Melomastia diqingensis
Melomastia diqingensis G.C. Ren & K.D. Hyde (2024)
Index Fungorum number: IF901346; Facesoffungi Number: FoF13890
Holotype: HKAS 122718
Etymology: The species epithet “diqing” refers to the location where the species was collected.
Saprobic on dead woody twigs of Rhododendron rubiginosum. Sexual morph: Ascomata 320–600 μm high × 240–400 μm diam., (x̅ = 440 × 300 μm, n = 5), semi-immersed to immersed in host tissue, solitary or scattered, subglobose to obpyriform, coriaceous, black, with an ostiolar neck. Ostioles 195–210 × 130–180 μm (x̅ = 200 × 150 μm, n = 5), carbonaceous, black, papillate. Peridium 15–30 μm wide, 3–4 layered, composed of hyaline to brown cells of textura angularis and textura prismatica. Asci 100–127 × 5.5–6.7 μm (x̅ = 116 × 6 μm, n = 20), 8-spored, bitunicate, long cylindrical, straight or curved, apically rounded, short pedicellate, with a small ocular chamber. Ascospores 12.8–15 × 4–5 μm (x̅ = 14 × 4.5 μm, n = 30), uniseriate, oval to oblong, hyaline, 2-septate, slightly constricted at the septum, with guttules in each cell, with gelatinous sheath, thick and smooth-walled. Asexual morph: Undetermined.
Culture characteristics: Ascospores germinating on PDA within 24 h at room temperature (25 °C). Germ tubes produced from the apical cell of ascospore. Colonies on PDA, reaching 30 mm diameter after two weeks at 20–25 ℃, mycelia superficial, circular, undulate, umbonate, surface rough, yellowish at edge and white at center; reverse, yellowish.
Material examined: China, Yunnan Province, Diqing, on dead woody twigs of Rhododendron rubiginosum (Ericaceae), 20 August 2020, G.C. Ren, DQ19 (HKAS 122718, holotype), ex-type living culture KUMCC 21-0536.
GenBank numbers SSU: OQ168224, LSU: OQ170873, ITS: OQ158951, tef1-α: OR613413.
Notes: Melomastia diqingensis is introduced as a new species based on its distinct morphology and the phylogeny of the combined SSU, LSU, ITS, and tef1-α dataset. In our phylogenetic study, the new strain (KUMCC 21-0536) formed a sister clade to Melomastia italica (MFLUCC 15-0160) with 100% ML bootstrap support and 1.00 BYPP value (Fig. 7). Our species (KUMCC 21-0536) is similar to Melomastia italica in having subglobose to obpyriform, black ascomata, 8-spored, bitunicate, cylindrical asci and hyaline, 2-septate ascospores with a gelatinous sheath (Norphanphoun et al. 2017). However, Melomastia diqingensis differs from M. italica in having oval to oblong ascospores (12.8–15 × 4–5 μm), while M. italica has ellipsoid ascospores (8.8–10.5 × 2.8–4.1 μm) and asci with prominent apical ring (Norphanphoun et al. 2017). A pairwise nucleotide comparison showed that Melomastia diqingensis differs from M. italica in 5/860 bp of LSU (0.58%, without gaps) and 3/990 bp of SSU (0.3% without gaps) because Melomastia italica only has the sequence of LSU and SSU, therefore, we did not comparison base pair for tef1-α and ITS. Naziazeno & Aptroot (2023) described Melomastia septemseptata as a new species, based only on morphology, which was found on the living bark of a Cerrado tree in a dry, terrestrial environment from Brazil. However, M. septemseptata differs from M. diqingensis in having 7–9- septate ascospores.
Figure 1. Phylogram generated from ML analysis based on SSU, LSU, ITS, tef1-α, and rpb2 sequence data representing Pleurotremataceae. Related sequences are obtained following Li et al. (2022). Forty-six strains are included in the combined analyses, which comprise 3948 characters for SSU, LSU, ITS, tef1-α, and rpb2 alignment. Anisomeridium phaeospermum (MPN539) and A. ubianum (MPN94) were used as the outgroup taxa. The best-scoring RAxML tree with a final likelihood value of -28755.342067 is presented. The matrix had 2026 distinct alignment patterns, with 32.59% of undetermined characters or gaps. Estimated base frequencies were as follows; A = 0.238390, C = 0.263023, G = 0.288210, T = 0.210377; substitution rates AC = 1.022596, AG = 2.177198, AT = 1.179336, CG = 1.031321, CT = 5.495584, GT = 1.0000. The tree topology of the ML analysis is similar to the Bayesian analysis. Bootstrap values for ML equal to or greater than 70% and BYPP values greater than 0.95 (the rounding of values to 2 decimal proportions) are labelled on the nodes. Strains of the newly described species are in blue, while type strains are in bold.
Figure 2. Melomastia diqingensis (HKAS 122718, holotype). a Material examined. b Appearance of ascomata on the host substrate. c Section of an ascoma. d Vertical section through the ostiole. e Peridium. f Pseudoparaphyses. g–k Asci. l–n Ascospores. o Ascospore in Indian ink showing sheath. p Germinated ascospore. q, r Culture characters on PDA (q = from above, r = from below). Scale bars: c, d = 100 μm, e = 30 μm, f = 10 μm, g–k = 50 μm, l–p = 10 μm, q, r = 10 mm.
References
- Ren GC, Jayasiri SC, Tibpromma S, De Farias ARG, et al. (2024) Saprobic ascomycetes associated with woody litter from the Greater Mekong Subregion (Southwestern China and Northern Thailand). Mycosphere 15(1), 954–1082, Doi 10.5943/mycosphere/15/1/8
Recent Genus
EpicoccumAmphisphaeria
Paraeutypella
Recent Species
Epicoccum diplopterygiiTorula chromolaenae
Periconia delonicis