Helicoma rufum Y. Z. Lu, J. C. Kang & K. D. Hyde

Helicoma rufum Y. Z. Lu, J. C. Kang & K. D. Hyde, Fungal Diversity 92: 131–344 (2018) Fig. 4 Description. Saprobic on the rotting inflorescence of Caryota mitis. Sexual morph: Not observed. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, effuse, gregarious, pale brown. Mycelium composed of partly immersed, partly superficial, hyaline to brown, septate, branched hyphae. Conidiophores 150–270 µm long, 4–7.5 µm wide (x ̄ = 225 × 5.9 μm, n = 20), macronematous, mononematous, cylindrical, erect, straight to slightly bent, pale brown to deep brown from top towards the base, apex hyaline, septate, mostly unbranched, smooth-walled. Conidiogenous cells 7–15 μm long, 4–7 μm wide (x ̄ = 12 × 5.9 μm, n = 20), mono- to polyblastic, cylindrical, integrated, intercalary, brown, smooth-walled; with denticles, 3–6 μm long, 1.5–3 μm wide (x ̄ = 4.6 × 2.5 μm, n = 20), arising from the lower portion of conidiophores as tooth-like protrusions, mono- to polyblastic, pale brown to brown, smooth-walled. Conidia 21–47 μm diam. (x ̄ = 36.2 μm, n = 40) and conidial filament 2–5 μm wide (x ̄ = 3.8 μm, n = 40), 145–345 μm long (x ̄ = 257.7 μm, n = 40), solitary, pleurogenous, tightly coiled 3–4 ½ times, guttulate, become loose in water, hyaline to pale brown, 25–35 - septate, smooth-walled. Culture characteristics. Conidia germinating on water agar and germ tubes produced from conidia within 12 h. Colonies growing on PDA attaining 3 cm diam. after six weeks at 25 ° C, irregular, undulate, rough, superficial and partially immersed, brown aerial mycelium mixed with pale brown; reverse brown with pale brown. Material examined. China, Yunnan Province, Xishuangbanna City, an unidentified forest beside National Highway 219 (21 ° 93 ' N, 101 ° 24 ' E, 549.6 m), rotting inflorescence of the Caryota mitis, 5 February 2023, Y. R. Xiong and Li Lu, XG 217 (MHZU 23-0168, new host record; living culture, ZHKUCC 24-0143, ZHKUCC 24-0144). Notes. Two isolates on rotting inflorescence of Caryota mitis obtained in this study clustered with the H. rufum clade in the phylogenetic tree with 96 % ML, 95 % MP bootstrap values and 0.99 BIPP bootstrap support. The nucleotide differences between H. rufum (ZHKUCC 24-0143) and H. rufum (MFLUCC 17-1806) are LSU: 0.09 % (1 / 1171 base pairs), tef 1 - α: 0.22 % (2 / 912 base pairs), rpb 2 sequence unavailable and no difference in ITS, excluding gaps. Our collection is similar to H. rufum (Lu et al. 2018 b) in the shape, colour and size of conidia (Table 3). Although the conidiophores and conidia are longer than in previous collections, this might be because the collections came from a different area, resulting in branching at the top of the conidiophores. Therefore, based on phylogenetic and morphological analysis, we identified our isolates as a new host record of H. rufum on Caryota mitis. Helicoma rufum was introduced from decaying wood in Thailand by Lu et al. (2018 b), based on the distinguished phylogenetic clade, wider conidiophores and larger tooth-like conidiogenous protrusions and larger conidia.