Melomastia sinensis (Samarak., Tennakoon & K. D. Hyde) W. L. Li, Maharachch. & Jian K. Liu (2022)

Du, Tian-Ye, Karunarathna, Samantha C., Tibpromma, Saowaluck, Hyde, Kevin D., Nilthong, Somrudee, Mapook, Ausana, Liu, Xiang-Fu, Dai, Dong-Qin, Niu, Chen, Elgorban, Abdallah M., Chukeatirote, Ekachai & Wang, Hao-Han, 2024, Melomastia (Dothideomycetes, Ascomycota) species associated with Chinese Aquilaria spp., MycoKeys 111, pp. 65-86 : 65-86

Melomastia sinensis (Samarak., Tennakoon & K. D. Hyde) W. L. Li, Maharachch. & Jian K. Liu (2022)

Fig. 3

Description.

Saprobic on a dead branch of Aquilaria sp. Sexual morph: Ascomata (excluding neck) 400–600 µm high × 430–580 µm diam. (x – = 515 × 520 µm, n = 10), solitary, scattered to gregarious, semi-immersed to immersed, erumpent through host tissue, globose to subglobose, black, coriaceous to carbonaceous, ostiolate. Ostiolar canal 230–365 µm high × 200–260 µm wide (x – = 303 × 230 µm, n = 10), central, black, conical, coriaceous to carbonaceous, filled with hyaline sparse periphyses. Peridium 30–120 µm wide (x – = 75 µm, n = 20), comprising dense, several layers of thick-walled cells of textura angularis to textura prismatica, outer layers brown to dark brown, becoming lighter inwardly. Hamathecium comprising 2.5–6.5 µm wide, numerous filamentous, filiform, septate, unbranched, hyaline pseudoparaphyses, attached to the base and between the asci, embedded in a gelatinous matrix. Asci 175–220 × 8.5–11.5 µm (x – = 195 × 10.5 µm, n = 30), bitunicate, 8 - spored, cylindrical, long pedicel, thickened and rounded apex, with an obvious ocular chamber. Ascospores (17.5 –) 20–26.5 × 7–9 µm (x – = 24 × 8 µm, n = 30), overlapping-uniseriate, hyaline, when ascospores gather together, they appear light yellow, mostly 6–7 - septate at maturity, 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 most cells, germinated ascospores appear light yellow. Colonies on PDA reaching 3 cm diam., after two weeks at 23–28 ° C. Colonies obverse: dense, circular or irregular, umbonate, cream, light yellow at the center, entire or undulate edge. Colonies reverse: dark gray, yellow at the margin.

Material examined.

China • Yunnan Province, Xishuangbanna, Jinghong City, Naban River Nature Reserve , 22°7'48"N, 100°40'24"E, on a dead branch of Aquilaria sp. ( Thymelaeaceae ), 14 September 2021, Tianye Du, YNA 41 ( GMB-W 1006 , new host and geographical record), living culture, GMBCC 1008 .

Host and distribution.

Aquilaria sp. ( China; this study), Camellia sinensis ( Thailand; Hyde et al. 2018), and Hevea brasiliensis ( Thailand; Senwanna et al. 2021).

Notes.

In the phylogenetic analyses, our new collection ( GMBCC 1008) isolated from a dead branch of Aquilaria sp. grouped with Melomastia sinensis strains ( MFLUCC 17-1344, MFLUCC 17-2606 and MFLU 17-0777) in Melomastia sensu lato, with a 99 % ML / 0.93 PP bootstrap support (Fig. 1 ). NCBI BLASTn searches of our collection showed 99.78 % similarity to M. sinensis ( MFLUCC 17-2606) in the LSU sequence, 99.21 % similarity to M. oleae ( UESTCC 21.0006) in the SSU sequence, and 99.67 % similarity to M. sinensis ( MFLUCC 17-2606) in the TEF sequence.

Melomastia sinensis (= Dyfrolomyces sinensis Samarak., Tennakoon & K. D. Hyde ) was introduced by Hyde et al. (2018) as a saprobic on Camellia sinensis ( L.) Kuntze stems. Our new collection shares a similar morphology with M. sinensis ( MFLU 17-0777, holotype) in cylindrical ascospores with 6–7 - septate ascospores. Our new collection has semi-immersed to immersed ascomata, differs from M. sinensis ( MFLU 17-0777, holotype) in having superficial ascomata ( Hyde et al. 2018) and differs from immersed ascomata in M. sinensis ( MFLU 19-0232) ( Senwanna et al. 2021). However, the nucleotide base pair differences between our new collection ( GMBCC 1008) and M. sinensis ( MFLUCC 17-1344, ex-type) showed that the LSU and SSU gene has no nucleotide differences, while the TEF gene of M. sinensis ( MFLUCC 17-1344, ex-type) is unavailable in NCBI ( Hyde et al. 2018). The comparison of the TEF nucleotides between the new collection and another strain of M. sinensis ( MFLUCC 17-2606) resulted in 0.3 % differences (3 / 873 bp, without gaps) ( Senwanna et al. 2021). This study first discovered M. sinensis on Aquilaria sp. in China. Therefore, we introduce our new collection as a new host and geographical record of M. sinensis based on both morphological study and phylogenetic analyses.

Figures

Figure 1. Phylogram generated from maximum likelihood analysis based on combined LSU, SSU, and TEF sequence data of 50 taxa. Bootstrap support values for maximum likelihood (ML) equal to or greater than 60 % and clade credibility values greater than 0.90 from Bayesian inference analysis are labelled at each node. The tree is rooted with Anisomeridium phaeospermum (MPN 539) and A. ubianum (MPN 94). The new isolates are indicated in red, and the ex-type strains are in bold.

Figure 3. Melomastia sinensis (GMB-W 1006, new host and geographical record) A – C appearance of ascomata on the host (A the arrows indicate ascomata) D vertical sections through the ascoma E ostiole F peridium G pseudoparaphyses H asci I ascus with an ocular chamber J, K ascospores L germinated ascospore M, N colony on PDA obverse and reverse view. Scale bars: 200 µm (D, E); 100 µm (H); 50 µm (F); 20 µm (I – L); 10 µm (G).