Phaeoacremonium philippinense M.S. Calabon, Bagacay, Nim, Sadaba & E.B.G. Jones sp. nov.,

FIGURE 2 Mycobank number: MB 852555

Etymology:—in reference to Philippines, from where the holotype was collected.

Holotype:—UPVMI 23-0001

Saprobic on decaying wood submerged in freshwater. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Aerial structures in vitro on PDA: Mycelium 1.5–3 μm wide, consisting of branched, septate hyphae that occur singly or in bundles of up to six; hyaline to subhyaline, and smooth. Conidiophores 21–52 × 1.2–1.5 μm (x = 34.9 × 1.4 µm, n = 40), mostly of medium length, usually unbranched, arising from aerial or submerged hyphae, mostly erect, up to 4-septate, often ending in a single terminal phialide, hyaline to subhyaline, smooth. Phialides 1.5–3 × 1–1.5 μm, terminal or lateral, mostly monophialidic, smooth, hyaline to subhyaline, collarettes; type I phialides 3–16 × 0.9–3 µm (x = 8 × 1.4 µm, n = 30), predominate, mostly cylindrical to subcylindrical; type II phialides 8–14 × 1–3 µm (x = 10.7 × 1.8 µm, n = 30), mostly cylindrical, some navicular; type III phialides 18–24 × 1–2.5 µm (20.5 × 2.3 µm, n = 30), cylindrical, subulate. Conidia 2.5–4 × 0.7–1.2 µm (x = 3.6 × 1.1 µm, n = 30) hyaline, oblong-ellipsoidal or oblong, some allantoid. On surface or submerged in the agar: phialides 1.5–19 × 0.9–2.5 µm (7.1 × 2 µm, n = 30), hyaline, mostly cylindrical to subcylindrical. Conidia 2–4 × 0.5–1.2 µm (x = 3.2 × 0.9 µm, n = 30) hyaline, oblong-ellipsoidal to oblong.

Cultural characteristics:—Conidia germinating on PDA within 24 hours. Colonies on PDA reaching 35–40 mm diameter after 25 days at 25˚C. Mycelia superficial, circular, with filiform margin, flat, smooth, transparent, spare, from above gray to dark brown at the center then becoming white to brown at the margin; reverse, grayish brown at the center then becoming light brown to dark brown at the margin.

Material examined:— Philippines. Miagao, Iloilo, Tinagong Dagat lake, on submerged decaying wood of an unidentified plant, 11 March 2023, M.J. Concha, 01-OV-07 (UPVMI 23-0001, holotype), ex-living culture UPVMICC 23-0001. Philippines. Miagao, Iloilo, Tinagong Dagat lake, on submerged decaying wood of an unidentified plant, 11 March 2023, M.J. Concha, 01-OV-08 (UPVMI 23-0002, paratype), ex-paratype living culture UPVMICC 23-0002.

Notes:—Currently, there are four reported species of Phaeoacremonium in freshwater habitats: P. aquaticum (Hu et al. 2012), P. ovale (Huang et al. 2018), P. philippinense (in this study) and P. thailandense (Calabon et al. 2021). Phaeoacremonium philippinense shares the same morphology with other members of the genus, with short, usually unbranched conidiophores, presence of three types of phialides, and oblong-ellipsoidal to oblong conidia. The generic closest match of the sequences based on nucleotide BLAST searches in GenBank is Phaeoacremonium. Phaeoacremonium krajdenii (NCCPF No. 600006) is the closest species based on BLAST result of ITS region with 98.88% similarity. The actin sequence was 98.33% similar to Phaeoacremonium krajdenii (CBS 423.73), while tef1- α sequence was 96.82% similar to Phaeoacremonium minimum (UCRPA7). The multi-locus phylogenetic analyses show that P. philippinense is a distinct species and a sister taxon to P. thailandense with high bootstrap support (100% ML, 1.00 BYPP). Based on the ITS, act, and tef1-α sequence data, P. philippinense differs by 49 (8.06%, 608 bp), 65 (27.54%, 236 bp), and 62 (6.97%, 890 bp) base pairs with P. thailandense, respectively.