Nigrograna neriicola Y. H. Lu, H. Z. Du & Jian K. Liu, 2024

Du, Hong-Zhi, Lu, Yu-Hang, Cheewangkoon, Ratchadawan & Liu, Jian-Kui, 2024, Morpho-phylogenetic evidence reveals novel species and new records of Nigrograna (Nigrogranaceae) associated with medicinal plants in Southwestern China, MycoKeys 110, pp. 1-33 : 1-33

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.

Figures

Figure 1. Phylogenetic tree constructed from maximum likelihood (RAxML) analyses of a combined ITS, LSU, rpb 2, SSU, and tef 1 - α sequence data for selected genera within the family Nigrogranaceae (Pleosporales, Dothideomycetes). Branches support for Maximum likelihood (MLBS) equal to or greater than 75 % and Bayesian inference posterior probabilities (BIPP) equal to or greater than 0.95 are marked above or below nodes as MLBS / BIPP. The abbreviation T indicates the ex-type strain. Species names and culture collections in red are newly collected taxa and synonymized isolates. The tree was rooted with Occultibambusa pustula (MFLUCC 11-0502) and O. bambusae (MFLUCC 13-0855).

Figure 8. Nigrograna neriicola (HKAS 131313, holotype) a host Nerium oleander b branch of Nerium oleander c – f appearance of ascomata on host surface g, h vertical section through ascoma i peridium j – n asci o – v ascospores w germinated ascospore x hamathecium y, z colony on PDA, above (y) and below (z). Scale bars: 200 µm (g, h); 100 µm (i); 20 µm (j – n, x); 5 µm (o – v); 10 µm (w).