Melanconidaceae G. Winter, Rabenh. Krypt.-Fl., Edn 2 (Leipzig) 1.2: 764 (1886)
Index Fungorum number: IF 80988; 36 species.
Saprobic or pathogenic on plants and wood, in terrestrial and aquatic habitats. Sexual morph: Pseudostromata well-developed, obvious, erumpent. Ectostromatic disc surrounded by bark or not, yellowish-white. Ostiolar canal opening around the disc. Ascomata arranged as circles around the ectostromatic disc, oblique or horizontal, globose to subglobose, coriaceous and black with long, periphysate and lateral ostiolar canals. Peridium with outer, thick-walled, brown cells of textura globosa to textura angularis and inner, thick-walled, flat, hyaline cells of textura angularis. Paraphyses wide, hypha-like, deliquescent at maturity. Asci 8-spored, unitunicate, oblong to fusiform, short pedicellate, with distinct, J-, apical ring. Ascospores overlapping uniseriate to biseriate, hyaline, ellipsoid, 1-septate. Asexual morph: Coelomycetous. melanconium-like. Conidiomata acervular, scattered, solitary, superficial, black, coriaceous. Conidiophores branched at the base, septate, Conidiogenous cells annellidic, cylindrical. Conidia hyaline to brown, ellipsoid or subglobose, smooth-walled, thick-walled (adapted from Senanayake et al. 2017a).
Notes – Melanconidaceae includes species with yellowish-white ectostromatic discs, surrounding the ascomata which are arranged in a circle. Most of the family are saprobes and pathogens which cause diseases on economically important trees. Maharachchikumbura et al. (2016b) included 24 genera in the family. Sequence data is available for Dicarpella, Melanconiella, Melanconis, Melanconium, and Prosthecium. Voglmayr & Jaklitsch (2014) synonymized Prosthecium under Stilbospora and included the genus in Stilbosporaceae. Crous et al. (2012d) included more than half of known wuestneia-like species in Harknessia in Harknessiaceae. Morphological and molecular evidence showed that the family was monogeneric represented by Melanconis and its asexual morph Melanconium (Castlebury et al. 2002; Rossman et al. 2007). Melanconium was synonymized under Melanconis by Rossman et al. (2015). Phylogenetic analysis of Senanayake et al. (2017a) showed that Dicarpella and Melanconiella clustered away from the family. As a result, Senanayake et al. (2017a) excluded all the genera listed in Maharachchikumbura et al. (2016b) from Melanconidaceae, except Melanconis.
Ecological and economic significance of Melanconidaceae
Most sexual and asexual morphs of Melanconis cause cankers and shoot blights (Fan et al. 2016, Senanayake et al. 2018) with various disease symptoms (Fan et al. 2016). Melanconis stilbostoma causes birch dieback (Fan et al. 2016) causing branches in the crown to die off. Some taxa produce antifungal compounds. Thermozymocidin (myriocin) and flavovirin were isolated from Melanconis flavovirens (Sailer et al. 1989) and have shown antifungal activity against yeasts and a few filamentous fungi.
Fig 1 – Phylogram generated from maximum likelihood analysis based on combined LSU, and ITS sequence data representing family Melanconidaceae. Related sequences are taken from Fan et al. (2018). Ten strains are included in the combined analyses which comprise 1720 characters (1200 characters for LSU, 520 characters for ITS) after alignment. Gnomonia gnomon (CBS 119.53) is used as the outgroup taxon. For both genes, GTR+G was applied as the evolutionary model. The best RaxML tree with a final likelihood value of – 3656.825130 is presented. The matrix had 164 distinct alignment patterns, with 21.37%undetermined characters or gaps. Estimated base frequencies were as follows: A = 0.264911, C = 0.220911, G = 0.264143, T = 0.250035; substitution rates AC = 1.561251, AG = 2.163552, AT = 2.584612, CG = 0.506469, CT = 4.714002, GT = 1.000000; gamma distribution shape parameter α = 0.808825. Bootstrap values for ML equal to or greater than 75% (first set) and MP equal to or greater than 75% (second set) are given above the nodes. Ex-type strains are in black and the new strain is indicated in yellow.