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

Xiong, Yinru, Hyde, Kevin D., Lu, Li, Harishchandra, Dulanjalee L., Mapook, Ausana, Xu, Biao, Alotibi, Fatimah & Manawasinghe, Ishara S., 2024, Novel Helicoma and Neohelicosporium (Tubeufiaceae, Tubeufiales) species and two new host records of Helicoma on tropical palms (Arecaceae) from China, MycoKeys 108, pp. 287-315 : 287-315

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.

Figures

Figure 4. Helicoma rufum (MHZU 23-0168, new host record) a specimen observed b, c colony on decaying Caryota mitis d, e conidiophores f – i conidiogenous cells j – l conidia m germinated conidium. Scale bars: 50 μm (d, e, m); 10 μm (f – i); 20 μm (j – l).