Melomastia aquilariae T.Y. Du & Karun. sp. nov.

Index Fungorum number: IF 902121; Mycobank number: MB 902121; Facesoffungi number: FoF 15849; Fig. 1

Etymology – named after the host genus, Aquilaria.

Holotypy – HKAS 126527

Saprobic on dead stems of Aquilaria sinensis. Sexual morph: Ascomata (excluding neck) 350–700 µm high×300–450 µm diam. (x̄=524×377 µm, n=10), solitary, semi-immersed to immersed, visible on the host surface as dark, raised spots, dark brown to black, uniloculate,
globose to subglobose (wide at the base), carbonaceous. Ostiolar canal 100–150 µm high, black, conical, carbonaceous, papillate, with periphyses. Peridium 35–150 µm wide (x̄=85 µm, n=10), comprising dense, brown to darkbrown cells of textura angularis to textura prismatica, fusion with host tissue. Hamathecium 1–3 µm wide, comprising numerous, hyaline, branched, septate pseudoparaphyses, longer than asci, attached at the base and between the asci. Asci 145–220×7.5–9 µm (x̄=186×8.5 µm, n=30), bitunicate, 8-spored, cylindrical, cylindrical pedicellate 7–14 µm long, rounded in apex, J- apical ring. Ascospores
21.5–28 × 7–8 µm (x̄= 25 × 7.5 µm, n = 30), 3-septate, overlapping-uniseriate, hyaline, fusiform with acute ends, slightly constricted at the septum, smooth-walled, with a large guttule in each cell when mature, not surrounded by a mucilaginous sheath. Asexual morph: Not observed.

Culture characteristics – Colonies on PDA reaching 6 cm diam., after one month at 28℃; grey, soft, irregular shape, middle protrusion, filiform margin; pale yellow to dark grey, smooth in reverse (Fig. 1). Specimen examined: China, Yunnan Province, Xishuangbanna, Jinghong City, Naban River Nature Reserve, 22° 7′ 50″ N, 100° 40′ 29″ E, on dead stems of Aquilaria sinensis (Thymelaeaceae), 14 September 2021, T.Y, YNA52, (HKAS 126527, holotype), ex-type ZHKUCC:23-0073, ex-isotype ZHKUCC:23-0088.

GenBank numbers – ZHKUCC:23-0073: LSU=OR807856; SSU=OR807854; tef1-α=OR832867; ZHKUCC:23-0088: LSU=OR807857; SSU=OR807855; tef1-α=OR832868.

Notes – Based on the results of BLAST analysis in NCBI GenBank, in LSU, Melomastia aquilariae gave 99.65% closest match to M. oleae (CGMCC 3.20619), 99.90% for SSU with the closest match M. fusispora (CGMCC 3.20618) and 98.86% for tef1-α with the closest matches M. winteri (CGMCC 3.20621). In the phylogenetic analyses of this study, M. aquilariae formed a sister branch with M. winteri (CGMCC 3.20621) with 97% ML bootstrap support (Fig. 2). However, M. aquilariae is different from M. winteri in having solitary, globose to subglobose ascomata, branched pseudoparaphyses, and colonies grey, soft, irregular shape in PDA; while M. winteri has solitary, gregarious, globose ascomata, unbranched pseudoparaphyses, and colonies white, dense, circular in PDA (Li et al. 2022). In addition, M. aquilariae can be distinguished from M. winteri by its wider ascomata (524 × 377 µm vs. 352 × 387 µm), wider range of peridium (35–150 µm vs. 55–62.5 µm), larger asci (186×8.5 µm vs. 177×7.5 µm) and longer cylindrical pedicellate (7–14 µm vs. 4.8–6.5 µm) (Li et al. 2022). Furthermore, a comparison of tef1-α nucleotides between M. aquilariae and M. winteri (CGMCC 3.20621) resulted in 1.18% differences (10/845 bp, without gaps). In this study, M. aquilariae was collected from Aquilaria sinensis in China, while M. winteri was introduced from Olea europaea in China. Therefore, we introduce our collection as a new species based on both morphological study and phylogenetic analyses.

Figure 1 – Melomastia aquilariae (HKAS 126527 holotype). a, b Appearance of ascoma on the host. c Vertical sections through the ascoma. d Ostiole with periphyses. e–h Asci (h ascus stained with Melzer’s reagent). i Pseudoparaphyses. j Peridium. k–n Ascospores. o Germinated ascospore. p, q Colony on PDA surface and reverse view. Scale bars: c=300 µm, d=50 µm, e–h=50 µm, i=2 µm, j–o=20 µm

Figure 2 – Phylogram generated from maximum likelihood analysis based on combined LSU, SSU and tef1-α sequence data of 42 taxa, which comprised 2606 base pairs of LSU=764, SSU=968, tef1-α=874. The best scoring RAxML tree with a final likelihood value of − 10,654.707840 is presented. The matrix had 720 distinct alignment patterns, with 25.58% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.235408, C=0.264506, G=0.293087, T=0.206999; substitution rates: AC=0.801663, AG=1.998748, AT=1.048958, CG=0.946613, CT=8.369181, GT=1.000000; gamma distribution shape parameter α=0.590876. Bootstrap support values for maximum likelihood (ML) equal to or greater than 50% and clade credibility values equal to or greater than 0.90 from Bayesian inference analysis are labelled at each node. The new isolates are indicated in blue bold. The tree is rooted to Anisomeridium phaeospermum (MPN539) and A. ubianum (MPN94)