, discrete, less commonly confluent, bright white to yellowish, turning brownish with age, variable, fusoid, elliptic or circular in outline, flat, convex, concave, entire or coarsely fissured and crumbly, projecting up to 1 mm including projecting part of the pseudostroma; central column beneath disc whitish to yellowish, consisting of hyaline hyphae and colourless crystals. Ostiolar necks cylindrical, laterally attached on perithecia, centrally attached only on centrally arranged perithecia, convergent in the disc margin or crowded at the ends of fusoid discs, 1-25(-35) per disc. Visible part of the ostiolar necks (53-)103-167(-212) µm (n = 90) diam., black or brown with black tips, usually circular in section, sometimes plane with the disc, but much more frequently papillate and projecting to 250 µm, often resembling minute perithecia with pointed tips or discoid with depressed centre to nearly ring-like, sometimes conical to bristle-like and projecting to 0.4 mm. Entostroma bark coloured, not or only slightly paler than the surrounding bark, consisting of bark cells and some light-coloured hyphae. Perithecia (450-)515-680(-810) µm (n = 58) diam., arranged in valsoid configuration around and below central column, globose to subglobose, collapsing up- or laterally inwards upon drying. Peridium pseudoparenchymatous, consisting of a dark brown small-celled outer and a hyaline to brownish, large-celled inner layer. Hamathecium of broad multiguttulate paraphyses, collapsing, dissolving and usually absent amongst mature asci. Asci floating free at maturity, (52-)68-85(-98) × (8.7-)10.5-15.5(-18.7) µm (n = 126), narrowly fusoid to oblong or narrowly ellipsoid, with an apical ring distinct in water and staining in Congo Red, but invisible or indistinct in 3% KOH, containing 8 biseriate or obliquely uniseriate ascospores. Ascospores (13.8-)17-20(-22.8) × (3.5-)4.7-6.5(-7.7) µm, l/w (2.5-)2.9-3.8(-5.5) (n = 242), hyaline, mostly oblong or narrowly ellipsoid, sometimes broadly ellipsoid upon release, symmetric or inequilateral, bicellular with nearly equal cells, slightly or strongly constricted at the median septum, multiguttulate or with few large and several small guttules when fresh, with a short and broad, rounded, sometimes tapering, angular or bell-shaped and typically terminally truncate appendage (1.8-)2.7-4.7(-8.4) × (2-)2.5-4(-5.5) µm, l/w (0.4-)0.9-1.5(-2.8) (n = 318), at one or both ends becoming invisible in 3% KOH and Congo Red after release.

Asexual morph acervular, intermingled with pseudostromata of the sexual morph or more frequently developing separately, usually inconspicuous, but sometimes becoming conspicuous due to greyish-brown to dark brown conidial deposits 0.2-0.6 mm diam., rarely confluent from 2 conidiomata and then up to more than 1 cm long. First, white to yellow tissue (central column) forming within the bark, becoming visible by pustulate bark and narrow whitish to yellowish or brownish slit-like discs emerging through bark cracks, usually first followed by the production of β-conidia in olivaceous chambers and later α-conidia on the same or similar conidiophores turning the contents brown and oozing out from ends of the discs or perithecia of the sexual morph formed below the acervulus. Conidiomata 1-2 mm diam., pulvinate, more or less circular in outline, scattered or aggregated in lines. Covering discs 0.3-0.9(-1.6) mm (n = 45) long, narrowly fusoid or longish to rounded, plane to convex, becoming covered and obscured by conidial deposits; discs and pulvinate or conical columns beneath, consisting of compact textura intricata of hyaline hyphae and numerous colourless crystals. Conidiophores emerging around the central column or directly on bark in dense palisades, up to ca. 50 µm long, filiform, branched near the base or sometimes 1-2 fold asymmetrically at higher levels, hyaline, turning brown from their tips; terminal conidiogenous cells (10-)14.5-23(-27) × (1.8-)2.3-3.5(-5) µm (n = 90), cylindrical and often widened in the middle or towards base and at the funnel-shaped tips beyond its width, with up to 3 annellations, producing β-conidia and/or α-conidia. Conidia dimorphic, α-conidia (9-)11-14(-16.3) × (3.2-)4.5-5.5(-6.2) µm, l/w (1.7-)2.2-2.9(-3.6) (n = 172), first hyaline, soon turning pale to medium brown or greyish-brown, unicellular, mostly fusoid, but also oblong, oval or ellipsoid, straight, less commonly slightly curved, upper end usually subacute and sometimes elongated, lower end narrowly truncate, containing several guttules, smooth; β- conidia (8-)9-11.5(-12.7) × (2-)2.5-3(-3.3) µm, l/w (2.8-)3.3-4.6(-5.8) (n = 39), hyaline to dilute brownish, unicellular, oblong to cylindrical, straight or slightly curved, thick-walled in water, with few guttules to eguttulate, smooth.

Culture: Colony on CMD at 16 °C first hyaline, partly or entirely turning brownish or ochre, either covered by a dense white mat of aerial hyphae or not, sometimes becoming indistinctly zonate, sometimes forming irregularly disposed conidiomata; on MEA at room temperature, first hyaline to whitish, soon forming a few broad zones with uneven margins forming teeth, the latter partly turning brown.

Distribution and ecology.

Common on Alnus alnobetula (syn. A. viridis ) and A. incana in mountainous areas of Central and Eastern Europe (confirmed for Austria, the Czech Republic fide Podlahová 1973, Romania fide Szász 1966 and Switzerland fide Sieber et al. 1991).

Other material examined.

