Nigrograna longiorostiolata 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 longiorostiolata H. Z. Du & Jian K. Liu sp. nov.

Fig. 3

Etymology.

The epithet ‘ longiorostiolata ’ refers to the longer-ostiolate of ascomata.

Holotype.

HKAS 131311

Description.

Saprobic on dead branches of Citrus medica ( Rutaceae ). Sexual morph: Ascomata 222–293 μm wide, 144–486 μm high (x ̅ = 264 × 303 μm, n = 20), solitary, scattered, immersed, visible as black dots on the host surface, uniloculate, globose to subglobose, sometimes obpyriform with a long ostiole. Ostioles 175–302 μm long, 83–128 μm wide (x ̅ = 263 × 102 μm, n = 20) central or eccentric, longer, with a crest-like apex, filled with hyaline or slightly brown periphyses. Peridium 17–32 μm (x ̅ = 23.5 μm, n = 20) composed of textura prismatica cells, consisting 3–4 layers, brown to dark brown of outer layer, hyaline to subhyaline of inner layer. Hamathecium 1–2 μm (x ̅ = 1.5 μm, n = 20) wide, composed of numerous, filiform, hyaline, aseptate or separate, rarely branched, guttulate, smooth-walled pseudoparaphyses. Asci 40–70 × 6–9 μm (x ̅ = 53 × 8 μm, n = 30), 5–8 - spored, bitunicate, fissitunicate, clavate, short cylindrical pedicellate with a swollen base, apically rounded, with a minute ocular chamber. Ascospores 10–13 × 4–6 μm (x ̅ = 12 × 5 μm, n = 50), 1–2 - seriate, partially overlapping, fusoid to ellipsoid, tapering towards the blunt ends, or blunt at both ends, guttulate, olivaceous to yellowish-brown when young, aseptate or 1 - septate; deeply constricted at septa, becoming 3 - septate, brown to dark brown when mature, 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 17–18 mm in diameter after three weeks at 25 ° C in dark, white in the whole colony from above, circular, edge entire, margin well-defined; in reverse, off-white to grayish brown, no pigmentation on PDA.

Material examined.

China • Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Mengla County, Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences . 21°56'1′′N, 101°25'33′′E, elevation 505 m, on dead branches of medicinal plant Citrus medica L. ( Rutaceae ), 10 November 2022, H. Z. Du, S 655 ( HKAS 131311 , holotype; HUEST 23.0200 , isotype); ex-holotype living culture CGMCC 3.25626 ; ex-isotype living culture UESTCC 23.0200 .

Notes.

Nigrograna longiorostiolata shares similar morphology with N. magnoliae (holotype, MFLU 20–0092) and N. kunmingensis (holotype, ZHKU 22-0141) in having immersed, globose to subglobose ascomata, bitunicate and clavate asci, fusoid to ellipsoid, 3 - septate mature ascospores. However, the ascomata size of N. longiorostiolata (222–293 × 144–486 μm) is larger than N. magnoliae (200–300 × 100–150 μm) ( Wanasinghe et al. 2020) and smaller than N. kunmingensis (300–500 × 390–450 µm) ( Liu et al. 2024). The phylogenetic result (Fig. 1 ) showed that N. longiorostiolata ( CGMCC 3.25626 and UESTCC 23.0200 ) can be recognized as a distinct phylogenetic species with high bootstrap support (100 % MLBS / 1.00 BIPP). Additionally, N. longiorostiolata (ex-type strain, CGMCC 3.25626 ) can be distinguished from N. magnoliae (ex-type strain, MFLUCC 20-0020) by 26 / 471 bp (5.5 %, 2 gaps) in ITS, 14 / 831 bp (1.7 %, without gaps) in LSU, 30 / 855 bp (3.5 %, 3 gaps) in tef 1 - α and 96 / 1042 bp (9.2 %, without gaps) in rpb 2 differences, and differs from N. kunmingensis (ex-type strain, ZHKUCC 22-0242) with 70 / 823 bp (8.5 %, 21 gaps) of ITS, 14 / 844 bp (1.7 %, without gaps) of LSU and 30 / 855 bp (3.5 %, 3 gaps) of tef 1 - α differences. Therefore, N. longiorostiolata associated with Citrus medica is a phylogenetically distinct specie and introduced as a new species.

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 3. Nigrograna longiorostiolata (HKAS 131311, holotype) a host Citrus medica b branch of Citrus medica c – f appearance of ascomata on host surface g, h vertical section through ascoma i peridium j germinated ascospore k, l colony on PDA, above (k) and below (l) m hamathecium n – p, w – z asci q – v ascospores. Scale bars: 100 µm (g, h); 10 µm (i, j, m – p, w – z); 5 µm (q – v).