Paramicrothecium sambuci Crous, Krimhilde Müller, Siepe, Reul & Osieck, sp. nov.

Index Fungorum number: MB 841832; Facesoffungi number: FoF

Etymology. Name refers to the host genus Sambucus from which it was isolated.

Ascomata superficial to immersed in epidermis, globose, 200 – 350 μm diam, scattered, solitary, hyaline, becoming darker brown (due to maturing ascospores); wall translucent, of textura epidermoidea on surface, wall 10 –15 μm diam, of 3 – 6 layers of textura prismatica in section, wall covered with short, stubby, thick-walled setae, hyaline, ends obtuse, surface warty, 30 –100 × 3 – 4 μm; ascomata initially cleistothecial, but once mature, opening via slightly papillate apex with central ostiole, and ex- uding a black cirrhus of ascospores. Asci unitunicate, clavate to subcylindrical with a long stipe, (25 –)30 – 35 × (7–)8 –10 μm, (2 –)4(– 6)-spored, not staining in Melzer’s reagent. Ascospores ellipsoid, medium brown, becoming dark brown, smooth- and thick-walled, with 2– 3 large guttules, and a large refractive germ pore at each polar end, somewhat truncate, (5 –)7– 9(–10) × (3.5 –)5 – 6(–7.5) μm. Mycelium consisting of hyaline, smooth- walled, branched, septate, 3 – 4 μm diam hyphae. Conidio­ phores reduced to conidiogenous cells that occur singly or more commonly in clusters. Conidiogenous cells hyaline, smooth-walled, arising from superficial mycelium, ampulliform, 7–18 × 4 – 6 μm, consisting of an obovoid venter, 4 –10 μm long, and cylindrical neck, 3 –7 μm long, not flared, 2 – 2.5 μm diam. Conidia hyaline, smooth- and thin-walled, guttulate, aseptate, shortly clavate, apex obtuse, tapering to truncate hilum, 1– 2 μm diam, produced in short, false chains that slime down into a globoid mass, (3 –)3.5 – 4(– 5) × (2 –)2.5(– 3) μm.

Culture characteristics — Colonies erumpent, spreading, with abundant aerial mycelium on MEA, moderate aerial my- celium on PDA, and sparse aerial mycelium on OA, with even, lobate margins, reaching 30 mm diam after 2 wk at 25 °C. On MEA surface dirty white, reverse ochreous; on PDA surface and reverse pale luteous; on OA surface dirty white.

Typus. GERMANY, Bayern, Markredwitz (east of Bayreuth, Bayern), 600 m a.s.l., N50°00’23.9″ E12°06’07.7″, on dead stem base of Sambucus nigra (Adoxaceae), 5 Dec. 2020, M. Reul, HPC 3546 = #8494 (holotype CBS H-24845 culture ex-type CPC 40384 = CBS 148306, ITS, LSU, rpb2 and tub2 sequences GenBank OK664749.1, OK663788.1, OK651179.1 and OK651217.1).

Additional material examined. GERMANY, Nordrhein-Westfalen, Duisburg, Ruhrdeich, near Werthacker (NRW), 35 m a.s.l., N51°26’53.68″ E6°48’04.4″, on dead stem of Sambucus ebulus, 1 Dec. 2020, K. Müller, HPC 3545 = # SI 09/2020. – NETHERLANDS, Utrecht Province, Raaphof, near Bunnik, 2 m a.s.l., N52°03’06” E5°12’41”, on dead stem of Arctium, 24 June 2015, E.R. Osieck, (coll. #3203-9i).

NotesParamicrothecium is phylogenetically closely related but distinct from Pseudomicrothecium (non-ostiolate ascomata, 2-spored asci, smooth-walled ascospores with an indistinct germ pore at each end), and Microthecium (ascomata ostiolate or not asetose (i.e., glabrous or surrounded by hyphae- like hairs sensu Marin-Felix et al. (2018), asci 8-spored, smooth to wrinkled, with germ pores at each end, and phialidic asexual morph) (Marin-Felix et al. 2018).

Based on a megablast search of NCBIs GenBank nucleotide database, the closest hits using the ITS sequence had highest similarity to Thielavia basicola (strain CBS 178.82, GenBank NR_165582.1; Identities = 490/544 (90 %), 25 gaps (4 %)), Micro­ thecium quadrangulatum (strain Y-049, GenBank MN562054.1; Identities = 387/439 (88 %), 18 gaps (4 %)), and Microthecium zobelii (strain CBS 341.73, GenBank MK926782.1; Identities = 387/439 (88 %), 18 gaps (4 %)). Closest hits using the LSU sequence are Thielavia basicola (strain CBS 178.82, GenBank MK926783.1; Identities = 515 /526 (98 %), no gaps), Melano­ spora subterranea (= Pseudomicrothecium subterraneum) (voucher BJTC FAN1001, GenBank NG_060274.1; Identities = 808/830 (97 %), three gaps (0 %)), and Melanospora subterra­ nea (voucher BJTC fan1001, GenBank JN247804.1; Identities = 808/830 (97 %), three gaps (0 %)). The best hit using the rpb2 sequence had highest similarity to Thielavia basicola (strain CBS 178.82, GenBank MK876745.1; Identities = 728 /838 (87 %), no gaps). No significant hits were obtained when the tub2 sequence was used in blastn and megablast searches.