Neohelicosporium guineensis Y. R. Xiong, Manawas. & K. D. Hyde 2024, sp. nov.

Neohelicosporium guineensis Y. R. Xiong, Manawas. & K. D. Hyde sp. nov. Fig. 5 Etymology. Species epithet refers to the host species name “ guineensis ” from which the fungus was isolated. Holotype. MHZU 23-0153. Description. Saprobic on the rotting petiole of Elaeis guineensis. Sexual morph: Not observed. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, effuse, gregarious, brown. Mycelium composed of partly immersed, partly superficial, pale brown, glistening, septate, branched hyphae. Conidiophores 50–160 µm long, 4–6 µm wide (x ̄ = 120 × 5.2 μm, n = 20), macronematous, mononematous, cylindrical, unbranched or branched at apex, straight, septate, pale brown, brown at root part, smooth-walled. Conidiogenous cells 11.5–20 µm long, 3.5–5.5 µm wide (x ̄ = 15.5 × 4.8 μm, n = 20), mono- to polyblastic, integrated, sympodial, terminal or intercalary, cylindrical, yellowish to pale brown, smooth-walled; with denticles, 1.4–2.7 µm long, 1.2–2 µm wide (x ̄ = 1.9 × 1.6 μm, n = 20), arising from the juncture portion of two conidiogenous cells as tooth-like protrusions, mono- to polyblastic, hyaline, smooth-walled. Conidia 16–20 μm diam. (x ̄ = 18 μm, n = 40) and conidial filament 1.8–3 μm wide (x ̄ = 2.4 μm, n = 40), 90–130 μm long (x ̄ = 112.9 μm, n = 40), solitary, mostly pleurogenous, rarely acrogenous, helicoid, rounded at tip, obvious hump and constricted at septa, coiled 2 ½ – 3 ½ times, 11–12 - septate, becoming loose in water, guttulate, hyaline, smooth-walled. Culture characteristics. Conidia germinating on water agar and germ tubes produced from conidia within 12 h. Colonies growing on PDA attaining 3.5 cm diam. after six weeks at 25 ° C, irregular, undulate, umbonate, rough, superficial and partially immersed, white aerial mycelium, deep brown at immersed area; reverse white to deep brown. Material examined. China, Yunnan Province, Xishuangbanna City, an unidentified forest beside National Highway 219 (21 ° 93 ' N, 101 ° 24 ' E, 549.6 m elev.), rotting petiole of the Elaeis guineensis, 5 February 2023, Y. R. Xiong and Li Lu, XG 186 (MHZU 23-0153, holotype); ex-type, ZHKUCC 24-0113, other living culture ZHKUCC 24-0114. Notes. Two isolates from this study formed a separate lineage and clustered with Neohelicosporium hyalosporum and N. ovoideum in the phylogenetic tree with 88 % ML, 78 % MP bootstrap support and 1.00 BIPP bootstrap support. The nucleotide differences excluding gaps between N. guineensis and its phylogenetically related species were checked: N. hyalosporum (GZCC 16-0076) - ITS: 1.56 % (8 / 513 base pairs), LSU: 0.83 % (7 / 840 base pairs), tef 1 - α: 1.32 % (12 / 912 base pairs), rpb 2: 3.63 % (38 / 1045 base pairs); N. ovoideum (GZCC 16-0064) - ITS: 1.50 % (8 / 534 base pairs), LSU: 0.48 % (4 / 826 base pairs), tef 1 - α: 1.21 % (11 / 912 base pairs), rpb 2: 3.16 % (33 / 1045 base pairs). Neohelicosporium guineensis differs from its closely-related species in the size of conidia and conidiophores (Table 3). Neohelicosporium hyalosporum and N. ovoideum are multi-septate and are not constricted at the septa, while N. guineensis are 11–12 - septate and constricted at the septa (Lu et al. 2018 a, b). Neohelicosporium hyalosporum (Lu et al. 2018 a) has multi-denticles in one conidiogenous cell, while N. guineensis, has no more than three denticles (Fig. 5 e, f) in one conidiogenous cell. Furthermore, N. ovoideum (Lu et al. 2018 b) has 1–2 short-connecting cells between conidiophores, while N. guineensis has one long connecting cell (Fig. 5 d, e) which connects conidiophores at the apex. Based on the phylogenetic placement and morphological variations, we introduce N. guineensis as a new species.

Topic: Plant Pathogens and Fungal Diseases
Subfield: Cell Biology
Field: Biochemistry, Genetics and Molecular Biology
Domain: Life Sciences