Rhytidhysteron sichuanensis X.-L. Xu & C.-L. Yang, sp. nov. (Fig. 4) HOLOTYPE. — China. Sichuan Province, Zizhong county, 29°46’28.29”N, 104°49’19.66”E, alt. 316 m, on dead twigs of Citrus maxima (Burm.) Merr. (Rutaceae), 8.VI.2019, collected by X.-L. Xu & C. - L. Yang, XXL201906001 (holo-, SICAU 19-0004), ex-type living culture (SICAUCC 19-0005). ETYMOLOGY. — The specific epithet refers to the place where the fungus was collected. INDEX FUNGORUM. — IF557217. 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), 20.III.2019, collected by X.-L. Xu & C.-L. Yang, YCL201903006 (SICAU 19- 0008), living culture (SICAUCC 19-0009); on dead twigs of Citrus reticulata Blanco ‘Ponkan’ (Rutaceae), 8.VI.2019, XXL201906003 (SICAU 19-0005), living culture (SICAUCC 19-0006); 5.IV.2019, YCL201904001 (SICAU 19-0007), living culture (SICAUCC 19- 0008); 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 & C.-L. Yang, XXL201910003 (SICAU 20-0002), living culture (SICAUCC 20-0002); Ya’an City, Yucheng District, 30°8’7.84”N, 103°3’21.29”E, alt. 907 m, on dead twigs of Lagerstroemia indica L. (Lythraceae), 28.XI.2019, collected by C.-L. Yang, XXL201911005 (SICAU 20-0005), living culture (SICAUCC 20-0005). ADDITIONAL GENBANK NUMBER. — SICAUCC 19-0005: tub 2, MT075592; rpb 2, MT027608. SICAUCC 19-0006: tub 2, MT075593; rpb 2, MT027609. SICAUCC 19-0008: tub 2, MT075595; rpb 2, MT027611. SICAUCC 19-0009: rpb 2, MT027612. SICAUCC 20- 0002: tub 2, MT075587; rpb 2, MT075603. SICAUCC 20-0005: tub 2, MT075590; rpb 2, MT075606. DESCRIPTION Saprobic on decaying woody branches and twigs. Sexual morphology Ascomata 930-2370 µm long × 760-1930 µm wide × 280- 820 µm high (x = 1318 × 1249 × 479 µm, n = 20), apothecioid, carbonaceous, scattered to gregarious, semi-immersed, black, exposed with irregular, oval to circular in outline, reddish brown, or brown to black disc, folded along the margins with perpendicularly striate along the long axis, compressed at the apex. Exciple 60-107 µm wide (x = 80 µm, n = 15), two-layered, outer layer is composed of thick-walled, dark brown to brown cells of textura globulosa, inner layer is composed of thin-walled, hyaline to light brown cells of textura angularis. Hamathecium composed of 1.3-3.2 µm wide at the base, 3.1-4.9 µm wide at swollen tips (n = 20), dense, hyaline, septate pseudoparaphyses, branched and forming a yellow epithecium above the asci, slightly swollen with dense septa at the apex. Hymenium turns blue in Melzer’s reagent, J +. Asci 143-196 × 9.9-13 µm (x = 169 × 12 µm, n = 30), 6-8-spored, bitunicate, clavate to cylindrical, short pedicellate and apically rounded with an ocular chamber, J- in Melzer’s reagent. Ascospores 18-30 × 8-11 µm (x = 24 × 9.6 µm, n = 40), partially overlapping, uniseriate, 1-2-3-septate, frequently 3-septate, ellipsoid or fusoid, straight or slightly curved, constricted septum, olive-green to brown or 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 3 cm diam after six days at 25°C, flat, circular, initially white, becoming gray to dark gray or reddish brown. NOTES The new species Rhytidhysteron sichuanensis X.-L. Xu & C.-L. Yang, sp. nov. differs from R. thailandium in size of ascomata (930-2370 × 760-1930 × 280-820 µm vs 700- 1200 × 530-750 × 360-640 µm), the width of exciple (60- 107 µm, vs 72-130 µm), the length of asci (143-196 µm vs 135-160 µm), the ascospore septation (1-2-3-septate vs 3-septate), and the color of ascospore. R. sichuanensis X.-L. Xu & C.-L. Yang, sp. nov. is phylogenetically close to R. thailandicum.We compared the nucleotides of LSU, SSU, tef- 1 α and ITS gene regions to R. thailandicum (holo-, MFLUCC 14-0503). R. sichuanensis X.-L. Xu & C.-L. Yang, sp. nov. has 20 (tef- 1 α, 2.15 %), 11 (ITS, 2.16 %) base-pair differences to R. thailandicum.

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 pages 70-72, DOI: 10.5252/cryptogamie-mycologie2022v43a3, http://zenodo.org/record/7815283