Rhytidhysteron neorufulum Thambug. & K.D. Hyde

Senwanna, Chanokned, Suwannarach, Nakarin, Phookamsak, Rungtiwa, Kumla, Jaturong & Hongsanan, Sinang, 2023, New host and geographical records of Rhytidhysteron in northern Thailand, and species synonymization, Phytotaxa 601 (2), pp. 157-173 : 164-165

Rhytidhysteron neorufulum Thambug. & K.D. Hyde , in Thambugala et al., Cryptog. Mycol. 37(1): 110 (2016)

FIGURE 3

Saprobic on dead twig of Rosa × damascena . Sexual morph: Ascomata 660–1415 µm long, 325–670 µm wide, 200– 490 µm high (x = 935 × 429 × 351 µm, n = 11), hysterothecial when young, becoming irregularly apothecioid when mature, superficial or slightly erumpent from the substrate, coriaceous, scattered, lenticular to Y-shaped, or irregular in shape, with a prominent longitudinal slit, closed at first and opening at maturity, dark brown to black with dark yellow at the center, standing by a short stalk. Exciple 33–85(–106) µm wide, composed of cells of textura angularis, an outer layer pale brown to brown, thick-walled, an inner layer hyaline, thin-walled, continuous to the base (hypothecium). Hamathecium comprising 1.5–3 µm wide, numerous, filiform, septate, branching pseudoparaphyses, fused and slightly swollen at the apex, enclosed in a gelatinous matrix, forming yellowish brown to reddish brown epithecium above the asci. Asci 160–198 × 11.5–16.5 µm (x = 177 × 14 µm, n = 16), 5–8-spored, bitunicate, cylindrical, straight or slightly curved, pedicellate, rounded at the apex, with an ocular chamber. Ascospores (20–)25–32 × (6–)9–13 µm (x = 28.2 × 10.7 µm, n = 47), uniseriate, slightly overlapping, hyaline to brown when immature, becoming dark brown when mature, ellipsoidal to broadly fusiform, rounded to slightly pointed at both ends, 1-septate when immature, becoming 3-euseptate when mature, slightly constricted at the central septum, straight or slightly curved, smooth-walled. Asexual morph: Undetermined.

Culture characteristics:— Ascospores germinating on PDA within 24 hours at room temperature and produced germ tubes from the end of ascospores. Colonies on PDA circular, medium dense, slightly raised, surface smooth, edge entire, velvety to fluffy, initially white, becoming grey-light brown with white margin; not producing pigment on agar.

Material examined:— THAILAND, Chiang Mai Province, Muang District, on a dead twig of Rosa × damascena (Rosaceae) , 10 October 2022, S. Hongsanan, RS01.1 ( CMUB 4002), living culture SDBR-CMU474.

Host and distribution:— Bursera sp. ( Burseraceae , Mexico; Cobos-Villagrán et al. 2020), Elaeagnus sarmentosa ( Elaeagnaceae , China; Du et al. 2023), Hevea brasiliensis ( Euphorbiaceae , Thailand; Huanraluek et al. 2020, Senwanna et al. 2021), Rosa × damascena ( Rosaceae , Thailand; this study), Tectona grandis ( Lamiaceae , Thailand; Ren et al. 2022) undetermined hosts ( Brazil; de Almeida et al. 2014, Europe, Ghana; Boehm et al. 2009a), undetermined dead stem ( Thailand; Thambugala et al. 2016)

Notes:— In a BLASTn search, the LSU and ITS sequences showed 100% similarity to Rhytidhysteron neorufulum strain MFLUCC 13-0221 and MFLUCC 17-0370, respectively, while the TEF1 sequences showed 100% similarity to R. neorufulum strain CBS 306.38 (GU349031). Based on the multi-gene analyses, our strain (SDBR-CMU474) clustered with R. neorufulum ( FIGURE 1 ). Base pair comparisons of the ITS region between the type strain of R. neorufulum (MFLUCC 13-0216) and our strain (SDBR-CMU474) revealed less than 1% differences, and the comparison of LSU and TEF1 nucleotide base pairs of these two strains are showed no differences. The morphology of our strain is similar to R. neorufulum described by Thambugala et al. (2016); however, our strain has shorter and wider asci (160–198 × 11.5–16.5 µm vs. 185–220 × 9.5–13 µm), and shorter ascospores (20–32 × 6–13 µm vs. 27–34 × 6.5–12.5 µm) than the original description. Although there is an unstableness of the size of asci and ascospores within the same species, our strain was identified as R. neorufulum based on molecular analysis. This is the first known record of R. neorufulum on Rosa × damascena (Rosaceae) in Thailand.

Figures

FIGURE 1. Phylogenetic tree conducted by maximum likelihood (RAxML) based on analysis of a combined LSU, ITS, SSU, and TEF1 sequence data of Rhytidhysteron species. Bootstrap values for ML equal to or greater than 60% and Bayesian posterior probabilities (PP) equal to or greater than 0.90 are defined as ML/PP above the nodes. The tree is rooted to Gloniopsis calami (MFLUCC 15-0739) and G. praelonga (CBS 112415). The newly generated strains are indicated in blue and the type strains are in black bold.

FIGURE 3. Rhytidhysteron neorufulum (CMUB4002, new host record). a, b Appearance of ascomata on the substrate. c Section through ascoma. d, e Exciple. f, g Psudoparaphyses with branched swollen tips. h Ocular chamber. i–l Asci from different stages. m Germinating ascospore. n Ascospores. Scale bars: b = 1000 µm, c = 200 µm, d–h = 10 µm, i–l = 50 µm, m–n = 20 µm.