Melanconis alni Tul. & C. Tul., Select. fung. carpol. (Paris) 2: 122 (1863).

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

Melanconis alni Tul. & C. Tul., Select. fung. carpol. (Paris) 2: 122 (1863). Figures 3 , 4

≡ Melanconis alni Tul., Annls Sci. Nat., Bot., sér. 4, 5: 109 (1856). (Nom. inval., Art. 35.1).

= Rehm, Ascom. exs. 148 (1872).

?= Melanconium apiocarpum Link, in Willdenow, Sp. pl., Edn 4 6(2): 90 (1825).

?= M. sphaeroideum Link, in Willdenow, Sp. pl., Edn 4 6(2): 92 (1825).

?= Stilbospora microsperma Pers., Observ. mycol. (Lipsiae) 1: 31 (1796).

Diagnosis.

Melanconis alni is recognised by ascospores having filiform, tapering appendages and dark brown α-conidia with a pale to subhyaline median area.

Type material.

Lectotype, here designated: France, Hauts-de-Seine, Chaville, on Alnus glutinosa , 1 Feb 1856, Tulasne (PC 0723592; MBT390380). Epitype, here designated: Austria, Oberösterreich, Raab, Wetzlbach, grid square 7648/1, on Alnus glutinosa , 4 Jun 2011, H. Voglmayr (WU 31883; ex-epitype cultures CBS 131695 = MAW (from ascospores), MEW (from α-conidia); MBT390381).

Description.

Sexual morph: Pseudostromata developing in bark after the asexual morph and sometimes with acervuli of the asexual morph still present within their sides, 0.9-2.7 mm diam., scattered, pulvinate, more or less circular in outline, slightly projecting from the bark surface and then causing a greyish bark surface; consisting of an ectostromatic disc and perithecia embedded in an entostroma. Ectostromatic discs 0.3-1.4 mm diam., white to yellowish, brownish when old, flat to convex, circular, fusoid, angular or elongate in section, projecting up to 0.6 mm. Ostiolar necks cylindrical, laterally attached on perithecia and convergent in the disc, centrally only on centrally arranged perithecia, 1-15(-20) per disc, in the disc plane, convex to papillate and slightly projecting, with dark rounded tips; first pale brownish to greyish-brown, turning black, (70-)93-162(-210) µm (n = 33) diam. apically, mostly present at the margins but often also randomly within the disc. Entostroma bark-coloured, not or only slightly paler than the surrounding bark, consisting of bark cells and some light-coloured hyphae. Perithecia (390-)450-645(-765) µm (n = 24) diam., formed below overmature conidiomata in valsoid configuration, globose to subglobose, collapsing up- or laterally inwards upon drying. Hamathecium of wide multiguttulate paraphyses, collapsing, dissolving and usually absent amongst mature asci. Asci floating free at maturity, (68-)79-97(-110) × (10.5-)12.5-16.5(-21) µm (n = 114), narrowly clavate, fusoid, oblong to nearly ellipsoid, with an apical ring staining in Congo Red but invisible or indistinct in the strongly thickened apex in 3% potassium hydroxide (KOH), containing 8 biseriate ascospores. Ascospores (14.5-)16-21(-25.3) × (4.7-)6-7.8(-9) µm, l/w (1.9-)2.3-3.2(-4.8) (n = 198), hyaline, ellipsoid, clavate or inequilaterally fusoid, bicellular with upper cell usually slightly wider, slightly or strongly constricted at the median septum, thick-walled, multiguttulate or with one large and several small guttules when fresh, with a filiform, tapering and acute, less commonly short and stout rounded, triangular or truncate appendage (2.5-)4.7-10(-24.3) × (1.7-)2.3-3(- 4) µm, l/w (1-)1.8-3.8(-8.4) (n = 224) at one or both ends; in 3% KOH, appendages invisible and cells tending to be more equal.

