Pseudoberkleasmium chiangraiense X.G. Tian & Tibpromma, 2022

Tian, Xingguo, Tibpromma, Saowaluck, Karunarathna, Samantha C., Dai, Dongqin, Lu, Yongzhong, Mapook, Ausana & Jayawardena, Ruvishika S., 2022, A new species and a new host record of Pseudoberkleasmium (Pseudoberkleasmiaceae, Dothideomycetes) from Cocos nucifera and Zea mays in northern Thailand, Phytotaxa 547 (3), pp. 232-242 : 239

Pseudoberkleasmium chiangraiense X.G. Tian & Tibpromma , sp. nov. ( FIGURE 3 )

Index Fungorum number: IF 558909; Facesoffungi number: FoF 10572

Etymology:— Referring to Chiang Rai Province, Thailand, where the species was first collected.

Holotype: MFLU 21–0291

Saprobic on dead leaves of Cocos nucifera L. Sexual morph Undetermined. Asexual morph Hyphomycetous. Colonies on natural substrate, superficial, in groups, scattered, black, velvety, glistening, with conidia readily liberated when disturbed. Mycelium immersed in the substrate, composed of septate, branched, smooth, hyaline to pale brown hyphae. Conidiophores micronematous, mononematous, hyaline, smooth. Conidiogenous cells 9–13 × 11–13 μm (x̅ = 10.5 × 12.0 μm, n = 20), holoblastic, monoblastic, determinate, terminal, globose to subglobose or cup-shaped, integrated, connected at the base of conidia, smooth, guttulate, hyaline. Conidia 26–30 × 14–17.5 μm (x̅ = 28 × 15.5 μm, n = 50), acrogenous, solitary, ellipsoidal to obovoid, flattened, muriform, smooth-walled, dark brown to black at apical, pale brown at basal, guttulate, usually with a smooth hyaline conidiogenous cell attached.

Culture characteristics:— Conidia germinating on PDA within 12 hr at 25 °C, not sporulating after two months. Surface with hyphal growth, circular, umbonate, fluffy, White at the margin, dark brown to black at the middle; reverse white to pale brown at the margin, black at the middle. Mycelium superficial, circular, partially immersed, hyaline to brown, smooth.

Material examined:— THAILAND, Chiang Rai Province, Muang District, on decaying leaves of Cocos nucifera (Arecaceae) , 8 December 2020, X. G. Tian, C4–1 ( MFLU 21–0291 , holotype), ex-type culture, MFLUCC 21–0154 ; ibid. 16 January 2021, C6–7 ( MFLU 21–0292 , paratype), living culture, MFLUCC 21–0161 ; ibid. C6–23 ( MFLU 21–0293 , paratype), living culture, MFLUCC 21–0162 .

Notes:— In the phylogenetic analyses, our new strains of Pseudoberkleasmium chiangraiense (MFLUCC 21–0154, MFLUCC 21–0161 and MFLUCC 21–0162) clustered as a sister clade to P. chiangmaiense (MFLUCC 17–2088, MFLUCC 17–1809 and MFLU 21–0290) with a 76% ML bootstrap support value ( FIGURE 1 ). Our new isolate Pseudoberkleasmium chiangraiense (MFLUCC 21–0154) resembles P. pandanicola in having micronematous, mononematous conidiophores and muriform, ellipsoidal to obovoid, flattened guttulate conidia. However, our new isolate (MFLUCC 21–0154) differs from P. pandanicola by its conidia that are dark brown to black at the apex and pale brown at the base, while P. pandanicola has brown to olivaceous green conidia ( Tibpromma et al. 2018). Our new isolate Pseudoberkleasmium chiangraiense (MFLUCC 21–0154) morphologically differs from P. chiangmaiense by the colour of conidia (dark brown to black at apical, pale brown at basal vs. yellow to brown) and smaller size (25.5– 30.0 vs. 30–35 μm) ( Hyde et al. 2019). The nucleotide comparisons revealed that the new strain (MFLUCC 21–0154) is different from P. pandanicola (KUMCC 17–0178) in 15/367 bp (4.09%) of the ITS, and 8/848 (0.94%) of the LSU, while, the new strain (MFLUCC 21–0154) is different from P. chiangmaiense (MFLUCC 17–1809 ex-type) in 15/389 bp (3.86%) of the ITS, 6/840 (0.71%) of the LSU, and 49/899 bp (5.45%) of TEF1-α.

Taxa in Pseudoberkleasmium have similar morphological characteristics with Berkleasmium , however, they are distinct in phylogenetic analyses. Berkleasmium nigroapicale and B. sutheppuiense were introduced from Chiang Mai, Thailand, while our new species was collected in Chiang Rai, Thailand that is geographically not too far. However, Berkleasmium nigroapicale and B. sutheppuiense lack molecular data, thus, we compared the morphology of our new species with B. nigroapicale and B. sutheppuiense and found that B. nigroapicale differs from P. chiangraiense in having cylindrical and clavate conidiogenous cells, and broadly clavate conidia ( Bussaban et al. 2001). While, B. sutheppuiense differs from our new species in having cylindrical conidiogenous cells with subglobose and very dark brown conidia ( Bussaban et al. 2001). Thus, we identified the three new isolates as a distinct new species of Pseudoberkleasmium .

Figures

FIGURE 1. RAxML tree based on analyses of combined LSU, SSU, ITS, TEF1-α and RPB2 dataset. The tree is rooted with Lophiostoma crenatum (CBS 629.86) and L. arundinis (CBS 621.86). Bootstrap values for ML ≥ 75% and Bayesian posterior probabilities (PP) ≥ 0.95 are labelled on the nodes. The newly obtained sequences are indicated in red, while type strains are in black/red bold.

FIGURE 3. Pseudoberkleasmium chiangraiense (MFLU 21–0291, holotype). a–c. The appearance of conidiomata on the host substrate. d–g. Conidia with basal cell (arrows indicate micronematous). h. A colony on PDA from above and below. i–l. Conidia (arrows indicate micronematous). m. A germinated conidium. Scale bars: d, e, m = 30 µm, f, g, i–l = 20 µm.