Rhytidhysteron subrufulum X. - L. Xu & C. - L. Yang, sp. nov.
Creators: name: Xu, Xiu-Lan
name: Xiao, Qian-Gang
name: Yang, Chun-Lin
name: Jeewon, Rajesh
name: Liu, Ying-Gao
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Fungi
Ascomycota
Dothideomycetes
Patellariales
Patellariaceae
Rhytidhysteron
Rhytidhysteron subrufulum

description: Rhytidhysteron subrufulum X.-L. Xu & C.-L. Yang, sp. nov.
(Fig. 5)
HOLOTYPE. — China. Sichuan Province, Chengdu City, Wenjiang District, 30°42’18.89”N, 103°51’30.42”E, alt. 545 m, on dead twigs of Osmanthus fragrans (Thunb.) Loureiro (Oleaceae), 12.X.2019, collected by C.-L.Yang, YCL201910001 (holo-, SICAU 19-0010), ex-type living culture (SICAUCC 19-0011).
ETYMOLOGY. — The specific epithet refers to the allied species of R. rufulum.
INDEX FUNGORUM. — IF557216.
ADDITIONAL SPECIMENS EXAMINED. — China. Sichuan Province, Zizhong County, 29°46’28.29”N, 104°49’19.66”E, alt. 316 m, on dead twigs of Citrus reticulata Blanco (Rutaceae), 8.III.2019, collected by X.-L. Xu & C.-L. Yang, YCL201903011 (SICAU 19-0009), living culture (SICAUCC 19-0010); 29°46’22.97”N, 104°49’12.20”E, alt. 303 m, on dead twigs of Broussonetia papyrifera (Linnaeus) L’Heritier ex Ventenat (Moraceae), 19.X.2019, collected by X.-L. Xu and C.-L. Yang, XXL201910004 (SICAU 20-0003), living culture (SICAUCC 20-0003); Chongzhou City, 30°33’25.37”N, 103°39’30.67”E, alt. 511 m, on dead twigs of Robinia pseudoacacia L. (Fabaceae), 29.XI.2019, collected by C.-L. Yang, XXL201911012 (SICAU 20-0006), living culture (SICAUCC 20-0006); on dead twigs of Carya illinoinensis (Wangenheim) K. Koch (Juglandaceae), 18.IX.2020, collected by X.-L. Xu, XXL202009001 (SICAU 20- 0011), living culture (SICAUCC 20-0011); Chengdu City, Wenjiang District, 30°42’18.89”N, 103°51’30.42”E, alt. 545 m, on dead wood of Chimonanthus praecox (L.) Link (Calycanthaceae), 6.XI.2020, collected by X.-L. Xu, XXL202011001 (SICAU 22-0001), living culture (SICAUCC 22-0001).
ADDITIONAL GENBANK NUMBER. — SICAUCC 19-0011: tub 2, MT075597; rpb 2, MT027614. SICAUCC 19-0010: tub 2, MT075596; rpb 2, MT027613. SICAUCC 20-0003: tub 2, MT075588; rpb 2, MT075604. SICAUCC 20-0006: tub 2, MT075591; rpb 2, MT075607. SICAUCC 20-0011: tub 2, MW219742; rpb 2, MW219741. SICAUCC 22-0001: tub 2, OM371084; rpb 2, OM371083.
DESCRIPTION
Saprobic on decaying woody branches and twigs.
Sexual morphology
Ascomata 900-2870 µm long × 900-1720 wide × 470-660 high (x = 1909 × 1220 × 546 µm, n = 20), apothecioid, carbonaceous, scattered to gregarious, black, labiates and elliptic or irregular in shape, perpendicularly striate along the long axis, reddish brown to black on the disc. Exciple 36-83 µm wide (x = 62, n = 15), two-layered, outer layer comprising thick- walled, brown to hyaline cells of textura angularis and textura globulosa, inner layer comprising thinwalled, light brown to hyaline cells of textura angularis and textura prismatica. Hamathecium composed of 1.6-2.4 µm wide at the base, 2.5-4.0 µm wide at swollen tips (n = 20), dense, septate, pseudoparaphyses, branched and forming brown epithecium above the asci, slightly swollen at the apex, hymenium turns blue in Melzer’s reagent, J +. Asci 183- 214 × 13-20 µm (x = 202 × 16 µm, n = 15), (5-)8-spored, bitunicate, clavate to cylindrical, with short pedicel and apically rounded with an ocular chamber, J- in Melzer’s reagent. Ascospores 29-41 × 10-15 µm (x = 33 × 13 µm, n = 30), ellipsoidal or fusiform, straight or slightly curved, slightly pointed at both ends, partially overlapping, uniseriate, (2-)3-septate, constricted septum, light brown to dark brown, without a mucilaginous sheath.
Asexual morphology
Undetermined.
Culture characteristics
Ascospores germinating on PDA within 24 hours and germ tubes produced from any cell. Colonies growing on PDA reach 4 cm diam after five days at 25°C, flat, circular, initially white, gradually becoming yellow to gray.
NOTES
Morphological comparison shows R. subrufulum X.-L. Xu & C.-L. Yang, sp. nov. with similar perpendicular striations as typical R. rufulum and R. esperanzae. But the exciple of R. subrufulum X.-L. Xu & C.-L. Yang, sp. nov. (36-83 µm) is thinner than R. rufulum (75-228 µm) and R. esperanzae (60-220 µm), and the asci are wider than R. rufulum (16 µm vs 13.5 µm), and shorter than R. esperanzae (183-214 µm vs 250-270 µm). Furthermore, the asci are (5-)8-spored in R. subrufulum X.-L. Xu & C.-L. Yang, sp. nov., 8-spored in R. rufulum and undescribed in R. esperanzae. And ascospores of R. subrufulum X.-L. Xu & C.-L. Yang, sp. nov. are larger than R. rufulum, but smaller than R. esperanzae (33 × 13 µm vs 31 × 11 µm vs 45 × 17 µm) (Thambugala et al. 2016; Cobos-Villagrán et al. 2021). It is worth mentioning that the specimen SICAU 19-0009 had a large number of fusiform and 1-septate ascospores obviously pointed at both ends, but those ascospores did not germinate at room temperature for a week. The LSU and SSU DNA sequences between R. subrufulum X.-L. Xu & C.-L. Yang, sp. nov. (SICAUCC 19-0011) and R. rufulum (MFLUCC 14-0577, MFLUCC 12-0013) are almost identical, but there are sufficient basepair differences in tef- 1 α (1.66 %, MFLUCC 14-0577) (no data, MFLUCC 12-0013) and ITS (1.47 %, MFLUCC 14-0577) (1.52 %, MFLUCC 12-0013) gene. In the comparison of tef- 1 α sequence, it shows 1.68 % differences between R. subrufulum X.-L. Xu & C.-L. Yang, sp. nov. and R. esperanzae, whereas no data on ITS sequence. With these morphological and DNA sequence differences, this species is identified as a new species named R. subrufulum X.-L. Xu & C.-L. Yang, sp. nov. A table summarizing major morphological differences among Rhytidhysteron species is shown in Table 2.
description: Published as part of Xu, Xiu-Lan, Xiao, Qian-Gang, Yang, Chun-Lin, Jeewon, Rajesh & Liu, Ying-Gao, 2022, Multigene phylogenetic support for novel Rhytidhysteron Speg. species (Hysteriaceae) from Sichuan Province, China, pp. 63-79 in Cryptogamie, Mycologie 20 (3) on page 72, DOI: 10.5252/cryptogamie-mycologie2022v43a3, http://zenodo.org/record/7815283