Asexual morph acervular, often conspicuous due to thick black conidial masses, first subperidermal, after ejection forming deposits 0.5-3.6 mm diam., sometimes confluent from 2-3 conidiomata and then up to 5 mm long, projecting to 0.5 mm. Conidiomata scattered, gregarious, sometimes confluent, pulvinate to conical, (0.6-) 0.8-2.5 mm diam., consisting of a superficial, ca. 0.2-1.3 mm wide, flat, white to yellowish, slightly projecting disc becoming concealed by dark brown to black conidial deposits, a whitish to yellowish, when old orange-brown, compact, more or less pseudoparenchymatous base, in the centre arising as central column with circular to longish outline and sometimes wavy margin, surrounded by conidiophores and black conidial chambers. Conidiophores emerging radially from the pseudoparenchymatous base and column surface, filiform, to ca. 50 × 4 µm, branching 1-3 times from their bases producing whorls of conidiogenous cells. Conidiogenous cells (10-)12-43 × 2-4 µm, annellidic, more or less cylindrical, hyaline, turning brown with age, forming more or less simultaneously two types of conidia on top. Conidia dimorphic, α- conidia (9-)10.5-12.2(-14) × (4.8-) 6.8-8(-9) µm, l/w (1.2-)1.4-1.7(-2.4) (n = 301), dark brown, more or less cuboid or subglobose and often with pinched sides or oval, oblong to broadly ellipsoid, with a diffuse or more or less well-defined, paler to subhyaline median area or stripe; β-conidia produced in small numbers, (5.3-)7.3-10.3(-11.5) × (2-)2.5-3.2(-3.7) µm, l/w (2-)2.6-3.9(-4.7) (n = 38), oblong, mostly straight, hyaline to subhyaline, turning dilute brownish with age, containing few minute guttules, with a distinct basal abscission scar.

Culture: Colony on CMD at 16 °C first hyaline, turning yellowish-brown from the centre, becoming covered by flocks of white aerial hyphae and conidiomata forming around the centre or colony irregular, with limited growth, turning green to black due to conidiomata; on MEA first hyaline, circular, with short aerial hyphae, forming concentric zones, the outer white, the inner turning brown, black conidiomata forming between the zones, margin becoming diffuse and the entire colony turning brown. Odour indistinct.

Distribution and ecology.

Melanconis alni occurs in Europe on dead twigs and branches of Alnus glutinosa and A. incana , mainly at lower elevations.

Additional material examined.

Austria, Kärnten, Eisenkappel, Bad Vellach, Vellacher Kotschna, grid square 9653/1, on Alnus incana , 7 Sep 1998, W. Jaklitsch W.J. 1194 (WU 31887); St. Margareten im Rosental, village area, at the brook Tumpfi, grid square 9452/4, on Alnus glutinosa , 18 Jul 1994, W. Jaklitsch W.J. 148 (WU 31885); Trieblach, Drau-Auen, near Kucher, grid square 9452/2, on Alnus incana , 7 Aug 1994, W. Jaklitsch W.J. 178 (WU 31886); Niederösterreich, Michelbach, Mayerhöfen, on Alnus glutinosa , 18 Jun 2011, H. Voglmayr (WU 31882, culture CBS 131693 = MAMI). FRANCE, Alpes-de-Haute-Provence, Trigance SE Castellane, at the river Jabron ca. 500 m elev. before entering the Verdon river, on Alnus incana , 4 Aug 2011, H. Voglmayr (WU 31884; culture MAIV); Ariége-Rimont, Peyrau, on Alnus glutinosa , soc. Diplodia sp., 26 Jul 2010, J. Fournier J.F. 10104 (WU 37043); Hauts-de-Seine, Chaville, on Alnus glutinosa , 11 Oct 1852, Tulasne (PC 0723589, PC 0723596); Meudon, on Alnus glutinosa , 13 May 1856, Tulasne (PC 0723593); Oise, Pierrefonds, on Alnus glutinosa , 30 Jul 1857, Tulasne (PC 0723590, PC 0723591); Yvelines, Viroflay, on Alnus glutinosa , July 1860, Tulasne (PC 0723594, PC 0723595); no collection data, Tulasne (PC 0723588). POLAND, S Kuligi, Biebrzański Park Narodowy, on Alnus glutinosa , 28 Jul 2015, H. Voglmayr (WU 37042, culture D156).

Notes.

Melanconis alni was described by Tulasne from Alnus glutinosa in 1856 after a presentation of the topic in April 1856. Tulasne and Tulasne (1863) validated the name in Melanconis , illustrated ascospores with typical long acute appendages and mentioned material from Meudon and Chaville. In PC, nine specimens of Tulasne are extant in the Melanconis alni folder; three of them were collected after its description in 1856 and, for one, no collection data are available. PC 0723590, PC 0723591, PC 0723593, PC 0723594 and PC 0723595 were collected after the publication date. PC 0723588 (no data) and PC 0723589, PC 0723596 from 1852 only contain asexual morph, but in the protologue, the sexual morph is also described. Therefore, we select PC 0723592, which also contains few pseudostromata of the sexual morph, as the lectotype. In PC 0723592 and PC 0723595, both α- and β-conidia are present. Generally, β-conidia are inconspicuous and produced in small numbers, i.e. they are easily overlooked. Asci in old herbarium material are shrunk and difficult to rehydrate, therefore significantly smaller than those of fresh material. In KOH, the ascus apex becomes very thick and the ring disappears; also ascospore appendages disappear in KOH.

