Melomastia yunnanensis T. Y. Du, K. D. Hyde, Tibpromma & Karun. 2024, sp. nov.

Melomastia yunnanensis T. Y. Du, K. D. Hyde, Tibpromma & Karun. sp. nov. Fig. 4 Etymology. Named after the type location “ Yunnan, China ”. Holotype. GMB-W 1007 Description. Saprobic on a dead branch of Aquilaria sp. Sexual morph: Ascomata (excluding neck) 400–500 µm high × 300–480 µm diam. (x – = 458 × 395 µm, n = 10), solitary, scattered to gregarious, immersed to erumpent through host tissue, globose, black, carbonaceous, ostiolate. Ostiolar canal 100–160 µm high × 120–230 µm wide (x – = 130 × 184 µm, n = 10), central, black, conical, carbonaceous, filled with hyaline sparse periphyses. Peridium 25–75 µm wide (x – = 55 µm, n = 10), comprising of dense, several layers of brown to dark brown, thick-walled cells of textura angularis to textura prismatica. Hamathecium comprising 2.5–7.5 µm wide, numerous filamentous, filiform, septate, sometimes branched, hyaline pseudoparaphyses, attached to the base and between the asci, embedded in a gelatinous matrix. Asci 180–220 × 7.5–10.5 µm (x – = 195.5 × 9 µm, n = 30), bitunicate, 8 - spored, cylindrical, short pedicel, thickened and rounded apex, with an obvious ocular chamber. Ascospores 20–24.5 × 6–8 µm (x – = 22.5 × 7 µm, n = 30), overlapping-uniseriate, hyaline, when ascospores gather together, they appear light yellow, mostly 6–8 - septate at maturity, mostly 7 - septate, cylindrical, with rounded ends, slightly constricted at the septum, often similar width of cells with several small guttules, not surrounded by a mucilaginous sheath. Asexual morph: Undetermined. Culture characteristics. Ascospores germinated on PDA after 24 hours, germ tubes were produced from both ends, germinated ascospores appear light brown. Colonies on PDA reaching 2 cm diam., after two weeks at 23–28 ° C. Colonies obverse: dense, circular, umbonate, gray at the center, cream, and entire edge. Colonies reverse: gray brown, light brown at the margin. Material examined. China • Yunnan Province, Xishuangbanna, Jinghong City, Naban River Nature Reserve, 22°7'51"N, 100°40'21"E, on a dead branch of Aquilaria sp. (Thymelaeaceae), 14 September 2021, Tianye Du, YNA 51 (GMB-W 1007, holotype), ex-type, GMBCC 1009, other living culture, GZCC 23-0621. Notes. In the phylogenetic analyses, our new collection, M. yunnanensis formed a sister branch with M. sinensis (MFLUCC 17-1344, MFLUCC 17-2606, MFLU 17-0777, and GMBCC 1008) in Melomastia sensu lato with a 100 % ML / 1.00 PP bootstrap support (Fig. 1). NCBI BLASTn searches of our collection M. yunnanensis showed 99.23 % similarity to M. sinensis (MFLUCC 17-2606) in the LSU sequence, 98.92 % similarity to M. thamplaensis (AND 9) in the SSU sequence, and 96.34 % similarity to M. sinensis (MFLUCC 17-2606) in the TEF sequence. Our new collection, M. yunnanensis shares similar morphology with M. sinensis in cylindrical and septate ascospores. However, M. sinensis differs from M. yunnanensis in having superficial, semi-immersed to immersed ascomata, cylindrical or conical ostiolar canal, and unbranched pseudoparaphyses (Hyde et al. 2018), while our M. yunnanensis has immersed ascomata, conical ostiolar canal, and pseudoparaphyses sometimes branched. In addition, the nucleotide base pair differences between our new collection M. yunnanensis (GMBCC 1009, ex-type) and M. sinensis (MFLUCC 17-1344, ex-type) showed the LSU gene has 0.5 % nucleotide differences (4 / 760 bp, without gaps), the SSU gene has 0.5 % nucleotide differences (4 / 813 bp, without gaps), while the TEF gene of M. sinensis (MFLUCC 17-1344, ex-type) is unavailable (Hyde et al. 2018). We compared the TEF nucleotides between the new collection and another collection of M. sinensis (MFLUCC 17-2606), which resulted in 3.8 % differences (33 / 873 bp, without gaps) (Senwanna et al. 2021). Therefore, we introduce our new collection, M. yunnanensis, as a new species on a dead branch of Aquilaria sp. from terrestrial habitats in China, based on both morphological study and phylogenetic analyses following the guidelines of Maharachchikumbura et al. (2021).