Ochronectria thailandica Q. J. Shang & K. D. Hyde

Hittanadurage Silva, Veenavee S., Jayawardena, Ruvishika S., Perera, Rekhani H., Li, Qirui & Hyde, Kevin D., 2025, Introducing Muciflexus inthanonensis gen. et sp. nov. and updates on Ochronectria (Hypocreales): New insights from leaf litter fungi in Doi Inthanon National Park, Northern Thailand, MycoKeys 117, pp. 67-88 : 67-88

Ochronectria thailandica Q. J. Shang & K. D. Hyde

Fig. 3

Description.

Sexual morph: see Li et al. (2016). Asexual morph: saprobic and hyphomycetous. Colonies on the host solitary to gregarious, vegetative mycelium superficial. Conidiophores erect, mononematous, smooth, hyaline, unbranched, 2 - septate, 70–89 (x ̄ = 77, n = 9) µm. Conidiogenous cell elongated, hyaline, holoblastic, apically producing monoblastic conidia, 22–37 (x ̄ = 28, n = 9) µm. Conidia hyaline, smooth-walled, aseptate, ellipsoidal to cylindrical rarely ovoid, 4.5–8.5 × 2–3 (x ̄ = 6–2.5, n = 40) µm, L / W 2.5.

Culture characteristics.

Conidia germinating on MEA within 24 hours. Colonies on MEA reaching 1.4 mm diam. within 6 days in the dark at 25 ° C, edge entire, flat or effuse, sparse. After 7 days colonies become white on the front face, and from below, reddish yellow gradually becomes slightly dark when mature.

Material examined.

Thailand • Chiang Mai Province, Doi Inthanon National Park , on a petiole of a fallen broadleaf species, 30 November 2022, Veenavee Silva, V 054 a, MFLU 24–0383 , MFULCC 24–0503

GenBank accession numbers.

ITS: PQ 454717, LSU: PQ 454721

In the phylogenetic analysis, the dataset consisted of 36 strains from Bionectriaceae , with two taxa from Stromatonectriaceae ( CBS 125579 and CBS 127387 ) serving as the outgroup. The final concatenated nucleotide alignment included ITS, LSU, rpb 2, and tef 1 - α sequences, totalling 2854 sites (ITS: 1–514; LSU: 515–1290; rpb 2: 1291–2046; tef 1 – α: 2047–2854). Both maximum likelihood and Bayesian analyses produced similar tree topologies; they were combined in Fig. 4 , using the BI tree as the base. The IQ-TREE web server’s default settings were used for the maximum likelihood tree. At the same time, Tracer v 1.7. 2 was employed to assess the run quality of the BI tree, ensuring effective sampling size (ESS) values for all parameters. The alignment contained 1,096 unique sites (ITS: 262; LSU: 145; rpb 2: 419; tef 1 – α: 270). Although the target species, Ochronectria thailandica , only had ITS and LSU sequences, all four loci were used in the multi-loci phylogenetic analysis, resulting in a stable tree.

Notes.

Ochronectria thailandica was introduced by Li et al. (2016) in Chiang Rai Province, Thailand, from unidentified wood in the water. Our collection from Doi Inthanon includes an isolate found on the petiole of a fallen broadleaf species, which is an asexual morph. In the multi-locus phylogenetic analysis, this isolate clusters with the ex-type strain of Ochronectria thailandica ( MFLUCC 15-0140 ) with BYPP of 1 and MLBS of 100 % support. Based on base pair comparisons, the ITS region is identical (99 %), with two gaps, and the LSU region is also identical (100 %), with no gaps. This confirms that our isolate shares the same identity as the type strain of Ochronectria thailandica . As a result, we introduce the asexual morph of O. thailandica here, supported by graphical illustrations and morpho-phylogenetic evidence. Previously, Ochronectria was recognised as a genus with only a sexual morph, but our discovery establishes its holomorphic nature. Thus, we amend the genus description to include the asexual morph.

Figures

Figure 3. Ochronectria thailandica (MFLU 24–0383) a host (arrow points to the colonies on the petiole) b, c a closer view of the colonies on the host substrate d – f conidiophores with attached conidia g conidia h germinated spore i front and the reverse view of the culture on MEA media. Scale bars: 200 µm (b); 500 µm (c); 20 µm (d – e, h); 5 µm (f); 10 µm (g).

Figure 4. Bayesian inference phylogenetic tree generated from ITS, LSU, rpb 2, and tef 1 – α sequence data for selected taxa from Bionectriaceae. The tree is rooted with two taxa from Stromatonectriaceae (CBS 125579 and CBS 127387). The newly generated sequence is in blue. Holotype and ex-type strains are in bold text. BYPP ≥ 0.95 and MLBS values ≥ 70 % are shown at the nodes.