Melomastia beihaiensis T.Y. Du, K.D. Hyde & Tibpromma, sp. nov.
Index Fungorum number: IF 558764; MycoBank number: MB 558764; Facesoffungi number: FoF 10262; Fig. 1
Etymology – based on “Beihai” where the fungus was collected.
Saprobic on dead stems of Chromolaena odorata (L.) R.M.King & H.Rob. Sexual morph: Ascomata (including neck) 250–360 µm high × 200–340 µm diam. (x=302×241 µm, n=10), clearly visible on the host surface as dark, raised spots, solitary or aggregated, semi-immersed to immersed, dark brown to black, uni-loculate, clypeate to wide subglobose, irregular bottom, long ostiolate, black, carbonaceous. Ostiolar canal 150–230 µm high×115–185 µm diam. (x=183×158 µm, n=10), surrounded by a layer of clypeus, thick, dense, black cells, filled with hyaline cells, periphyses absent. Peridium 5–25 µm wide (x =13 µm, n=20), comprising an outer layer of dense, dark brown cells of textura angularis to textura prismatica, becoming lighter inwardly, fused with host tissues. Hamathecium 1.5–2.5 µm wide, comprising numerous, hyaline, aseptate, unbranched pseudoparaphyses, longer than asci, attached at the base and between the asci, embedded in a gelatinous matrix. Asci (125–)135–190×5–7 µm (x=163×5.9 µm, n=20), 8-spored, bitunicate, cylindrical, extremely shortpedicellate, rounded at the apex. Ascospores 16–28×5–7 µm (x=22×5.8 µm, n=30), overlapping-uniseriate, hyaline, broadly fusiform, conical at upper part and the lower end is truncate, 3-septate, constricted at the septa, constricted at the central septum where the spore seem likely to separate into two parts, smooth-walled, with a large guttule in each cell when spores are mature, not surrounded by a mucilaginous sheath. Asexual morph: Undetermined.
Culture characteristics – Colonies on PDA reaching 5 cm diam., after 20 days at room temperature (20–25 ℃), white to pale orange, irregular in shape, margin filiform, with white aerial mycelia; reverse orange to brown, smooth, producing pigments in culture.
Material examined – China, Guangxi Province, Beihai, Yinhai District, Yintan Middle Road, 20° 54′ 34″ N 108° 50′ 46″ E, on dead stems of Chromolaena odorata (Asteraceae), 6 October 2020, Tianye Du, BHD23 (HKAS 121125, holotype), ex-type culture, KUMCC 21-0084.
GenBank numbers – ITS: MZ726997, LSU: MZ726990, SSU: MZ727002, tef1-α: OK043822
Notes – In the combined LSU, SSU and tef1-α gene analysis (Fig. 2), our collection forms a distinct clade which is basal to Melomastia distoseptata, M. fusispora, M. oleae, M. thamplaensis and M. winteri with ML=99% and BI=1.00 bootstrap support. Our collection differs with these genetically close Melomastia species viz. Melomastia distoseptata has septate pseudoparaphyses and 3-distoseptate ascospores, M. fusispora has ascospores with a gelatinous sheath, M. oleae has periphyses in the ostiolar canal, M. thamplaensis has immersed ascoma and peridium with cells of textura angularis and M. winteri has septate pseudoparaphyses (Zhang et al. 2017a; Hongsanan et al. 2020a, b; Li et al. 2022a, b). Melomastia chromolaenae has also been reported from Chromolaena odorata, however, our collection is morphologically different from M. chromolaenae having aseptate, unbranched pseudoparaphyses, broadly fusiform ascospores with 3-septa when mature, while M. chromolaenae has septate, branched pseudoparaphyses, fusiform ascospores with 9–11-septate when mature (Mapook et al. 2020). Therefore, we introduce our collection as a new species, Melomastia beihaiensis.
Figure 1 – Melomastia beihaiensis (HKAS 121125, holotype). a–c Appearance of ascomata on the substrate. d, e Vertical sections through the ascomata. f Ostiole. g Pseudoparaphyses. h Peridium. i, j Asci. k–m Ascospores. n Germinated ascospore. o Colonies on PDA surface and reverse view. Scale bars: e–g, i, j=100 µm, h, k–n=20 µm
Figure 2 – Phylogram generated from maximum likelihood analysis based on combined LSU, SSU and tef1-α sequence data which comprised 2857 base pairs of LSU=927, SSU=1009, tef1-α=921. The best scoring RAxML tree with a final likelihood value of − 13,807.470835 is presented. The matrix had 1012 distinct alignment patterns, with 25.91% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.241219, C=0.268619, G=0.288053, T=0.202109; substitution rates: AC=0.779939, AG=2.032527, AT=1.173704, CG=0.889636, CT=7.202155, GT=1.0; gamma distribution shape parameter α=0.220289. Bootstrap support for maximum likelihood (ML) equal to or greater than 50% and clade credibility values greater than 0.90 from Bayesian inference analysis are labelled at each node. Ex-type strains are in bold, while the new isolates are indicated in blue bold. The tree is rooted to Anisomeridium phaeospermum (MPN539) and Anisomeridium ubianum (MPN94)