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

Fig. 9

Etymology.

The epithet ‘ guttulata ’ refers to the guttulate ascospores.

Holotype.

HKAS 131992 .

Description.

Saprobic on dead branches of Camellia sinensis ( Theaceae ). Sexual morph: Ascomata 182–283 μm wide, 106–276 μm high (x ̅ = 241 × 183 μm, n = 20), solitary, immersed, ostiolar necks visible on the host surface or erumpent, triangular, globose to subglobose, sometimes obpyriform, coriaceous, ostiolate, dark brown to black. Ostioles 35–61 μm long, 15–30 μm wide (x ̅ = 47 × 22 μm, n = 20) mostly central, some eccentric, filled with hyaline periphyses. Peridium 15–37 μm (x ̅ = 25 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, some branched, filamentous, smooth-walled pseudoparaphyses. Asci 35–70 × 7–12 μm (x ̅ = 48 × 8.5 μm, n = 30), 8 - spored, bitunicate, fissitunicate, clavate to cylindric-clavate, short stalked, some with club-shape pedicel, apically rounded, with small ocular chamber. Ascospores 10–13 × 3–5 μm (x ̅ = 12 × 4 μm, n = 50), 1–2 - seriate, overlapping, fusoid to ellipsoid, tapering towards the blunt ends, or blunt at both ends, straight or slightly curved, guttulate, smooth-walled, subhyaline to slightly brown when young, 1 - septate; yellowish-brown to dark brown when mature, becoming 3 - septate, 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 35–38 mm in diameter after one month at 25 ° C in dark. Colonies from above, white in the whole colony and raised in the central point, circular, margin well-defined, aerial mycelia dense; in reverse, grayish green in the center, white ring at the margin, no pigmentation on PDA.

Material examined.

China • Guizhou Province, Guiyang City , Huaxi District, 26°30'40"N, 106°39'30"E, elevation 1,155 m, on dead branches of medicinal plant Camellia sinensis (Linnaeus) Kuntze ( Theaceae ), 2 February 2023, Y. X. Yu & Y. H. Lu, GY 15 ( HKAS 131992 , holotype; HUEST 23.0295 , isotype), ex-holotype living culture CGMCC 3.25689 ; ex-isotype living culture UESTCC 23.0295 .

Notes.

Nigrograna peruviensis was reported by Kolařík et al. (2017) as an endophytic fungus ( Biatriospora peruviensis ) and was synonymized under the genus Nigrograna by Kolařík (2018), but with a lack of detailed morphological structures. In this study, our isolates of N. guttulata ( CGMCC 3.25689 and UESTCC 23.0295 ) have a close phylogenetic relationship with N. peruviensis ( Kolařík et al. 2017; Kolařík 2018) based on ITS, LSU, rpb 2, SSU, and tef 1 - α sequence data, and formed a distinct lineage with absolute bootstrap support (100 % MLBS / 1.00 BIPP) (Fig. 1 ). Additionally, N. guttulata (ex-type strain, CGMCC 3.25689 ) can be distinguished from N. peruviensis (ex-type strain, CCF 4485) by 8 / 462 bp (1.7 %, 3 gaps) in ITS, 24 / 1020 bp (2.4 %, without gaps) in LSU and 10 / 618 bp (1.6 %, without gaps) in rpb 2 differences. Therefore, the establishment of the new species N. guttulata is justified by the phylogenetic evidence.

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 9. Nigrograna guttulata (HKAS 131992, holotype) a host Camellia sinensis b branch of Camellia sinensis c – e appearance of ascomata on host surface f vertical section through ascoma g peridium h hamathecium i germinated ascospore j, k colony on PDA, above (j) and below (k) l – n, t asci o – s ascospores. Scale bars: 50 µm (f); 40 µm (g); 10 µm (h, i, l – n, t); 5 µm (o – s).