Gregarithecium bambusicola Y. Feng & Z. Y. Liu, 2024

Feng, Yao, Liu, Zuo-Yi, Chen, Xiao-Fang, Yang, Mi-Lian, Zhang, Zhi-Yuan & Chen, Ya-Ya, 2024, Phylogeny and taxonomy of two new species in Dictyosporiaceae (Pleosporales, Dothideomycetes) from Guizhou, China, MycoKeys 106, pp. 251-264 : 251-264

Gregarithecium bambusicola Y. Feng & Z. Y. Liu sp. nov.

Fig. 2

Etymology.

The epithet refers to the species inhabiting on bamboo.

Holotype.

GZAAS 21-0199 .

Diagnosis.

Saprobic on dead bamboo culms, the surface of the host has a withered spot with a central protrusion. Sexual morph: Ascomata 386–658 × 129–237 μm (av. 487 × 169 μm, n = 10), scattered to gregarious, immersed with only ostiolar necks visible on the host surface or erumpent, globose to hemispherical with flattened base in section. Peridium composed of several layers of hyaline to dark brown cells of textura angularis. Hamathecium comprising dense, hyaline, branched and anastomosed, septate pseudoparaphyses. Asci 75–104 µm × 17–26 µm (av. 91 × 20 μm, n = 10), 8 - spored, cylindrical, fissitunicate, rounded at the apex with a shallow ocular chamber, small stalk at the base. Ascospores 25–27 × 5–7 μm (av. 26 × 6 μm, n = 10), biseriate, fusiform, hyaline, mostly straight, septum and constricted, smooth, guttulate, with a distinct gelatinous sheath. Asexual morph: undetermined.

Culture characteristics.

Ascospores germinating on WA within 12 h. Colonies slow growing on PDA at 25 ° C, reaching 2 cm diam. in 1 week at 25 ° C. Colonies irregular circular, entire edge, white, off-white in reverse.

Material examined.

China, Guizhou Province, Xingyi City , on dead culms of bamboo, 2 May 2019, Yao Feng, XY- 40 (holotype GZAAS 21-0401 , ex-type living culture GZCC 21-1120 ) , ibid., XY- 40 b (isotype GZAAS 21-0401 , living culture GZCC 21-1120 ) .

Notes.

The genus Gregarithecium comprises a single species, G. curvisporum , which was collected from the culms of Sasa sp. ( Tanaka et al. 2015). In this study, two new strains clustered in a single clade with high support value (98 / 1.00), and were closely related to G. curvisporum (Fig. 1 ). Gregarithecium bambusicola resembles the type species in having cylindrical asci and transparent fusiform, guttulate ascospores surrounded by an entire sheath ( Tanaka et al. 2015). However, unlike the curved ascospores observed in G. curvisporum , G. bambusicola has predominantly straight ascospores ( Tanaka et al. 2015). Furthermore, the ascospores of G. curvisporum have three septa after maturation, which is not seen in G. bambusicola ( Tanaka et al. 2015) . In addition, they can be distinguished by their low sequence similarities. In a comparison of LSU, ITS, SSU, and tef 1 - α nucleotides, G. bambusicola (Type strain GZCC 21-0713 ) has 98 %, 87 %, 99 % and 94 % similarity, in LSU (782 / 800 bp, 2 gaps), ITS (420 / 484 bp, 5 gaps), SSU (527 / 534 bp, no gap), and tef 1 - α (780 / 834 bp, no gap), which is different from G. curvisporum (Type strain KT 922).

Figures

Figure 1. Phylogram based on the maximum likelihood (ML) analysis using the LSU, ITS, SSU, and tef 1 - α sequences of Dictyosporiaceae. Bootstrap support values for ML equal to or greater than 75 % and the Bayesian posterior probabilities equal to or higher than 0.95 PP are indicated above the nodes as ML / PP. Ex-type strains are in black bold and the new taxa are highlighted in bold and red.

Figure 2. Morphology of Gregarithecium bambusicola (GZAAS 21-0199, holotype) A, B appearance of ascomata on host C vertical section of ascoma D peridium E pseudoparaphyses F – I asci J – M ascospores. Scale bars: 50 μm (C); 30 μm (D); 20 μm (F – I); 10 μm (E, J-M).