Rhexoacrodictys dematiospora (W. Dong, Doilom & K.D. Hyde) Bagacay & M.S. Calabon, 2025

Bagacay, Jan Felnesh Exe, Canto, Carr Marlo, Opiña, Lilcah Angelique, Nim, James Ariel, Velo, Jasmine, Lopez, Thomas Angelo, Ferriols, Victor Marco Emmanuel N., Sadaba, Resurreccion B. & Calabon, Mark S., 2025, Pleurotheciaceae in Philippine freshwater ecosystems: new records, asexual morph report of Phaeoisaria filiformis, and phylogenetic assessment, Phytotaxa 682 (2), pp. 121-137 : 129

Rhexoacrodictys dematiospora (W. Dong, Doilom & K.D. Hyde) Bagacay & M.S. Calabon , comb. nov.

Index Fungorum number: IF902859

Basionym: Saprodesmium dematiosporum W. Dong, Doilom & K.D. Hyde , Journal of Fungi 7(no. 711): 16 (2021)

Sexual morph: Undetermined. Asexual morph: Descriptions and illustrations refer to Dong et al. (2021)

Distribution:— CHINA ( Dong et al. 2021).

Notes:— Saprodesmium was introduced by Dong et al.(2021) to accommodate a freshwater taxon, S.dematiosporum from China. In this study, a multi-locus phylogenetic analysis positioned S. dematiosporum as the sister taxon to Rhexoacrodictys chiangraiensis with 94% ML support ( Figure 1 ). However, Saprodesmium dematiosporum was not included in the study of Win et al. (2024) when R. chiangraiensis was introduced. Wang et al. (2024) showed that S. dematiosporum clustered within Rhexoacrodictys clade, as a sister taxon to the three strains of R. melanospora (KUNCC 22–12406, KUNCC 22–12411, KUNCC 23–16529). Although Dong et al. (2021) highlighted distinct morphological differences between Rhexoacrodictys and Saprodesmium —specifically rhexolytic dehiscence with macronematous, long cylindrical conidiophores in Rhexoacrodictys , versus schizolytic dehiscence with micronematous, short conidiophores in Saprodesmium —phylogenetic evidence supports the inclusion of S. dematiosporum within Rhexoacrodictys . To prevent phylogenetic inconsistencies, we recommend transferring Saprodesmium to Rhexoacrodictys and synonymized S. dematiosporum under R. dematiosporum . Furthermore, we have emended the generic description of Rhexoacrodictys to incorporate key morphological traits from R. dematiospora .

Rhexoacrodictys erecta (Ellis & Everh.) W.A. Baker & Morgan-Jones, Mycotaxon 82: 99 (2002), FIGURE 3

Basionym: Mystrosporium erectum Ellis & Everh., J. Mycol. 4(6): 53 (1888)

Synonym: Macrosporium erectum (Ellis & Everh.) Pound & Clem., Minn. bot. Stud. 1(Bulletin 9): 657 (1896)

Acrodictys erecta (Ellis & Everh.) M.B. Ellis, Mycol. Pap. 79: 12 (1961)

Saprobic on submerged decaying wood. Sexual morph: Undetermined.Asexual morph: Colonies on the substratum superficial, effuse, hairy or velvety, black. Mycelium mostly immersed, composed of branched, septate, smooth, pale brown hyphae. Conidiophores 32–148 × 2.5–8.0 μm (x̄ = 86.4 × 5.1 μm, n = 30), macronematous, mononematous, erect, straight or flexuous, thick-walled, smooth, yellowish-brown or brown, septate. Conidiogenous cells monoblastic, integrated, terminal. Conidia 17–24 × 12–21 μm (x̄ = 21.5 × 15.7 μm, n = 30), solitary, dry, acrogenous, oval to subglobose, muriform, short; dark brown to black, smooth, narrowly truncate at the base.

Cultural characteristics:— Conidia germinating on PDA within 24 h. Colonies on PDA at room temperature reaching 30–35 mm diam. in three weeks at 25 °C, circular, slightly raised, entire, dry, surface rough, with sparse mycelium after four weeks, grayish brown in top view, reverse black, composed brown to dark brown, septate, smooth hyphae.

Material examined:— Philippines, Iloilo, Calinog, on decaying wood submerged in a freshwater stream, 3 October 2023, J.A. Nim, CALINOG-002-03-001 ( UPVMI 24–0005), living culture UPVMICC 24–0005.

Notes:— UPVMI 24–0005 closely aligns with the generic description of Rhexoacrodictys erecta ( Baker et al. 2002) . In the multi-locus phylogenetic analysis ( FIGURE 1 ), this isolate clustered with other R. erecta strains (HSAUPmyr4622, IFRD 500–016, HSAUPmyr6489) with strong support (100% ML, 1.00 BYPP). Compared to the isolate described by Baker et al. (2002), R. erecta UPVMI 24–0005 exhibits longer conidiophores (32–148 × 2.5–8.0 μm vs. up to 65 × 3.5–7 μm), but smaller conidia (17–24 × 12–21 μm vs. 24–39 × 15–29 μm). In this study, the new collection is identified as R. erecta based on both morphological and phylogenetic analyses. This is the first report of R. erecta from freshwater habitats in the Philippines.

Figures

FIGURE 1. Phylogenetic tree generated from maximum likelihood (ML) analysis based on ITS, RPB2, and TUB2 sequence data for the species from Pleurotheciaceae. Bootstrap support values for maximum likelihood (ML) higher than 75% and Bayesian posterior probabilities (BYPP) greater than 0.90 are indicated above the nodes in this order. The new isolates are represented in blue. The ex-type strains are indicated in bold. The tree is rooted to Conioscypha hoehnelii (FMR 11592) and C. pleiomorpha (FMR 13134). Bar = 0.09 estimated number of nucleotide substitutions per site per branch.

FIGURE 3. Rhexoacrodictys erecta (UPVMI 24–0005, new record) a host. b,c colonies on wood d–i conidiophores with conidia j–o conidia. Scale bars: a = 20 mm; b, c = 100 μm; d = 50 μm; e–i = 20 μm; j–o = 10 μm.