Melanconis marginalis subsp. tirolensis Jaklitsch & Voglmayr, 2020

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

Melanconis marginalis subsp. tirolensis Jaklitsch & Voglmayr subsp. nov. Figures 10 , 11

Diagnosis.

This subspecies differs from Melanconis marginalis subsp. europaea and subsp. marginalis phylogenetically and by slightly larger α-conidia, asci, ascospores and ascospore appendages.

Type material.

Holotype: Austria, Tirol, Osttirol, Prägraten am Großvenediger, Umbalfälle, grid square 8939/4, on Alnus alnobetula , 10 Sep 2001, W. Jaklitsch W.J. 1796 (BPI 872035; ex-type culture CBS 122310 = A.R. 3748 = ME4; part preserved as isotype WU 31892, asexual morph only present in the latter).

Etymology.

Named after its occurrence in Tirol, Austria.

Description.

Sexual morph: Pseudostromata 1.3-5.5 mm diam., conspicuous and numerous, scattered to aggregated, pulvinate, circular to elliptical in outline, elevated beyond bark surface forming pustules; consisting of an ectostromatic disc and perithecia embedded in an entostroma around a central column. Ectostromatic discs 0.35-1.55 mm (n = 43) diam. or long, bright white to yellowish, turning brownish with age, mostly fusoid, also elliptic or circular in outline, mostly flat, crumbly, distinctly projecting up to 1.3 mm, including projecting part of the pseudostroma; central column beneath disc white to yellowish, consisting of hyaline hyphae and colourless crystals. Ostiolar necks cylindrical, laterally or centrally attached on perithecia, convergent in the disc margin or crowded at the ends of fusoid discs, 1-15 per disc. Visible part of the ostiolar necks (53-)85-180(-240) µm (n = 56) diam., black, often with olivaceous tips, frequently conical to bristle-like and projecting to 0.4 mm, but also papillate, resembling minute perithecia or discoid with depressed centre. Entostroma bark coloured, not or only slightly paler than the surrounding bark, consisting of bark cells and some light-coloured hyphae. Perithecia (510-)570-780(-900) µm (n = 36) 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 absent at maturity. Asci floating free at maturity, (74-)86-102(-115) × (11.3-)13-20(-25) µm (n = 61), fusoid to oblong or clavate, short-stipitate prior to full maturation, 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 (15.8-)17.8-21.2(-24) × (4.5-)5.5-7(-8) µm, l/w (2.5-)2.8-3.5(-4) (n = 123), hyaline, turning pale brown with age, oblong to ellipsoid, symmetric to slightly inequilateral with nearly equal cells, slightly or strongly constricted at the median septum, multiguttulate or with 1-2 large and several small guttules when fresh, with a short and broad, rounded, parabolic or vesicular, sometimes tapering but typically terminally broadly truncate appendage (2-)3.8-6.2(-9.5) × (3-)4-5.7(-7.2) µm, l/w (0.4-)0.8-1.4(-2) (n = 104) at each end, after release becoming invisible in 3% KOH, but partly persistent in Congo Red.

Asexual morph acervular, intermingled with pseudostromata of the sexual morph or developing separately, inconspicuous. First white to yellowish tissue (central column) forming within the bark, becoming visible by slightly pustulate bark and narrow whitish to yellowish discs emerging through bark cracks, usually first followed by the production of β-conidia in olivaceous chambers and later α-conidia or both more or less simultaneously on the same or similar conidiophores, chambers fusing into a single locule, turning brown and dark conidial patches 0.5-1.5 mm diam. or perithecia of the sexual morph forming. Conidiomata 1.2-3.2 mm diam., pulvinate, more or less circular in outline, scattered or crowded. Covering discs 0.2-1.5 mm (n = 14) diam. or long, narrowly fusoid or longish to circular, flat to convex, whitish, yellowish to brownish; discs and pulvinate or conical columns beneath consisting of compact textura intricata of hyaline hyphae and numerous colourless crystals, becoming brittle with age. Conidiophores emerging around the central column in dense palisades, up to ca. 65 µm long, filiform, branched near the base and usually 1-3 fold asymmetrically at higher levels, first hyaline, turning brown from their tips; terminal conidiogenous cells (9-)15-25(-28) × (1.7-)2.3-3.2(-3.7) µm (n = 63), cylindrical and often widened towards base, even wider at the funnel-shaped tips, with up to 3 annellations, proliferating and producing α- or β-conidia. Conidia dimorphic, α-conidia (10-)11.5-16.3(-21.8) × (2.5-)4.5-6.3(-7.5) µm, l/w (1.8-)2.1-3.2(-5.3) (n = 70), first hyaline, soon turning light to medium brown, mostly fusoid, also oblong, oval or ellipsoid, straight or slightly curved, upper end usually subacute and sometimes elongated, lower end narrowly truncate, containing several guttules, smooth; β-conidia (7.3-)8.8-12(-16.5) × (2-)2.2-2.7(-3.4) µm, l/w (2.6-)3.3-5.3(-8.9) (n = 104), hyaline, dilute brownish with age, sometimes turning rosy in 3% KOH, oblong to cylindrical, straight or curved or sigmoid, thick-walled in water, smooth, with truncate basal scar and minute guttules to eguttulate.

Culture: Colony on MEA dense, first hyaline to white, with restricted growth, forming brown radial portions mostly submerged in the agar. Odour unpleasant.

Distribution and ecology.

Co-occurring with Melanconis marginalis subsp. europaea in a subalpine area of eastern Tyrol, Austria, Europe, on Alnus alnobetula .

Additional material examined.

Austria, Tirol, Osttirol, Virgental, Prägraten am Großvenediger, Lasörling, Zopatnitzen on path between Wetterkreuz and Berger See, 2100 m a.s.l., on Alnus alnobetula , 26 Oct 2019, H. Voglmayr & C.M. Botoaca (WU 37851; culture D322a (from α-conidia)).

Notes.

As this subspecies differs morphologically only subtly from the other varieties of M. marginalis , we prefer to classify it as a subspecies rather than a separate species. While the ITS sequences of Melanconis marginalis subsp. tirolensis differs from Melanconis marginalis subsp. europaea in only a single base pair, the differences are substantial in all other markers included, particularly tef1 and tub2.

Figures

Figure 10. Melanconis marginalis subsp. tirolensis. Sexual morph a, b pseudostromata with ectostromatic discs c conical ostioles d vertical section showing central column and two perithecia e ectostromatic disc with subglobose ostiolar tips f cross section showing central column, marginal ostioles and upper parts of perithecia g-j asci (compressed in j) k-p ascospores; i, j, o, p in aqueous Congo Red a, c, k-p holotype BPI 872035 b, d-j isotype WU 31892. Scale bars: 500 µm (a, b, d, f), 150 µm (c), 300 µm (e), 10 µm (g-p).

Figure 11. Melanconis marginalis subsp. tirolensis (isotype WU 31892). Asexual morph a, b conidiomata showing covering discs in face view c, d conidiomata in cross section (c with β-conidia d with α-conidia) e conidioma with α-conidia in vertical section f-l conidiophores and conidiogenous cells (k, l producing β-conidia) m-r α-conidia s-y β-conidia f-y in 3 % KOH. Scale bars: 500 µm (a-e), 15 µm (f), 10 µm (g-l), 5 µm (m-y).