The specific epithet ‘bulbosapicalis’ refers to the bulbous area of the conidia at the apex.

GZAAS 23-0808.

Saprobic on unidentified decaying wood. Sexual morph: Undetermined. Asexual morph: Colonies on the natural substrate superficial, effuse, gregarious, hairy, black, glistening. Mycelium semi-immersed, on the substrate, pale brown to dark brown. Conidiophores (–47)58–128(–199) μm × 7.5–12.5(–16.5) μm (x̄ = 86.7 × 10.6 μm, n = 15), macronematous, mononematous, solitary, straight or slightly flexuous, cylindrical, unbranched, septate, smooth, brown to dark brown, truncate at the apex and wider at the base. Conidiogenous cells 6–17 μm × 7–10.5 μm (x̄ = 10.6 × 8.6 μm, n = 15), monoblastic, holoblastic, terminal, determinate, proliferating, cylindrical, brown to dark brown. Conidia 118–236.5 μm × 15–27 μm (x̄ = 174.8 × 21 μm, n = 30), solitary, acrogenous, cylindrical, ovoid to obclavate, rostrate, smooth, straight or slightly curved, 8–13-septate, slightly constricted at the septa, olivaceous to reddish-brown to dark brown, bulbous at the apex and/or third or fourth cell, truncate at the base, with a spherical hyaline mucilaginous sheath.

Conidia germinating on PDA within 24 hours, producing germ tubes from the apex. Colonies displayed a circular morphology with an umbonate elevation, dense growth and a filiform margin. The surface appeared greyish-green, occasionally exhibiting paler mycelium in the bulge region. The reverse colonies exhibited a circular shape with a filiform margin, displaying a dark brown colour, becoming olivaceous towards the periphery.

China • Hainan Province, Jianfengling National Forest Park, saprobic on unidentified decaying wood, 23 August 2021, Zili Li, JBT04 (GZAAS 23-0808, holotype), ex-type living culture GZCC 23-0732.

Kirschsteiniotheliabulbosapicalis exhibits sporidesmium-like characteristics and shares similar morphologies with other Kirschsteiniothelia species. However, K.bulbosapicalis can be distinguished from other Kirschsteiniothelia species in having different sizes of conidiophores, conidiogenous cells and the unique feature of its conidia, which comprises one or two bulbous structures at or near the apex, with a spherical hyaline mucilaginous sheath. Phylogenetically, K.bulbosapicalis is sister to K.dujuanhuensis (KUNCC 22-12671) with 85% ML and 0.99 PP support (Fig. 1). Similar to our new species, K.dujuanhuensis also comprises a spherical hyaline mucilaginous sheath. Kirschsteiniotheliabulbosapicalis is characterised by larger conidiophores [(–47)58.5–128(–199) μm × 7.5–12.5(–16.5) μm, L/W ratio = 8.2] compared to K.dujuanhuensis [29–74(–119) × 9–11 μm, L/W ratio = 5.1] and larger conidia (118–236.5 μm × 15–27 μm, L/W ratio = 8.3) compared to K.dujuanhuensis [(114–)122–155(–170) × 10–13(–16) μm, L/W ratio = 11.5]. In addition, K.bulbosapicalis exhibits cylindrical to ovoid or obclavate conidia with 8–13 septa and often consist of bulbous structures at the apex and/or the third or fourth cell, as well as a spherical hyaline mucilaginous sheath. In contrast, K.dujuanhuensis typically contains obclavate to subcylindrical conidia that are 6–15 septate.

In addition, the comparison of the nucleotides between the sequences of K.bulbosapicalis and K.dujuanhuensis showed differences of 9% (47/512 bp) across ITS, 1% (8/812 bp) across LSU and 0.1% (2/1003 bp) across SSU, excluding gaps. Based on these findings, we introduce K.bulbosapicalis as a novel species, in accordance with the guidelines established by Jeewon and Hyde (2016) and Maharachchikumbura et al. (2021).