Helicoma guttulatum Y. Z. Lu, Boonmee & 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 guttulatum Y. Z. Lu, Boonmee & K. D. Hyde , Fungal Diversity 80: 1–270 (2016)

Fig. 3

Description.

Saprobic on the rotting petiole of Caryota mitis . Sexual morph: Not observed. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, effuse, gregarious, brown. Mycelium composed of partly immersed, partly superficial, brown, septate hyphae. Conidiophores 75–225 μm long, 5.5–6 μm wide (x ̄ = 152 × 5.7 μm, n = 20), macronematous, crowded, erect, straight to slightly bent, brown, deep brown towards the base, septate, branched, smooth-walled with irregular inclusion. Conidiogenous cells 10–29 μm long, 5–8.8 μm wide (x ̄ = 18 × 6.3 μm, n = 20), mono- to polyblastic, integrated, cylindrical, terminal, pale brown to brown, smooth-walled with irregular inclusion; with denticles, 1.6–3.5 μm long, 1.6–2.5 μm wide (x ̄ = 2.4 × 2.1 μm, n = 20), arising from the apex portion of conidiophores as tooth-like protrusions, mono- to polyblastic, brown, smooth-wall. Conidia 21–30 μm diam. (x ̄ = 25.1 μm, n = 40) and conidial filament 7.2–10 μm wide (x ̄ = 8.4 μm, n = 40), 48–69 μm long (x ̄ = 57.4 μm, n = 40), solitary, acropleurogenous, tightly coiled 1 ½ times, guttulate, not becoming loose in water, hyaline to pale brown, tapering towards flat end, 8–9 - septate, rounded at the apex, conic truncate at the base, 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 unknown forest beside National Highway 219 (21 ° 93 ' N, 101 ° 24 ' E, 549.6 m elev.), rotting petiole of the Caryota mitis , 5 February 2023, Y. R. Xiong and Li Lu, XG 215 ( MHZU 23-0166 , new host record; living culture, ZHKUCC 24-0139 , ZHKUCC 24-0140 ).

Notes.

Two isolates on rotting petiole of the Caryota mitis obtained in this study clustered with the H. guttulatum clade, based on the phylogenetic tree with 100 % ML, 100 % MP bootstrap support and 0.91 BIPP bootstrap support. The nucleotide differences excluding gaps between H. guttulatum ( ZHKUCC 24-0139 ) and H. guttulatum ( MFLUCC 16-0022 ) in ITS is 3.60 % (17 / 472 base pairs), while there is no difference in LSU and one base pair difference in tef 1 - α and rpb 2. Our two isolates are similar to H. guttulatum ( Hyde et al. 2016) in shape, colour and size of conidia (Table 3 ). Although the conidiophores are longer than in previous collections, this might be due to the branching of the conidiophore of the isolates in this study, whereas the previous collections are unbranched. In addition, the location of the denticles is the same. Therefore, based on morphology and phylogenetic analysis, we identified our isolates as H. guttulatum and this is a new record of H. guttulatum on Caryota mitis . Helicoma guttulatum was first introduced on decaying wood from Thailand by Hyde et al. (2016), based on morphology and phylogeny. Tian et al. (2022) reported a new collection of H. guttulatum on decaying wood of an unidentified host from Thailand.

Figures

Figure 3. Helicoma guttulatum (MHZU 23-0166, new host record) a specimen observed b, c colony on decaying Caryota mitis d conidiophores e – j conidiogenous cells, thereinto j with attached conidia k – o conidia p germinated conidium q, r culture on PDA from above and reverse. Scale bars: 50 μm (d); 20 μm (e – j); 10 μm (k – o); 20 μm (p).