Pseudorobillarda sichuanensis J.Y. Song & Jian K. Liu

Song, Jing-Yi, Tian, Qing & Liu, Jian-Kui, 2022, Pseudorobillarda sichuanensis sp. nov. associated with Bambusa sp. from Sichuan province, China, Phytotaxa 561 (3), pp. 256-266 : 259-261

Pseudorobillarda sichuanensis J.Y. Song & Jian K. Liu , sp. nov.

MycoBank: MB844119; FIGURE 2

Etymology: In reference to the location where the fungus was collected, Sichuan Province, China.

Holotype: HKAS 124018

Saprobic on a dead culm of Bambusa sp. in terrestrial habitat. Forming black, lenticular spots on the host surface, with Conidiomata breaking through raised cracks with a black center. teleomorph: Undetermined. anamorph: Conidiomata 170–320 μm diam. × 100–180 μm high (x = 237 × 128 μm; n = 10), pycnidial, scattered, immersed to slightly erumpent, multilocular or unilocular, forming a slit-like opening at the apex, black, glabrous, ostiolate. Ostiole in the center of the pileus, circular, dark brown, ostiolar canal filled with hyaline cells, non-papillate. Conidiomatal wall 9–16 μm diam. (x = 12.5 μm; n = 10), multi-layered, composed of thick-walled, hyaline to brown cells of textura angularis or textura prismatica. Conidiophores arising all around the cavity of the conidiomata, reduced to conidiogenous cells, mixed with paraphyses and embedded in a mucilage matrix. Paraphyses 24.5–66 μm long × 1.5–2.5 μm wide (x = 39.5 × 2 μm; n = 20), hyaline, unbranched, narrowly cylindrical to filiform, 1-septate, smooth-walled. Conidiogenous cells 3–4.5 × 2–3.5 μm (x = 4 × 2.6 μm; n = 20), enteroblastic, phialidic, subcylindrical, hyaline, straight, smoothwalled. Conidia 12–17 × 2.5–4 μm (x = 14.5 × 3.5 μm; n = 30), subcylindrical to naviculate, hyaline, rounded at apex, slightly truncated at the base, aseptate, 1–4-guttulate, smooth-walled, bearing 3–4 unbranched, filiform, attenuated, flexuous apical appendages (11–16 μm long). Mean conidial length/width (L/W) ratio = 4.5 (n = 30).

Culture characteristics: Conidia germinated on PDA in 24 hours. Germ tube produced from two-end of the conidia, without sporulation. Colonies on PDA, reaching 30 mm diam. after seven days at 25 °C, rough, dry, opaque, felty, flat, initially white, gradually becoming light pink in the middle and white at the margin, with regular margin and reverse white.

Material examined: CHINA, Sichuan Province, Chengdu, Science City Mountain Park (30°40.99′ N, 104°08.24′ E), on dead culms of Bambusa sp. (Poaceae) , 10 September 2021, Jingyi Song (HKAS 124018, holotype; HUEST 22.0027, isotype); ex-type living culture CGMCC 3.20951 (= UESTCC 22.0029).

Notes: Pseudorobillarda sichuanensis fits well with the generic concept of Pseudorobillarda by its pycnidial conidiomata, paraphyses, phialidic conidiogenous cells, and subcylindrical conidia with appendages at one end. However, it differs from other species in having subcylindrical to fusiform, aseptate, guttulate conidia with 3–4 apical appendages. A detailed morphological comparison of Pseudorobillarda species is provided in TABLE 2 . Pseudorobillarda sichuanensis (sp. nov.) resembles to P. aquatica , P. bolusanthi , P. camelliae-sinensis , P. eucalypti , P. siamensis , P. sojae and P. texana in having aseptate conidia. While P. eucalypti , P. siamensis and P. sojae are distinguished from P. sichuanensis by the absent of paraphyses. Pseudorobillarda aquatica has larger (25–35 μm), eguttulate conidia, while P. sichuanensis has smaller, guttulate conidia (12–17 μm). Pseudorobillarda sichuanensis resembles P. texana in having similar conidiogenous cells and conidia. However, P. sichuanensis has conidiomata with a circular, non-papillate ostiole, conidia with a rounded apex and slightly truncated base, and shorter apical appendages. While P. texana has conidiomata with oval, beaked ostiole and conidia with both ends rounded ( Plaingam et al. 2005). In addition, the Mean conidial L/W ratio of P. sichuanensis (4.6) is significantly less than P. texana (5.5). The multi-gene (LSU-SSU-ITS- rpb2) phylogenetic analysis suggested that Pseudorobillarda sichuanensis clustered together with P. texana and formed a distinct lineage. In addition, a comparison of the ITS region reveals a 62 bp (base pair) difference (without gaps) between P. sichuanensis and P. texana which provides further evidence to support the establishment of new species.

Figures

FIGURE 2. Pseudorobillarda sichuanensis (HKAS 124018, holotype). a Appearance of Conidiomata on the host surface. b–c Close-up of Conidiomata. d Vertical section of conidioma. e Vertical section through Conidiomatal wall. f Paraphyses. g, h Conidiogenous cells with developing conidia. i–m Conidia with appendages. n Colony from above o Colony from below. Scale bars: d = 50 μm, e, f = 20 μm, g–m = 10 μm.