Diaporthales » Pseudoplagiostomataceae » Pseudoplagiostoma

Pseudoplagiostoma jasmini

Pseudoplagiostoma jasmini Gomdola, K.D. Hyde & Jayaward., sp. nov.                      

Index Fungorum number: IF 900131, Facesoffungi number: FoF 14104

Etymology: The specific epithet refers to the host genus, Jasminum, from which the species was isolated.

Holotype: MFLU 23-0068

Associated with leaf spots of Jasminum grandiflorum. Leaf spots irregular, pale to medium brown, surrounded by a dark brown to black margin. Sexual morph: Not observed. Asexual morph: Coelomycetous. Conidiomata (145–)150–230(–240) μm diam., (135–)140–200 μm high (= 184 × 171 μm, n = 20), pycnidial, semi-immersed, solitary, scattered, uniloculate, globose to subglobose, pale brown, surrounded with black margin. Conidiomata wall (19–)22–42(–46) μm thick (= 28 μm, n = 15), consisting of 3–4 layers of thick-walled pseudoparenchymatous cells of textura angularis, outer layers dark brown to black, inner layers pale brown to hyaline. Conidiophores indistinct, often reduced to conidiogenous cells. Conidiogenous cells phialidic, (6.8–)7.7–13.7(–15.6) × 1.6–2.4(–3.0) μm (= 10.7 × 2.1 μm, n = 10), hyaline, cylindrical or clavate, guttulate, smooth-walled, proliferating enteroblastically. Conidia (11.8–)14–22 × (5.2–)6.5–11 μm (= 18.5 × 9.5 μm, n = 50), hyaline, guttulate, 0–2-septate, smooth, wall (0.5–)0.6–1.3 μm thick (= 0.8 μm, n  =  50), cylindrical to truncate or ellipsoidal, elongated, reniform, pyriform or obovoid, apex broadly obtuse, tapering towards a slightly curved base, often with a prominent protruding hilum. Appressorium 9.6 × 7.2 μm long, single-celled, sub-ellipsoidal to obovoid or subglobose or irregular-shaped, hyaline.

Culture characteristics: Colonies on MEA reaching approximately 20 mm diam. after 14 days of incubation at 25 °C, immature with white mycelium, elevation flat or raised, becoming aerial dense and olivaceous brown, filamentous with an undulate margin when aged.

Material examined: Thailand, Chiang Mai Province, Doi Inthanon National Park, Kew Mae Pan nature trail, on fallen leaves of Jasminum grandiflorum (Oleaceae), 20 October 2021, D. Gomdola, DG-PSEU (MFLU 23-0068, holotype), ex-type living culture MFLUCC 23-0044.

GenBank accession numbers: ITS = OQ786078, 28S = OQ786079, β-tub = OQ850148 and tef-1α = OQ850145.

Notes: Pseudoplagiostoma jasmini groups with other species of Pseudoplagiostoma and forms a sister clade with P. dipterocarpicola (MFLUCC 21-0142 and MFLUCC 21-0114) with 35% ML-IQ, 32% MP, and 0.95 PP support (Fig 2). The features are congruent with the morphological species concept of Pseudoplagiostoma (Cheewangkoon et al. 2010).

Pseudoplagiostoma jasmini varies substantially in conidial shape (Fig 5). Conidia of P. jasmini are longer than those of P. dipterocarpicola (MFLUCC 21-0142) (Table 1). The conidial length-to-width ratio of P. jasmini is 2.0, whereas that of P. dipterocarpicola is 2.7.

Excluding gaps in our aligned untrimmed dataset, in pairwise nucleotide comparisons of P. jasmini and P. dipterocarpicola (MFLUCC 21-0142), the following differences were observed: 5.76% across ITS (543 nucleotide base pairs, bp), 1.86% across 28S (818 bp), 21.1% across β-tub (448 bp), and 43.7% across tef-1α (164 bp). The inter-species genetic distances (%) grouped according to the PTP result are provided (Table 2).

Based on the guidelines of Chethana et al. (2021), Jayawardena et al. (2021), and Maharachchikumbura et al. (2021) for introducing new species, we describe P. jasmini as a new species. Despite its support values (35% ML-IQ, 32% MP, and 0.95 PP), we establish P. jasmini as a new taxon, considering the formation of one or two septa in the conidia, a feature lacking in all other Pseudoplagiostoma species; all Pseudoplagiostoma spp. have aseptate conidia. Besides morphology and multigene phylogenetic analyses, we included GCPSR and PTP analyses as further evidence to support the distinct species status of Pseudoplagiostoma jasmini.