Roussoella fusispora W. H. Tian, K. Wu & Maharachch., 2023

Wu, Kai, Tian, Wenhui, Syed, Asad, Elgorban, Abdallah M., Bahkali, Ali H. & Maharachchikumbura, Sajeewa S. N., 2023, Description of two new species of Roussoella (Roussoellaceae, Pleosporales) associated with bamboo from Sichuan Province, China, Phytotaxa 607 (4), pp. 235-248 : 241

Roussoella fusispora W. H. Tian, K. Wu & Maharachch. , sp. nov. ( FIG. 2 )

MycoBank: MB 849136

Etymology: The epithet is from the word “ fusispora ” which refers to the fusiform ascospores.

Description: Saprobic on dead culms of bamboo. Sexual morph: Ascostromata 130–230 μm high, 260–360 μm diam, immersed under a clypeusor epidermis, raised, visible as black dome-shaped on host surface, solitary to gregarious, clustered, with a central ostiole, with minute papilla. Peridium 6–11.3 μm wide, slightly thinner at the base, composed of several brown to dark brown cell layers of textura angularis to textura prismatica. Hamathecium comprising 0.8–1.9 μm broad, dense, septate, trabeculate pseudoparaphyses, embedded in a gelatinous matrix. Asci 50–70 × 4.5–6 μm (x̄ = 60.8 × 5.4 μm, n = 30), 8-spored, bitunicate, cylindrical, short pedicellate, with furcate or knob-like pedicel, apically rounded with indistinct ocular chamber. Ascospores 7–9.5 × 2.7–3.8 μm (x = 8.2 × 3.2 μm, n = 30), uni-seriate, ellipsoidal to fusiform, with rounded to acute ends, hyaline to dark brown, 1-septate, slightly constricted at the septum, rough-walled, with longitudinally ribbed, surrounded by mucilaginous sheath. Asexual morph: the asexual form of this fungus is undetermined.

Culture characters: Colonies on PDA reaching 27 mm diam. in 20 days at 25 °C in the dark, sparse to medium dense, surface rough, irregular shape, woolly at the margin, velvety, raised at the centre, brown in the middle, dark brown at the margin; reverse black, producing dark brown pigments.

Specimen examined: CHINA, Sichuan Province, Chengdu, Nanmuxi , on dead culms of bamboo, 103°6’42’’ E, 30°19’30’’ N, 24 August 2021, WH Tian, 20210824101 ( HKAS 129206 , holotype), ex-type culture UESTCC 23.0135 = CGMCC 3.25140 .

Notes: Multi-gene phylogenetic analyses showed that Roussoella fusispora forms a sister clade to R. neopustulans . A pairwise nucleotide comparison between the two species showed that R. fusispora differs from R. neopustulans in 9/279 bp of ITS (3.2%), 6/819 bp of LSU (0.7%) and 30/874 bp of TEF1 (3.4%). Morphologically R. fusispora is comparable with R. neopustulans in having cylindrical to cylindric-clavate, bitunicate asci and ellipsoidal to fusiform, brown, 2-celled mature ascospores with longitudinal ribs ( Dai et al. 2017). However, R. fusispora differs from R. neopustulans in having smaller asci (52.9–71.3 × 4.3–5.9 μm vs. 75–90 × 5–6 μm) and smaller ascospores (7.2–9.4 × 2.7–3.8 μm vs. 9–12× 3–4 μm) ( Dai et al. 2017).

Figures

FIGURE2.Roussoellafusispora(HKAS129206,holotype).a–cAscostromataonthebamboohostd,eSectionthroughpseudoascostromata f Peridium g–j Asci k Pseudoparaphyses l–q Ascospores r, s Culture characteristics on PDA. Scale bars: d, e 100 μm; f–k 10 μm; l–q 5 μm.