Gobabebomyces vachelliae Crous, sp. nov.

MycoBank number: MB 837822; Index Fungorum number: IF 837822; Facesoffungi number: FoF 12081;

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

Conidiomata restricted to thorns, erumpent, pycnidial, opening via irregular rupture of epidermis, brown, subglobose, some- what flattened, 80 –150 µm diam, exuding a brown conidial mass; wall of 3 – 4 layers of brown textura angularis. Conidiophores reduced to conidiogenous cells lining inner cavity, hyaline, smooth, ampulliform to doliiform, phialidic, 3 – 5 × 3–4 µm. Conidia solitary, medium brown, verruculose, aseptate, ellipsoid, thick-walled with obtuse ends, (8 –)10 –11(–12) × (5 –)6(–7) µm. In culture hyphae hyaline to brown, 4 – 6 µm diam, encased in mucoid sheath, constricted at septa, forming hyaline, smooth, aseptate ellipsoid conidia with obtuse ends, 5 –7 × 3 – 4 µm, becoming brown and verruculose, swelling and larger in size, and undergoing microcyclic conidiation.

Culture characteristics — Colonies erumpent, spreading, surface irregular to folded, with sparse aerial mycelium and uneven margin, reaching 10 mm diam after 2 wk at 25 °C. On MEA, PDA and OA surface olivaceous grey, reverse iron-grey.

Typus. NAMIBIA, Gobabeb-Namib Research Institute, on leaves of Vachellia (= Acacia) erioloba (Fabaceae), 19 Nov. 2019, P.W. Crous, HPC 3132 (holotype CBS H-24450, culture ex-type CPC 38885 = CBS 146779, ITS and LSU sequences GenBank MW175335.1 and MW175375.1).

Notes — Gobabebomyces is an asexual, coniothyrium-like coelomycetous morph related to Lembosiniella, a genus of ascomycetes forming dark brown to black, superficial, irregular leaf spots with linear to Y-shaped hysterothecia on Eucalyptus spp. in Australia (Crous et al. 2019b). Species of Lembosiniella are sterile in culture.

Based on a megablast search of NCBIs GenBank nucleotide database, the closest hits using the ITS sequence had highest similarity to Elsinoe phaseoli (strain CBS 165.31, GenBank MH855166.1; Identities = 388/452 (86 %), 30 gaps (6 %)), Lembosiniella eucalyptorum (strain CBS 144603, GenBank NR_165601.1; Identities = 379/443 (86 %), 24 gaps (5 %)), and Elsinoe australis (strain KNa-5, GenBank FJ010328.2; Identities = 384/451 (85 %), 24 gaps (5 %)). Closest hits using the LSU sequence are Endosporium populi-tremuloides (strain UAMH 10529, GenBank NG_064317.1; Identities = 778/816 (95 %), nine gaps (1 %)), Lembosiniella eucalyptorum (strain CBS 144603, GenBank NG_067908.1; Identities = 774/814 (95 %), six gaps (0 %)), and Elsinoe banksiigena (strain CPC 32402, GenBank NG_064552.1; Identities = 772 /814 (95 %), five gaps (0 %)).