Helianthoconium helianthosporum X. Yu. Zhang, Q. Y. Zhang & B. Fan sp. nov.

Fig. 10

Etymology.

Derived from the Latin word “helianthus,” indicating that it is named for distinctive morphology of its conidia, which closely resemble sunflower seeds.

Type.

CHINA • Jiangsu Province, Nanjing, Nanjing Forestry University, Baima Campus, fungal endophyte from Pinus densiflora, May 2023, Ben Fan and Xiuyu Zhang, NF 684 (holotype HMAS 352957, culture ex-type CGMCC 3.28953) .

Description.

Mycelium composed of hyaline, smooth or warty, aseptate, flexuous, branched, slender, 1.2–2.8 μm diam. Asexual state: Conidiophores erect, solitary, arising from hyphae, 2–15 - septate, straight to flexuous, subcylindrical, brown, smooth, stout, unbranched, (57.4 –) 63.3–122.6 (– 161.6) × (2.3 –) 3.1–4.7 (– 4.7) μm. Conidiogenous cells terminal, pale brown to brown, smooth, subcylindrical, terminal, connected in series, (4.2 –) 5.4–10.3 (– 11.9) × (2.7 –) 3.0–3.9 (– 4.1) μm. Conidia terminal and lateral, aseptate, smooth, brown, sunflower seed-shaped, base truncate, (6.0 –) 6.9–8.2 (– 8.5) × (3 –) 3.5–4 (– 5) μm. Sexual state unknown.

Culture characteristics.

Colonies on MEA slow-growing, velvety to hairy, with entire margin; surface dark olivaceous-grey. On SNA and OA, the colonies appear off-white (Fig. 10 A – C). The optimal temperature for growth was 20–25 ° C, reaching 4–5 mm diam after 10 days on MEA. No growth was observed at 5 ° C and 35 ° C.

Additional specimen (paratype) examined.

CHINA • Jiangsu Province, Nanjing, Nanjing Forestry University, Baima Campus, fungal endophyte from Pinus densiflora, May 2023, Ben Fan and Xiuyu Zhang, paratype NF 884 .

Notes.

In the phylogenetic analyses of Capnodiales (Fig. 1) and Dissoconiaceae (Fig. 2), the isolate of Helianthoconium helianthosporum formed a well-supported clade within Dissoconiaceae (ML / BI = 100 / 1.00). BLAST analysis of the ITS sequence of NF 684 against NCBI reveals a 10.78 % (51 / 473 bp) difference from its closest known relative, indicating a clear genetic distinction. Although consistently placed within Dissoconiaceae, Helianthoconium helianthosporum differs from other genera in this family by its sunflower seed-shaped conidia (vs. broadly ellip soidal to globose in Globoramichloridium and cylindrical in Paradissoconium) and shorter conidiogenous cells (4.2–11.9 μm vs. 15–45 μm in Paradissoconium narthecii). Based on these phylogenetic and well-defined morphological differences, we propose the new genus Helianthoconium, with H. helianthosporum as the type species.