Pleopunctum megalosporum R. J. Xu, Q. Zhao & Boonmee

Ren, Guang-Cong, Tibpromma, Saowaluck, Dong, Kai-Xuan, Gao, Chen-Xi, Zhang, Chao-Shan, Karunarathna, Samantha C., Elgorban, Abdallah M. & Gui, Heng, 2024, Unveiling fungi associated with Castanopsis woody litter in Yunnan Province, China: Insights into Pleosporales (Dothideomycetes) species, MycoKeys 108, pp. 15-45 : 15-45

Pleopunctum megalosporum R. J. Xu, Q. Zhao & Boonmee Journal of Fungi 9 (5, no. 560): 9 (2023)

Fig. 8

Description.

Saprobic on dead twigs of Castanopsis calathiformis ( Fagaceae ) in terrestrial habitat. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Colonies on host, sporodochial, superficial, light brown, scattered, and punctiform. Mycelium immersed in the substratum, composed of septate, branched, sub hyaline to light brown hyphae. Conidiophores 13–66 × 2.6–4.2 µm (x ̄ = 37.7 × 3.5, n = 20), macronematous, mononematous, hyaline to light brown, cylindrical, unbranched, septate, smooth-walled. Conidiogenous cells 3.9–5.5 × 3.6–4.7 µm (x ̄ = 4.6 × 4 µm, n = 20), monoblastic, terminal, light brown. The conidia are dimorphic, acrogenous, and solitary. α conidia 30–40 × 10–15 µm (x ̄ = 33 × 12.5 µm, n = 30), hyaline to light brown, muriform, oblong to obovate, constricted at septa, slightly obtuse to rounded at apex. β conidia 48–60 × 24–31 µm (x ̄ = 54.7 × 27.3 µm, n = 30), brown, muriform, oval to long elliptical, slightly constricted at septa, often with a hyaline, elliptical to globose, 0 – multiple-basal cells, 12.5–17.6 × 7.7–11 µm (x ̄ = 14.7 × 9.2 µm, n = 20).

Culture characteristics.

Conidia germinated on PDA within 24 h at room temperature (25 ° C). Germ tubes produced from the basal cells of conidia. Colonies on PDA, reaching 30 mm diameter after 2 weeks at 20–25 ° C, mycelia superficial, irregular, slightly umbonate at the center, fimbriate, undulate edge, grey at the margin, grey white at the center, with hyaline, glistening, granular droplets of oil; reverse, atrovirens, notably radially furrowed, golden brown at the margin.

Material examined.

China, Yunnan Province, Lincang (24 ° 5 ' 30 " N, 100 ° 5 ' 33 " E, elevation: 1557.49 m), on dead woody twigs of Castanopsis calathiformis ( Fagaceae ), 12 July 2020, G. C. Ren, LC 62 ( HKAS 134935 ), living culture KUNCC 21-0622 .

Known host, habitats, and distribution.

Cryptocarya acutifolia , freshwater and terrestrial, China ( Xu et al. 2023; this study).

Notes.

Pleopunctum megalosporum was introduced by Xu et al. (2023) from submerged decaying wood in a freshwater stream in China. Our collection (KUMCC 21-0622) resembles P. megalosporum (KUMCC 22-10799) in having sporodochial conidiomata; septate, subhyaline to light brown mycelium; mononematous, cylindrical, light brown conidiophores; monoblastic, terminal, light brown conidiogenous cells and muriform, oval to long elliptical conidia often with a hyaline, elliptical to globose, 0 – multiple-basal cell ( Xu et al. 2023). Multi-loci phylogenetic analyses based on a concatenated SSU, LSU, ITS, tef 1 - α, and rpb 2 sequence dataset show that our new collection (KUNCC 21-0622) clusters with Pleopunctum megalosporum (KUNCC 10785, KUNCC 10442) with strong support (100 % ML and 1.00 BYPP, Fig. 3 ). Sequence comparison for the ITS and tef 1 - α region between our isolate (KUNCC 21-0622) and Pleopunctum megalosporum (KUNCC 10785) showed no significant base pair differences. Therefore, we introduce our collection as the first record of P. megalosporum from Castanopsis calathiformis ( Fagaceae ) in China.

Figures

Figure 3. Phylogram generated from maximum likelihood analysis based on the combined SSU, LSU, ITS, tef 1 - α, and rpb 2 dataset of Phaeoseptaceae species. Related sequences were obtained from Xu et al. (2023). Bootstrap values for ML are equal to or greater than 75 %, and posterior probability values are equal to or greater than 0.95 from the BYPP analysis labelled on the nodes. Strains of the newly described species are in red, while type strains are in bold. The tree is rooted with Angustimassarina acerina (MFLUCC 14-0505) and A. populi (MFLUCC 13-0034).

Figure 8. Pleopunctum megalosporum (HKAS 134935) a host b colonies on the host surface c conidia on substrate d – h, k – p β conidia with basal cells and conidiophores i, j α conidia showing remnant of conidiogenous cells at base q germinated conidium r, s colony on PDA (r = from above, s = from below). Scale bars: 100 μm (c); 30 μm (d – q); 20 mm (s, r).