Neochaetothyrina syzygii – Facesoffungi number: FoF 11325

Neochaetothyrina syzygii Crous, sp. nov.

MycoBank number: MB 839532; Index Fungorum number: IF 839532; Facesoffungi number: FoF 11325;

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

Leaf spots absent, saprobic. Ascomata hypophyllous, superficial on leaf tissue, brown, developing beneath a brown mycelial layer, globose, 100 – 200 µm diam, cupulate when dry, surface of brown textura epidermoidea, wall of 2 – 3 layers of brown textura angularis; outer wall of ascomata forming brown, radiating superficial hyphae, branched, septate, anastomosing, with mucoid sheath, constricted at septa, 3 – 6 µm diam; hyphopodia not seen. Setae arising from outer wall of ascoma, dark brown, verruculose to warty, thick-walled, flexuous, 4 –15-septate, tapering to subobtuse apex, 3 – 4 µm diam, up to 300 µm long, 7–10 µm diam at base, at times also arising from superficial mycelium surrounding ascoma, with basal T-cell, slightly swollen. Pseudoparaphyses hyaline, smooth, cellular, constricted at septa, anastomosing, 3 – 4 µm diam. Asci arranged in basal layer, obovoid to broadly ellipsoid, bitunicate, 8-spored, with apical chamber, 5– 6 µm diam, 30– 40 × 20– 25 µm. Ascospores multiseriate, hyaline, smooth, thick-walled, guttulate, granular, fusoid-ellipsoid, straight or curved, apex subobtuse, tapering to obtuse base, constricted at median septum, widest above septum, encased in mucoid sheath, (16 –)17–18(– 22) × (5 –) 6(–7) µm. Ascospores germinating from both ends, becoming brown and verruculose, swollen and distorted, 7– 8 µm diam, but not developing additional septa in ascospore.

Culture characteristics — Colonies erumpent, with sparse aerial mycelium and smooth, lobate margin, reaching 4 mm diam after 2 wk at 25 °C. On MEA, PDA and OA surface and reverse olivaceous grey.

Typus. SOUTH AFRICA, Mpumalanga, Mbombela, Lowveld Botanical Gar- den, on leaves of Syzygium cordatum (Myrtaceae), Nov. 2018, P.W. Crous, HPC 3157 (holotype CBS H-24537, culture ex-type CPC 39051 = CBS 147073, ITS, LSU and rpb2 sequences GenBank MZ064443.1, MZ064500.1 and MZ078207.1).

Notes — When freshly collected leaves colonised by Neochaetothyrina syzygii are incubated in moist chambers, ascomata develop within 1 wk. However, the upper wall is a covering membrane of hyphae, that easily separates during slide preparation, leaving a layer of near naked asci embedded in a brown mucilaginous mass. Neochaetothyrina is reminiscent of Chaetothyrina (Hongsanan et al. 2017), but the latter species lacks superficial hyphae and setae.

Neochaetothyrina syzygii was also compared to Chaetothyrium syzygii (on Syzygium cordatum, Kwazulu-Natal, PREM 33103), but the latter had hyaline, fusoid ascospores that become brown and 3-septate at maturity, 20 × 6 –7 µm. Furthermore, Asterina syzygii (on Syzygium gerrardi, Woodbush, Limpopo Province, PREM 17755) had 1-septate, slightly constricted, brown, finely verruculose ascospores, 27.5 – 35 × 14 –17 µm.

Based on a megablast search of NCBIs GenBank nucleotide database, the closest hits using the ITS sequence had highest similarity to Chaetothyrina guttulata (strain MFLUCC 14-0539, GenBank MN462949.1; Identities = 412/481 (86 %), 23 gaps (4 %)), Xenosonderhenia syzygii (strain MEFC132, GenBank MK732144.1; Identities = 354/399 (89 %), 17 gaps (4 %)) and Pseudosasa guanxianensis (clone 8, GenBank KT006327.1; Identities = 353/399 (88 %), 17 gaps (4 %)). Closest hits using the LSU sequence are Chaetothyrina artocarpi (strain MFLUCC 15-1082, GenBank MF614834.1; Identities = 802/823 (97 %), one gap (0 %)), Chaetothyrina guttulata (strain MFLUCC 14- 0539, GenBank MN462949.1; Identities = 830/852 (97 %), one gap (0 %)) and Houjia yanglingensis (strain CBS 125225, GenBank NG_064220.1; Identities = 835/860 (97 %), one gap (0 %)). Distant hits using the rpb2 sequence had highest similarity to Houjia pomigena (strain CBS 125224, GenBank MF951422.1; Identities = 640/801 (80 %), two gaps (0 %)), Hyalocercosporidium desmodii (strain CBS 142179, GenBank MF951503.1; Identities = 660/880 (75 %), 26 gaps (2 %)) and Stromatoseptoria castaneicola (strain CBS 102322, GenBank MF951681.1; Identities = 665/888 (75 %), 24 gaps (2 %)).