Melomastia guangdongensis T. Y. Du, K. D. Hyde, Tibpromma & Karun., 2024

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 guangdongensis T. Y. Du, K. D. Hyde, Tibpromma & Karun. sp. nov.

Fig. 2

Etymology.

Named after the type locality “ Guangdong, China ”.

Holotype.

MHZU 23-0021

Description.

Saprobic on a dead branch of Aquilaria sinensis . Sexual morph: Ascomata (excluding neck) 180–360 µm high × 200–300 µm diam. (x – = 267 × 245 µm, n = 10), visible as black dots on the host surface, black, solitary, scattered to gregarious, semi-immersed to immersed, uniloculate, globose to subglobose, coriaceous to carbonaceous, ostiolate. Ostiolar canal 190–240 µm high × 120–160 µm wide (x – = 214 × 140 µm, n = 10), central, black, cylindrical, coriaceous to carbonaceous, filled with hyaline cells. Peridium 30–60 µm wide (x – = 40 µm, n = 20), comprising dense, several layers, outer layers brown to dark brown, thick-walled cells of textura angularis to textura globulosa, inner layers hyaline, thin-walled cells of textura angularis to textura prismatica, not fusion well with host tissue. Hamathecium comprising 1.5–3 µm wide, numerous filamentous, filiform, septate, sometimes branched, hyaline, pseudoparaphyses, attached to the base and between the asci, embedded in a gelatinous matrix. Asci 120–168 × 5.5–7.5 µm (x – = 144 × 6.5 µm, n = 30), bitunicate, 8 - spored, cylindrical, short pedicel, rounded in apex, with an obvious ocular chamber. Ascospores (18.7 –) 20–26 × 5–7 µm (x – = 23 × 6 µm, n = 30), overlapping-uniseriate, hyaline, 3 - septate at maturity, fusiform with acute ends, slightly constricted at the middle septum, smooth-walled, 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. Colonies on PDA reaching 3 cm diam., after two weeks at 23–28 ° C. Colonies obverse: dense, circular, white, velvety, slightly raised at the center, entire edge. Colonies reverse: yellow, cream at the margin.

Material examined.

China • Guangdong Province, Maoming City, Dianbai District, Poxin , 21°34'28"N, 111°7'39"E, on a dead branch of Aquilaria sinensis ( Thymelaeaceae ), 3 June 2022, T. Y. Du, MMA 14 , ( MHZU 23-0021 , holotype), ex-type, GMBCC 1046 , other living culture, ZHKUCC 23-0040 .

Notes.

In the phylogenetic analyses, our new collection, M. guangdongensis formed a sister branch with M. thamplaensis strains ( HKAS 122773, KUMCC 21-0671, and MFLUCC 15-0635) in Melomastia sensu lato clade (Fig. 1 ) with a 75 % ML / 0.91 PP bootstrap support. NCBI BLASTn searches of our collection, M. guangdongensis showed 99.88 % similarity to M. thamplaensis ( HKAS 122773) in the LSU sequence, 100 % similarity to M. thamplaensis ( AND 9) in the SSU sequence, and 98.17 % similarity to M. thamplaensis ( KUMCC 21-0671) in the TEF sequence. Our new collection, M. guangdongensis shares similar morphology with M. thamplaensis in the shape of asci and ascospores. However, M. thamplaensis differs from M. guangdongensis in having clypeate, raised spots, immersed, subglobose to obpyriform, some with broad, flattened base ascomata, and three strata of peridium ( Zhang et al. 2017), while M. guangdongensis has semi-immersed to immersed, globose to subglobose ascomata, and two strata of peridium. Base pair differences of the LSU and SSU genes between our new collection M. guangdongensis ( GMBCC 1046, ex-type) and M. thamplaensis ( MFLUCC 15-0635, ex-type) showed that there are no nucleotide differences, while the TEF has 1.6 % nucleotide differences (14 / 865 bp, without gaps), and a comparison of the TEF nucleotides between new collections and another strain of M. thamplaensis ( KUMCC 21-0671) resulted in 1.7 % differences (15 / 865 bp, without gaps) ( Zhang et al. 2017; Ren et al. 2024). Therefore, we introduce our collection, M. guangdongensis , as a new species on a dead branch of Aquilaria sinensis from terrestrial habitats in China, based on both morphology and phylogenetic analyses following the guidelines of Maharachchikumbura et al. (2021).

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 2. Melomastia guangdongensis (MHZU 23-0021, holotype) A – C appearance of ascomata on the host (the arrows indicate ascomata) D, E vertical sections through the ascomata F ostiole G – J asci (I, J asci stained with cotton blue, and arrows indicate ocular chambers) K pseudoparaphyses stained with cotton blue L – O ascospores (O ascospore stained with cotton blue) P germinated ascospore Q colony on PDA obverse and reverse view. Scale bars: 200 µm (D – F); 50 µm (G – J); 10 µm (K – P).