Species diversity and taxonomy of Scytinostroma sensu stricto (Russulales, Basidiomycota) with descriptions of four new species from China Author Li, Yue https://orcid.org/0000-0003-4091-1506 School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China Author Xu, Wei-Qi https://orcid.org/0009-0000-5675-386X School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China Author Liu, Shi-Liang https://orcid.org/0000-0001-7556-2575 State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China Author Yang, Ning https://orcid.org/0009-0007-6900-5669 Beijing Municipal Research Institute of Eco-Environmental Protection, Beijing 100037, China Author He, Shuang-Hui https://orcid.org/0000-0003-4702-3034 School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China heshuanghui@bjfu.edu.cn text MycoKeys 2023 2023-06-13 98 133 152 http://dx.doi.org/10.3897/mycokeys.98.105632 journal article http://dx.doi.org/10.3897/mycokeys.98.105632 1314-4049-98-133 9B30833B688B54BABFE577817700CC53 Scytinostroma subrenisporum Yue Li, S.L. Liu & S.H. He sp. nov. Fig. 8 Type . China , Guizhou Province , Libo County , Maolan Nature Reserve , on dead angiosperm branch, 11 July 2017 , He 4792 (BJFC 024311, holotype ) . Figure 8. Scytinostroma subrenisporum (from the holotype He 4792) a basidiomes b basidiospores c basidia d skeletal hyphae from hymenium e skeletal hyphae from subiculum. Scale bars: 1 cm ( a ); 10 µm ( b-e ). Etymology. Refers to the morphological similarity and close phylogenetic relationship with S. renisporum . Fruiting body. Basidiomes annual, resupinate, widely effused, closely adnate, inseparable from substrate, membranaceous to coriaceous, first as small patches, later confluent up to 10 cm long, 2.5 cm wide, up to 100 µm thick in section. Hymenophore smooth, pale orange (5A3), light orange (5A4) to greyish orange [5B(5-6)], unchanged in KOH, not cracked; margin thinning out, adnate, fimbriate, white or concolorous with hymenophore surface. Context pale yellow. Microscopic structures. Hyphal system dimitic. Context thickening, compact. Generative hyphae rare, scattered, simple-septate, colorless, thin-walled, 2-3 µm in diam., IKI-, CB-. Skeletal hyphae dominant, colorless to yellow, distinctly thick-walled, moderately branched, 1.5-2 µm in diam., dextriniod, CB+. Catahymenium composed of skeletal hyphae, basidia and basidioles. Skeletal hyphae abundant, similar to those in the context, but strongly dextrinoid, moderately branched with acute tips, 1.5-2 µm wide at lowest part. Gloeocystidia absent. Basidia subcylindrical, slightly curved, thin-walled, colorless, smooth, with four sterigmata and a basal simple septum, 35-45 x 4.5-6.5 µm ; basidioles in shape similar to basidia, but slightly smaller. Basidiospores ellipsoid to reniform, with a distinct apiculus, thin-walled, colorless, smooth, amyloid, CB-, (5.5-) 6-6.5 (-7) x (3.8-) 4-5 (-5.5) µm , L = 6.2 µm , W = 4.4 µm , Q = 1.35-1.45 (n = 60/2). Additional specimens examined. China , Anhui Province , Qimen County , Guniujiang Nature Reserve , on dead angiosperm branch, 8 August 2013 , He 1720 (BJFC 016187) ; Fujian Province , Wuyishan County , Wuyishan Nature Reserve , on dead angiosperm branch, 3 October 2018 , He 5685 (BJFC 026747) & He 5686 (BJFC 026748) ; Guangxi Autonomous Region , Huanjiang County , Mulun National Nature Reserve , on dead angiosperm branch, 10 July 2017 , He 4751 (BJFC 024270) ; Guizhou Province , Libo County , Maolan Nature Reserve , on angiosperm tree, 15 June 2016 , He 3792 (BJFC 022291) ; Hunan Province , Guzhang County , Gaowangjie National Nature Reserve , on dead angiosperm branch, 3 August 2018 , He 5626 (BJFC 026688) ; Jiangxi Province , Ji'an County , Jinggangshan Scenic Spot , on dead angiosperm branch, 11 August 2016 , He 4303 (BJFC 023745); Lianping County , Jiulianshan Nature Reserve , on dead Liana branch, 14 August 2016 , He 4384 (BJFC 023825); Yifeng County , Guanshan Nature Reserve , on dead angiosperm branch, 9 August 2016 , He 4170 (BJFC 023612) & He 4199 (BJFC 023641) . Notes. Scytinostroma subrenisporum is characterized by the absence of gloeocystidia and ellipsoid to reniform basidiospores. In the phylogenetic tree (Fig. 1 ), S. subrenisporum is closely related to S. acystidiatum and S. renisporum . Scytinostroma acystidiatum that was recently described from China, is similar to S. subrenisporum by sharing the absence of gloeocystidia but differs in having smaller basidiospores (5.2-6 x 3.5-4.5 µm , measured from the type by the authors, Zhang et al. 2023 ). Scytinostroma renisporum is similar to S. subrenisporum by sharing ellipsoid to reniform basidiospores but differs by having cylindrical, subclavate or fusoid gloeocystidia and a distribution in Cote d'Ivoire , western Africa ( Boidin and Lanquetin 1987 ).