Nigrograna neriicola Y. H. Lu, H. Z. Du & Jian K. Liu sp. nov.

Fig. 8

Etymology.

The epithet ‘ neriicola ’ refers to the host genus Nerium from which the fungus was originally isolated.

Holotype.

HKAS 131313.

Description.

Saprobic on dead branches of Nerium oleander (Apocynaceae). Sexual morph: Ascomata 138–231 μm wide, 156–251 μm high (x ̅ = 182 × 202 μm, n = 20), mostly gregarious, sometimes solitary, scattered, immersed to semi-immersed, appearing as black irregular protrusions and cracks, globose to subglobose, sometimes obpyriform, dark brown to black, with an ostiole. Ostioles 32–54 μm long, 14–34 μm wide (x ̅ = 45 × 25 μm, n = 20) mostly central, some eccentric, with a crest-like apex. Peridium 16–61 μm (x ̅ = 32 μm, n = 20) wide, multi-layered, reticulate structure, comprising dark brown to reddish brown pigmented cells of textura angularis. Hamathecium 1–2.5 μm wide (x ̅ = 2 μm, n = 20), composed of numerous, filiform, hyaline, aseptate or separate, rarely branched, filamentous, smooth-walled pseudoparaphyses. Asci 35–80 × 7–10 μm (x ̅ = 56 × 8.5 μm, n = 30), 8 - spored, bitunicate, fissitunicate, clavate to cylindric-clavate, short stalked, some with club-shape pedicel, apically rounded with a small ocular chamber. Ascospores 12–21 (– 31) × 3.5–5 μm (x ̅ = 16 × 4 μm, n = 50), uni- to bi-seriately arranged, partially overlapping, fusoid to ellipsoid, tapering towards the blunt ends, or blunt at both ends, straight or slightly curved, guttulate, smooth-walled, 1 - septate, subhyaline to slightly brown when young; becoming 3 - septate, yellowish-brown to dark brown when mature, deeply constricted at septa, without appendages. Asexual morph: Undetermined.

Culture characteristics.

Ascospores germinated on PDA within 24 h, and germ tubes produced from basal cell. Colonies growing on PDA reached 33–35 mm in diameter after one month at 25 ° C in dark, slightly brown in the whole colony and raised in the central point from above, circular, edge entire, margin well-defined, aerial mycelia dense; in reverse, black-brown in the center, slightly brown ring at the margin, no pigmentation on PDA.

Material examined.

China • Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Mengla County, Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences. 21°55'52′′N, 101°15'29′′E, elevation 505 m, on dead branches of medicinal plant Nerium oleander L. (Apocynaceae), 10 November 2022, H. Z. Du, D 04 (HKAS 131313, holotype); ex-holotype living culture CGMCC 3.25624; • ibid., Sichuan Province, Chengdu City, Pujiang County. 30°11'40"N, 103°22'25"E, elevation 600 m, on dead branches of Camellia sinensis (L.) O. Ktze. (Theaceae), 5 October 2022, Y. H. Lu & Y. Xiao, M 03 (HUEST 23.0195, paratype); ex-paratype living culture UESTCC 23.0195.

Notes.

Nigrograna neriicola (CGMCC 3.25624 and UESTCC 23.0195) has close phylogenetic relationships with N. schinifolii (GMB 0498 and GMB 0504) but formed a distinct lineage (Fig. 1). Morphologically, the ascomata of N. neriicola differs from N. schinifolii in having black irregular protrusions and cracks, mostly gregarious, and ascospores that are slightly larger than N. schinifolii (12–21 × 3.5–5 μm vs. 10–14 × 2.8–4 μm) (Hu et al. 2023). Additionally, the nucleotide base pair comparison between N. neriicola (ex-type strain, CGMCC 3.25624) and N. schinifolii (ex-type strain, GMB 0498) revealed no significant differences by 375 / 377 bp (99.5 %, 1 gap) of ITS and 507 / 511 bp (99.2 %, without gaps) of tef 1 - α. However, for tef 1 - α gene, the length of the two N. schinifolii strains (GMB 0498 and GMB 0504) is only 511 bp. The problem of low similarity occurred after the blastn search without a corresponding sequence in the same genus for alignment. Therefore, N. neriicola is introduced as a new species with the morpho-molecular data analysis.