Austria, Burgenland, Forchtenstein, Kohlstatt, on Alnus incana , 24 Sep 2016, H. Voglmayr & W. Jaklitsch (WU 37046, culture D257); Kärnten, Hüttenberg, Knappenberg, grid square 9053/3, on Alnus alnobetula , 10 Jun 1992, W. Jaklitsch (WU 15093); Niederösterreich, Aspangberg-St. Peter, Mariensee, grid square 8461/4, on Alnus alnobetula , 23 Sep 2009, H. Voglmayr (WU 29888); Steiermark, Hartberg, Pinggau, Schaueregg, Alte Glashütte, on Alnus alnobetula , 28 Jul 2012, W. Jaklitsch & H. Voglmayr (WU 38243); Judenburg, Pusterwald, grid square 8652/3, on Alnus alnobetula , 11 Jun 2011, H. Voglmayr (WU 31890, culture MAV1); Liezen, Kleinsölk, walking path between Breitlahnhütte and Schwarzensee, grid square 8649/3, on Alnus alnobetula , 6 Aug 2003, W. Jaklitsch W.J. 2296 (BPI 843621; culture CBS 121480 = A.R. 4013); St. Nikolai im Sölktal, Sölker Paß, grid square 8750/1, on Alnus alnobetula , 14 Jun 2011, H. Voglmayr (WU 31889, culture CBS 131694 = MAV); Spital am Semmering, near Pfaffensattel, grid square 8460/2, on Alnus alnobetula , 15 Aug 2003, W. Jaklitsch W.J. 2331 (BPI 872072; culture A.R. 4032); ibidem, same host, 8 Jul 2010, I. Krisai-Greilhuber & H. Voglmayr (WU 31172); ibidem, same host, 7 Apr 2015, H. Voglmayr (WU 36699); Tirol, Kühtai, between Haggen and Kühtai, near Zirmbachalm, grid square 8732/3, on Alnus alnobetula , 3 Sep 2003, W Jaklitsch W.J. 2368 (W 2004-0000062); Prägraten, Bodenalm, on Alnus alnobetula , 18 Jun 2015, H. Voglmayr & W. Jaklitsch (WU 37044; culture D157); Umbalfälle, grid square 8939/4, on Alnus alnobetula , 28 Aug 2000, W. Jaklitsch W.J. 1542 (WU 31891, BPI 748444; culture CBS 109773 = A.R. 3500; AFTOL-ID 2127); same area and host, 17 Jun 2015, H. Voglmayr & W. Jaklitsch (WU 37045; culture D158); Vienna, Landstraße, Botanical garden, Alpinum, grid square 7864/1, on Alnus alnobetula , 21 Aug 1994, H. Voglmayr (WU 12976); same place and host, 6 Jan 2012, H. Voglmayr (WU 31893).

Notes.

This subspecies differs mainly in its occurrence in (Central) Europe and by forming a clade of its own in phylogenetic analyses (Fig. 1 ). While the differences of the European accessions in each marker included are few, they are consistent, resulting in a well-delimited clade in the multigene analyses. As the morphological differences from M. marginalis subsp. marginalis are only small, we prefer to classify the European taxon as a subspecies rather than a separate species.

Under the name Melanconis alni , Podlahová (1973) described both sexual and asexual morphs of a Czech collection from Alnus alnobetula which clearly represents M. marginalis , and Szász (1966) listed and described the species (as Melanconium dimorphum ) from Romania, again from Alnus alnobetula . In his isozyme studies of Melanconium , Sieber et al. (1991) included a Swiss isolate from Alnus alnobetula (as Melanconium sp. 1). This isolate showed a distinct but similar isozyme pattern to North American collections of Melanconis marginalis and had a mean conidial size of 11.7 × 4.3 µm, indicating that this isolate also represents Melanconis marginalis subsp. europaea .

Figures

Figure 1. Phylogram of the best ML tree (lnL = - 18240.558) revealed by RAxML from an analysis of the ITS-LSU- ms 204 - rpb 2 - tef 1 - tub 2 matrix of Melanconis, with 5 species of Juglanconis (Juglanconidaceae) selected as outgroup. ML and MP bootstrap support above 50 % are given at the first and second position, respectively, above or below the branches. Strain numbers are given following the taxon names; strains formatted in bold were sequenced in the current study. Melanconis taxa occurring on Alnus are marked blue, those on Betula in green. The broken branches to the outgroup were scaled to 10 %.

Figure 6. Melanconis marginalis subsp. europaea. Sexual morph a pseudostroma in face view b, c ectostromatic discs d subglobose visible part of ostiolar necks e, f cross sections (e showing central column and marginal ostioles f showing central column and perithecia) g vertical section showing central column and two perithecia h-p asci q-y ascospores m-p in aqueous Congo Red a WU 31890 = MAV 1 b-g, j, n, q, s, t, w-y holotype WU 31888 = MAI h, i, m WU 37045 = D 158 k, r WU 36699 l, p WU 31172 o WU 29888 u WU 31889 = MAV v WU 38243. Scale bars: 1 mm (a, f), 500 µm (b, c, e, g), 150 µm (d), 10 µm (h-q, t), 7 µm (r, s, u-y).

Figure 7. Melanconis marginalis subsp. europaea. Asexual morph a, b conidiomata and conidial deposits in face view c conidioma with β-conidia in cross section d conidioma with α-conidia in vertical section e-h conidiophores and conidiogenous cells (producing α-conidia in e, f, β-conidia in g, h) i-p α-conidia q-t β-conidia e-t in 3 % KOH a, b, d-f, i-k, q-s WU 37044 = D 157 c, g, h, l, t WU 31893 m WU 31891 = W. J. 1542 n WU 31888 = MAI o, p WU 31889 = MAV. Scale bars: 500 µm (a-d), 5 µm (e-t).