Diaporthe thailandica Louangphan, Phukhams., K. D. Hyde & Bhunjun, 2025

Phukhamsakda, Chayanard, Hyde, Kevin D., Samarakoon, Milan C., Louangphan, Johnny, Navasit, Kedsara, Al-Otibi, Fatimah & Bhunjun, Chitrabhanu S., 2025, Unveiling Sordariomycetes taxa associated with woody litter in Northern Thailand, MycoKeys 115, pp. 155-185 : 155-185

Diaporthe thailandica Louangphan, Phukhams., K. D. Hyde & Bhunjun sp. nov.

Figs 3 , 4

Etymology.

The name refers to the country where the holotype was collected.

Holotype.

MFLU 23–0473 .

Description.

Saprobic on decaying dicot, visible as black necks immerging through the host surface. Sexual morph: Ascomata 328–495 × 303–371 µm (x ̄ = 400 × 343 µm, n = 10), immersed in the host epidermis, globose to sub-globose, solitary or occur in clusters, black, ostiolate, papillate. Ostiole neck 220 × 86 µm, long, filled with periphysate. Peridium 20–50 µm wide, composed of several layers of cells of textura angularis, outer layers dark brown and inner layers hyaline to brown, thin-walled. Paraphyses 3.2–6.6 µm (n = 20), thin-walled, 2–4 - septate, hyaline, wide at base, tapering towards the apex. Asci 45–58.9 × 8.6–12.7 µm (x ̄ = 51.5 × 10.5 µm, n = 40), unitunicate, 8 - spored, clavate to subclavate, straight to slightly curved, sessile, with a J-, apical ring. Ascospores 11–15.5 × 3.9–5.6 µm (x ̄ = 13.5 × 4.7 µm, n = 40) L / W = 2.8, overlapping uniseriate to biseriate, 1 - septate, constricted at the septum, ellipsoidal, smooth-walled, 2–4 - guttulate, straight, hyaline, without appendages or a mucilaginous sheath. Asexual morph on PDA: Conidiomata 500–700 × 300–600 µm (x ̄ = 580 × 480 µm, n = 10), pycnidial, scattered or aggregated, globose or variable in shape, ostiolate with prominent neck, dark brown to black, pycnidal wall brown, consisting of thick-walled cells of textura angularis, conidial mass globose, initially hyaline to yellowish, becoming white to cream, conidial droplets exuding from central ostioles. Conidiophores 10–29.5 × 1.3–2.5 μm (x ̄ = 16.9 × 1.9 µm, n = 40), ampulliform to subcylindrical, filiform, branched to unbranched, 1–3 - septate, hyaline, smooth, straight or slightly curved, wider at base, tapering towards the apex. Conidiogenous cells 2.1–8.1 × 1–2.3 μm (x ̄ = 4.2 × 1.5 µm, n = 40), subcylindrical, filiform, straight to curved, tapering towards the apex, collarette not flared, hyaline. Alpha conidia 5.3–8.8 × 2.3–3.5 μm (x ̄ = 7.3 × 2.9 μm, n = 40), ellipsoid, apex bluntly rounded, base obtuse to subtruncate, smooth, hyaline, bi- to multi-guttulate. Beta conidia 8.5–18.5 × 1.2–2 μm (x ̄ = 13.3 × 1.7 μm, n = 40), filiform, flexible to slightly curved, hyaline, base subtruncate, and aseptate. Gamma conidia not observed.

Culture characteristics.

Colonies on PDA, reaching 40 mm diam., after 2 weeks at 25 ° C, initially white, turning pale brown after 7–10 days, radiating to the edge, margin undulate, medium dense, flat or umbonate; reverse, cream, radiating white outwardly with grey patches.

Material examined.

Thailand, Chiang Rai Province, Muang District , on a dead unidentified dicot, 16 January 2023, J. Louangphan, CR 1-09 ( MFLU 23–0473 , holotype); ex-type MFLUCC 24–0523 = MFLUCC 23–0299 .

Host.

Unidentified branch (this study).

Distribution.

Thailand (this study).

Notes.

Diaporthe thailandica ( MFLUCC 23-0299 and MFLUCC 24–0523 ) formed a sister clade with isolates of D. raonikayaporum ( CBS 133182, MFLUCC 14–1133 , and MFLUCC 14–1136 ) with 100 % ML / 1.00 BPP support (Fig. 1 ). Diaporthe thailandica differs from D. raonikayaporum in its conidiomata (500–700 × 300–600 µm vs. 110–200 × 50–130 μm), conidiophores (10–29.5 × 1.3–2.5 μm vs. 16–26 × 2–3 μm), conidiogenous cells (2.1–8.1 × 1–2.3 μm vs. 5–10 × 2–3 μm), and beta conidia (8.5–18.5 vs. 7–13 μm) ( Gomes et al. 2013). Diaporthe thailandica differs from D. raonikayaporum (= D. neoraonikayaporum MFLUCC 14–1133 ) in its conidiomata (500–700 × 300–600 µm vs. 690–1190 × 805–1285 μm), conidiophores (10–29.5 μm vs. 15–23 μm), alpha conidia (5.3–8.8 × 2.3–3.5 μm vs. 4–6 × 2–3 μm), and beta conidia (8.5–18.5 μm vs. 13–21 μm) ( Doilom et al. 2017). Gamma conidia was observed in D. raonikayaporum (= D. neoraonikayaporum ) but not in D. thailandica ( Doilom et al. 2017). Diaporthe thailandica further differs from D. raonikayaporum , which has only been reported as an asexual morph ( Gomes et al. 2013; Doilom et al. 2017). Our strain differs significantly (> 2.5 %) compared to the sequence data of D. raonikayaporum (Table 3 ). However, our isolate does not have cal sequence data, while his 3 sequence data is not available for D. raonikayaporum ( MFLUCC 14–1133 and MFLUCC 14–1136 ). A pairwise homoplasy index showed Φw = 1.0 when a genealogical correlation model was applied between Diaporthe thailandica and D. raonikayaporum (Fig. 5 ). Thus, Diaporthe thailandica is reported as a new species based on morphology and molecular evidence.

Figures

Figure 1. Phylogram of the Diaporthe sojae species complex generated from a maximum likelihood analysis based on the combined ITS, tef 1, tub 2, cal, and his 3 sequence data. Diaporthella corylina (CBS 121124) was used as the outgroup. Bootstrap support values ≥ 60 % ML / ≥ 0.90 BPP are given at the nodes. The newly generated taxa are indicated in red. The holotype / ex-type strains are denoted with T.

Figure 3. Diaporthe thailandica (MFLU 23–0473, holotype) a host substrate b, c ascomata on host substrate d vertical section through ascoma e peridium f ostiole g hamathecium h – j asci k – n ascospores o a germinated ascospore p front and reverse view of the colony on PDA. Scale bars: 200 μm (b); 100 μm (c, d); 20 μm (e – j); 10 μm (k – o).

Figure 4. Diaporthe thailandica (Asexual morph, MFLUCC 24–0523) a culture on pda b, c conidiomata sporulating on pda d, e conidiogenous cells giving rise to conidia f alpha conidia g beta conidia h alpha and beta conidia. Scale bars: 500 µm (b, c); 10 µm (d – h).

Figure 5. The splits graph from the pairwise homoplasy index (PHI) test generated from the combined ITS, tef 1, tub 2, cal, and his 3 sequence data of Diaporthe thailandica (indicated in red) and closely related taxa using both LogDet transformation and splits decomposition. PHI test results (Φw) < 0.05 indicate significant recombination within the dataset.