Arthrinium guangdongense H.J. Zhao, Manawas., & K.D. Hyde,

MycoBank number: MB 559550; Index Fungorum number: IF 559550; Faces of fungi number: FoF14656;

Etymology – Epithet refers to the Guangdong province, China, from where the fungus was collected.

Holotype – ZHKU 22-0003

Saprobic on dead culms of bamboo. Sexual morph: Not observed. Asexual morph: Conidiomata 70 µm length × 65 µm diam, semi-immersed in the substrate, solitary, gregarious or confluent, globose to subglobose, dark brown to black. Conidiomatal wall 5–60 µm composed of dark brown, thick-walled cells, becoming thin-walled and hyaline toward the inner region. Conidiophores 10–90 × 1–5 μm (x̅ = 32 × 2 μm, n=40) basauxic, straight or flexuous, cylindrical, hyaline, smooth-walled, aseptate. Conidiophores reduced to conidogenous cells. Conidiogenous cells 1–10 × 1–5 μm (x̅ = 3 × 2 μm, n=20), monoblastic or polyblastic, terminal, determinate, cylindrical, hyaline to light brown, smooth, aggregated, ampulliform. Conidia 5–10 × 5–10 µm (x̅ = 10 × 10 μm, n = 50), dark brown walled, smooth, aseptate, ovoid or round.

Culture characteristics – Colonies on PDA reach 6–8 cm diam. after 15 days at 25°C. Colonies circular, medium dense, flattened, white radial, margin undulate, aerial hyphae. Reverse white with, producing a green pigment, becoming tawny from the center.

Material examined – Danxia Mountain, Renhua County, Shaoguan City, Guangdong Province, China, isolated from a dead twig of Bamboo plant, E 113°44′22″, N 25°2′39″ 17 November 2020, H.J. Zhao and YR Xiong. (ZHKU 22-0003, holotype); living cultures ZHKUCC 22-0003, ZHKUCCC 22-0002.

Notes – In the phylogenetic analysis, two isolates obtained in this study developed a sister clade to Arthrinium guizhouense (Wang & Cai 2018) with 100% ML, 100% MP and 1.00 BYPP. Arthrinium guizhouense was introduced from the air in a karst cave in Guizhou province, China, by Wang et al. (2018). The two strains (ZHKUCC 22-0002 and LC 5322) have 23 base pair differences in the ITS regions (631 bp), 53 base pair differences in the LSU regions (868 bp), 9 base pair differences in the tef1-α regions (478 bp) and 11 base pair differences in the β-tubulin regions (543 bp). Morphologically, Arthrinium guangdongensis differs from the type specimen (LC 5322) in the morphology of conidiomata, the size of conidia is also different. Based on this trivial difference in morphological and molecular data, we introduced the isolates obtained in this study as a new species.

FIGURE 3. Arthrinium guangdongense (ZHKUCC 22-0003 Holotype). (a-b) Conidiomata on host surface. (c-d) Section through conidiomata. (e-f) Conidia (g) Germinated conidium. (h-i) Culture on PDA from above and bleow. (j) Conidial mass on cultures. (k) Conidiophores. (l) Conidia with conidiogenous cells. (m) Conidia grown on PDA plate. Scale bars: b= 200 μm,c-f= 10 μm. g= 5 μm. k-m= 10 μm.