Pseudochaetosphaeronema bruguierae Apurillo, Phukhams., E. B. G Jones & K. D. Hyde, 2025

Apurillo, Carlo Chris S., Phukhamsakda, Chayanard, Hyde, Kevin D., Thiyagaraja, Vinodhini & Jones, E. B. Gareth, 2025, New fungal genus, three novel species and one new record from mangroves, with reclassification of Melanconiella (Melanconiellaceae) species, MycoKeys 116, pp. 25-52 : 25-52

Pseudochaetosphaeronema bruguierae Apurillo, Phukhams., E. B. G Jones & K. D. Hyde sp. nov.

Fig. 6

Etymology.

Based on the host Bruguiera cylindrica.

Holotype.

MFLU 24-0192 .

Description.

Saprobic on aerial dead branch of Bruguiera cylindrica . Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata 230–400 × 300–370 µm diameter (x ̄ = 344.5 × 339.0 µm, n = 10), dark brown to black, immersed to erumpent, solitary to gregarious, globose to subglobose, without ostiole. Conidiomata wall 22–66 µm, composed of dark brown, thick-walled cells. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 7–10 µm × 1–2.7 µm (x ̄ = 10.2 × 1.7 µm, n = 20), hyaline, cylindrical or ampulliform, monophialidic, smooth. Conidia 5–10 × 2–3 µm (x ̄ = 6.5 × 2.2 µm, n = 30), hyaline to pale brown, fusiform, 2–3 septate, with constriction in the septa, with 26 guttules.

Known distribution.

Thailand.

Culture characteristics.

Conidia germinate in MEA within 24 hours, with germ tubes arising from one end of the conidia. Colonies on MEA grow up to 30 cm after 3 weeks of incubation at room temperature, circular, white, with light green pigment, flat or effuse, entire edge, reverse exhibits a dark green to pale brown pigmentation.

Material examined.

Thailand • Prachuap Khiri Khan Province: Pranburi District , 12°24'48"N, 99°56'51"E, on aerial dead branch of Bruguiera cylindrica ( Rhizophoraceae ), 25 October 2022, Carlo Chris S. Apurillo, P 11601 ( MFLU 24-0192 , holotype), ex-type living culture MFLUCC 24-0515 .

Genbank Numbers.

ITS: PP 989295, LSU: PP 989290, SSU: PP 989296, tef 1 - α: PQ 273803.

Notes.

Based on a combined phylogenetic analysis of ITS, LSU, SSU, and tef 1 - α sequence data, Pseudochaetosphaeronema bruguierae formed a clade with Pseudochaetosphaeronema siamensis , with the latter showing longer branch length. Base pair comparison of ITS and tef 1 - α sequences revealed a 1.8 % and 15 % difference, respectively. The most significant difference between the two closely related species is their conidial morphology. Pseudochaetosphaeronema bruguierae has larger conidia (6.5 × 2.2 µm) which are fusiform, septate, with multiple guttules. In contrast, Pseudochaetosphaeronema siamensis has smaller conidia (3 × 2 µm) which are subglobose to oval without septation ( Jayasiri et al. 2019). Furthermore, the conidiogenous cells of Pseudochaetosphaeronema siamensis are cylindrical with collarettes at the tips, while some appear flask-shaped with no collarettes for Pseudochaetosphaeronema bruguierae ( Jayasiri et al. 2019). The conidiomata of Pseudochaetosphaeronema bruguierae is also larger than that of Pseudochaetosphaeronema siamensis . Pseudochaetosphaeronema bruguierae is similar to Pseudochaetosphaeronema magnoliae but they are phylogenetically distinct, with P. magnoliae forming a sister clade to P. bruguierae and P. siamensis ( De Silva et al. 2022) . Furthermore, P. bruguierae and P. magnoliae have a higher pairwise difference in the ITS sequences (9.3 %). Although the shape of conidiogenous cells and the conidia of P. bruguierae and P. magnoliae are similar, they differ in terms of size, with P. bruguierae having larger conidiogenous cells and smaller conidia. Additionally, the conidia of P. bruguierae are septate with pronounced multiple guttules, which are not observed in the conidia of P. magnoliae . These support the introduction of Pseudochaetosphaeronema bruguierae as a novel species in Pseudochaetosphaeronema following the guidelines of Jeewon and Hyde (2016) and Maharachchikumbura et al. (2021).

Figures

Figure 6. Pseudochaetosphaeronema bruguierae (MFLU 24-0192, holotype). a host b conidiomata on host c section of conidioma d, e conidiogenous cells f – i conidia j culture on MEA (obverse) k culture on MEA (reverse). Scale bars: 500 µm (b); 100 µm (c); 50 µm (d, e); 20 µm (f); 10 µm (g – i).