Pseudoroussoella bidenticola Z. H. Htet, A. Mapook & K. D. Hyde 2024, sp. nov.

Pseudoroussoella bidenticola Z. H. Htet, A. Mapook & K. D. Hyde sp. nov. Fig. 4 Etymology. Name reflects the host plant Bidens pilosa, from which this species was isolated. Holotype. MFLU 24-0266. Description. Saprobic on dead stems of Bidens pilosa. Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata 120–150 × 150–180 µm (av. 126 × 173 µm, n = 5), pycnidial, solitary, immersed to semi-immersed, uni-loculate, brown, globose to subglobose, dark fruiting bodies on the host substrate, without an ostiole. Peridium 10–20 µm wide, comprising 2–3 layers of yellowish brown to brown cells of textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 1–2 μm long, holoblastic, short, globose to subglobose, hyaline and unbranched. Conidia 5–7.5 × 4–5.5 μm (av. 6 × 4.8 µm, n = 20), globose to subglobose, brown to reddish brown, aseptate, thick-walled with a guttule. Culture characteristics. Conidia germinating on MEA within 24 hours, reaching 27 mm after 10 days at 27 ° C, irregular, entire, concentric, opaque, flat, white to pale brown on the surface; concentric, creamy to pale brown in reverse. Material examined. Thailand • Chiang Rai Province, Doi Pui, 19°48'51"N, 99°52'1"E, on dead stems of Bidens pilosa (Asteraceae), 14 March 2023, Zin Hnin Htet (BP-DP-11, MFLU 24-0266, holotype); ex-type culture MFLUCC 24-0273. Notes. In a BLASTn search of GenBank, the closest match for the ITS sequence of our isolate was Roussoella elaeicola strain MFLUCC 15-0276 b (MH 742330) with 94.57 % similarity. The closest match for the LSU region was Pseudoroussoella chromolaenae isolate MFLUCC 17-2062 (MT 394704) with 92.95 % similarity, and the closest match for the SSU region was Parathyridaria tyrrhenica MUT <ITA>: 5371 (KU 314952) with 99.16 % similarity. Additionally, the closest matches for the tef 1 - α and rpb 2 gene regions were Pseudoroussoella elaeicola culture MFLUCC: 17-1483 (MT 235772) and Roussoella sp. strain GMB 1153 (OM 755588) with 97.08 % and 98.27 % similarity, respectively. Pseudoroussoella elaeicola (MFLUCC 17-1483 and MFLUCC 17–2086) was found as a sexual morph in nature (Phookamsak et al. 2019, Mapook et al. 2020); hence, we were unable to directly compare their morphology with our isolate. However, based on comparing the morphology of Pseudorousoella bidenticola (MFLUCC 24-0273) and Ps. chromolaenae (MFLUCC 17-1492), our species differs from Ps. chromolaenae (MFLUCC 17-1492) in having immersed to semi-immersed, globose to subglobose, brown, conidiomata without ostiole, smaller-sized (120–150 × 150–180 µm vs 130–175 (– 230) × 160–230 µm), holoblastic, globose to subglobose conidiogenous cells, and brown to reddish brown, globose to subglobose conidia with guttules, while Ps. chromolaenae (MFLUCC 17-1492) displays superficial, globose to obpyriform, yellowish brown to brown conidiomata with a central ostiole, annellidic, ampulliform to oblong conidiogenous cells, and oblong to oval, conidia that are pale brown to light brown when immature, becoming yellowish brown to reddish brown when mature (Table 4). Based on the multi-locus phylogeny (Fig. 1), our isolate (MFLUCC 24-0273) formed a separate branch related to Pseudoroussoella species with 96 % ML and 1.00 BYPP. When comparing base pair differences between Ps. bidenticola (MFLUCC 24-0273) and Ps. chromolaenae (MFLUCC 17-1492), variations were observed in ITS (3.6 % - 23 / 469), LSU (0.6 % - 5 / 799), SSU (0.6 % - 4 / 630), tef 1 - α (2.6 % - 24 / 891), without gaps. Therefore, we introduced our collection (MFLUCC 24-0273) as a new species based on morphology and multigene phylogeny. Moreover, this is also the first record of Pseudoroussoella species from Bidens pilosa (Asteraceae).