Tulasne and Tulasne (1863) and Wehmeyer (1941) listed the following asexual morph names, amongst others, as linked to M. alni : Stilbospora microsperma Pers. Material with this name is not accessible in L; Melanconium sphaeroideum Link (1825) is more generally given as the name of the asexual morph. Sieber et al. (1991) used another name described by Link (1825), Melanconium apiocarpum , for the asexual morph of Melanconis alni . As Link´s type material of these taxa is not extant in B, we are unable to draw a conclusion about their identity; in addition, the descriptions in Link (1825) are vague and he gave no hosts. Therefore, we continue to use the name M. alni , which is generally well-known. Type material of Melanconium atrum Link, the generic type of Melanconium , described from Germany (K(M) 171588, slide from Melanconium atrum type material from Persoon´s herbarium) has conidia of the same shape, size and lighter median band (Fig. 4p ) and may thus be conspecific with M. alni , but it was described from Fagus sylvatica . According to Sutton (1964), Link had sent his material to Persoon, because in the herbarium of the latter 3 specimens labelled M. atrum were extant. The host of one of these materials was identified as Fagus , based on bark structure. This specimen was selected as lectotype. The slide K(M) 171588 (= IMI 102914) was prepared from the lectotype and is thus an isotype. Accordingly, Melanconium atrum is a different species, despite its morphological similarity with M. alni , because the latter only occurs on Alnus spp. We have not seen any Melanconium on Fagus , but Petrini and Fisher (1988), Sieber et al. (1991) and Kowalski and Kehr (1992) reported and isolated M. atrum as an endophyte of Fagus . For α-conidia of isolates from Fagus sylvatica and Quercus robur , Sieber et al. (1991) reported mean sizes of 11.7-12 × 8.5-8.9 µm, which were similar to those from Alnus glutinosa (on average, 10.1-12.3 × 5.9-7.4 µm). However, the protein profiles revealed by isozyme electrophoresis differed markedly between the isolates from Alnus glutinosa and those from Fagus / Quercus , confirming them to represent distinct species that may not even be congeneric. Another fact may support the presence of morphologically similar but rare taxa on Fagaceae , as, for example, Melanconium gourdaeforme with similar conidia was described by Kobayashi (1968) from Castanea . A narrow light band is also characteristic for conidia of Melanconiella ostryae ( Voglmayr et al. 2012).

Ascospore appendages of Melanconis alni may sometimes be similar to those of M. marginalis , at least in fractions, although truncate appendages in M. alni are rather a consequence of microscopic mount preparation. On Alnus incana both species occur, therefore the asexual morph should be sought for to reliably identify the species.

Figures

Figure 3. Melanconis alni. Sexual morph a, b ectostromatic discs c pseudostroma with ectostromatic disc in face view d cross section showing remnants of asexual morph at the sides of the sexual pseudostroma e cross section showing perithecia with lateral ostiolar necks and central column f vertical section showing perithecium with central ostiolar neck g-j asci k, l ascus apices showing apical ring m-x ascospores j, l, w in aqueous Congo Red a, b, i WU 31885 = W. J. 148 c-f, j, o-q epitype WU 31884 = MAIV g, h, k, l, x WU 37043 = J. F. 10104 m lectotype PC 0723592 n WU 37042 = D 156 r, s WU 31882 = MAMI t, u WU 31883 = MAW v WU 31887 = W. J. 1194 w WU 31886 = W. J. 178. Scale bars: 400 µm (a, b, d-f), 500 µm (c), 10 µm (g-j, n, s-u), 7 µm (k-m, o-r, v-x).

Figure 4. Melanconis alni. Asexual morph a, b conidiomata in face view c conidioma in cross section d conidioma in vertical section e-i conidiophores and conidiogenous cells j-p α-conidia q-t β-conidia a, f WU 31885 = W. J. 148 b-d, h, m, q, s epitype WU 31884 = MAIV e, i PC 0723596 g, j, k lectotype PC 0723592 l, r WU 37043 = J. F. 10104 n, t PC 0723595 o WU 31886 = W. J. 178 p M. atrum isotype K (M) 171588 e-o, q-t in 3 % KOH. Scale bars: 300 µm (a-d), 10 µm (e), 7 µm (f-i), 5 µm (j-t).