Melanconis larissae Jaklitsch & Voglmayr, 2020

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

Melanconis larissae Jaklitsch & Voglmayr sp. nov. Figure 5

Diagnosis.

Melanconis larissae differs from M. stilbostoma by α-conidia having a broad diffuse light-coloured zone.

Type material.

Holotype. USA, New York, Adirondack Mts., Cranberry Lake, on Betula sp., 13 Jun 2002, L. Vasilyeva (BPI 870998; ex-type culture CBS 123196 = A.R. 3886, ME7).

Etymology.

Named after the collector Larissa Vasilyeva.

Description.

Sexual morph: Pseudostromata 1.8-2.7 mm diam., scattered to aggregated, not or only scarcely projecting from the bark surface, pulvinate, circular to elliptical in outline; consisting of an ectostromatic disc and perithecia embedded in an entostroma around a central column and sometimes conidial locules present on the ostiolar level. Ectostromatic discs 0.5-1.4 mm diam. or long, slightly projecting, fusoid to circular, flat or concave, white to yellow, often concealed by ostioles; central column beneath disc brightly white at upper levels, yellow amongst ostiolar necks at lower levels, consisting of hyaline hyphae and colourless crystals. Ostiolar necks cylindrical, laterally or centrally attached on perithecia, convergent and irregularly inserted in the disc; visible part (88-)130-204(-230) µm (n = 32) diam., 1-12 per disc, black, subglobose to subconical with flat or pointed tips, projecting to 200 µm. Entostroma consisting of hyaline hyphae and bark cells. Perithecia (420-)490-650(-690) µm (n = 14) 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, (69-)84-106(-117) × (11-)13-17.5(-19.7) µm (n = 22), fusoid to oblong, with an apical ring distinct in water and staining in Congo Red, but invisible or indistinct in 3% KOH, containing (2-)4-8 ascospores in biseriate or obliquely uniseriate arrangement. Ascospores (14.8-)17-21.5(-25) × (5.8-)6.5-8.3(-9.7) µm, l/w (1.9-)2.3-3(-3.7) (n = 93), ellipsoid to subfusoid, symmetric or inequilateral, bicellular, hyaline, dilute brownish when old, slightly constricted at the central to slightly eccentric septum, thick-walled, becoming verruculose with age, devoid of appendages.

Asexual morph acervular, intermingled with pseudostromata of the sexual morph or developing separately, conspicuous. First white tissue (central column) forming within the bark, becoming surrounded by a yellow margin and narrow whitish to yellowish discs emerging through bark cracks, followed by the production of conidia in olivaceous to dark brown chambers. Conidiomata 1.3-2.7 mm diam., pulvinate, more or less circular in outline, scattered or crowded. Covering discs 0.25-1.2 mm long, narrowly fusoid or longish to circular, flat to convex, whitish to yellowish, becoming obscured by large, coppery to olivaceous brown conidial deposits 1-4 mm diam., projecting to 1.2 mm, also confluent from two or several conidiomata; discs and pulvinate or conical columns beneath consisting of textura intricata of hyaline hyphae and numerous colourless crystals, becoming brittle with age. Conidiophores emerging around the central column from a pseudoparenchymatous base, ca. 40-70 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 (10.5-)14.5-28(-36.5) × (1.7-)2.5-3.5(-4.2) µm (n = 70), cylindrical and often widened towards base, with funnel-shaped collarette and up to 5 or 6 annellations, densely arranged, repetitive, producing α-conidia. Conidia (9.7-)11-13(-14.5) × (6.5-)7.7-9(-9.5) µm, l/w (1.1-)1.3-1.6(-2.2) (n = 66), oval, subglobose to drop-like, unicellular, dark brown, thick-walled, with a broad lighter coloured median zone and a small scar, smooth. No β-conidia detected.

Culture: Colony on MEA at room temperature circular, dense, first hyaline, turning rosy. Odour indistinct to musty.

Distribution and ecology.

Melanconis larissae is known from a single specimen collected in New York State from an unidentified species of Betula .

Notes.

The description of this taxon is based on a single specimen with over-mature sexual morph and well-developed asexual morph with thick masses of conidia. Melanconis larissae differs from M. stilbostoma by the broad light-coloured zone of its conidia. No β-conidia have been detected in this specimen, but oblong to ellipsoid, hyaline to dilute brownish conidia 5-9 × 1.7-5 µm, which we interpret as immature α-conidia.

Figures

Figure 5. Melanconis larissae holotype (BPI 870998) a-o sexual morph a, b ectostromatic discs c, d cross sections showing white upper and yellow lower parts of central columns, ostiolar necks and perithecia e-g asci h-o ascospores f, g in aqueous Congo Red p-y asexual morph p conidial deposit q conidioma in cross section r, s conidiophores and conidiogenous cells (showing annellations in s) t-y α-conidia r-y in 3 % KOH. Scale bars: 500 µm (a-d, p, q), 15 µm (e-g), 7 µm (h-o, r), 5 µm (s-y).