Scytinostroma subduriusculum Yue Li, S.L. Liu & S.H. He, 2023

Li, Yue, Xu, Wei-Qi, Liu, Shi-Liang, Yang, Ning & He, Shuang-Hui, 2023, Species diversity and taxonomy of Scytinostroma sensu stricto (Russulales, Basidiomycota) with descriptions of four new species from China, MycoKeys 98, pp. 133-152 : 133

Scytinostroma subduriusculum Yue Li, S.L. Liu & S.H. He sp. nov.

Figs 6 , 7

Type.

China, Beijing, Haidian District , Beijing Botanical Garden , on dead angiosperm branch, 15 July 2022, He 7657 (BJFC 038793, holotype) .

Etymology.

Refers to the morphological similarity and close phylogenetic relationship with S. duriusculum .

Fruiting body.

Basidiomes annual, resupinate, widely effused, closely adnate, inseparable from substrate, membranaceous to coriaceous, first as small patches, later confluent up to 18 cm long, 3 cm wide, up to 160 µm thick in section. Hymenophore smooth, light yellow (4A4) to greyish orange (5B4), 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 pale yellow, distinctly thick-walled, moderately branched, 2.5-4.5 µm in diam., dextriniod, CB+. Catahymenium composed of skeletal hyphae, gloeocystidia, basidia and basidioles. Skeletal hyphae abundant, similar to those in the context, but strongly dextrinoid, 1-1.5 µm in diam. Gloeocystidia abundant, subclavate to subcylindrical, colorless, thin-walled, usually with contents, SA+, 50-70 × 6-9 µm. Basidia subclavate to subcylindrical, slightly curved, thin-walled, colorless, smooth, with four sterigmata and a basal simple septum, 30-45 × 6-7.5 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores subglobose, with a distinct apiculus, thin-walled, colorless, smooth, occasionally with oil-drops, amyloid, CB-, (6-) 6.2-7 (-7.5) × (5.5-) 5.8-6.8 (-7) µm, L = 6.5 µm, W = 6.3 µm, Q = 1.01-1.04 (n = 90/3).

Additional specimens examined.

CHINA, Beijing, Changping District, Baiyanggou Scenic Spot, on dead angiosperm branch, 21 July 2021, He 7134 (BJFC 036451); Daxing District , Nanhaizi Park, on dead angiosperm branch, 31 July 2021, He 7148 (BJFC 036465); Fangshan District , Qinglonghu Park, on dead Sabina branch, 31 July 2021, He 7150 (BJFC 036467); Fengtai District , Yungang Forest Park, on dead Sabina tree, 25 July 2021, He 7141 (BJFC 036458); Haidian District , Bajia Country Park, on Sabina stump, 16 August 2022, He 7717 (BJFC 038853) ; Guangxi Autonomous Region , on dead angiosperm branch, 16 June 2016, He 3819 (BJFC022318) ; Guizhou Province, Libo Country, Xiaoqikong Scenic Spot , on dead angiosperm branch, 16 June 2016, He 3822 (BJFC022321) ; Hainan Province, Baoting Country, Qixianling Forest Park, on dead angiosperm branch, 18 March 2016, He 3590 (BJFC022090) & He 3593 (BJFC022092) ; Haikou City, Jinniuling Park , on dead twig of living Araucaria , 7 June 2016, He 3825 (BJFC022327) ; Wanning City, Xinglong Tropical Botanical Garden , on dead angiosperm branch, 19 March 2016, He 3603 (BJFC022101) ; Yunnan Province, Qiubei Country, Puzhehei Scenic Spot , on dead angiosperm branch, 26 July 2014, He 20140726-5 (BJFC019218) & He 20140726-6 (BJFC019219) ; Ruili City, Moli Tropical Rain Forest Scenic Spot, on fallen angiosperm trunk, 2 December 2015, He 3497 (BJFC021894) . THAILAND, Chiang Rai, Mae Fah Luang University , on fallen angiosperm trunk, 21 July 2016, He 4045 (BJFC023484) ; Krabi, on dead angiosperm branch, 28 July 2016, He 4146 (BJFC023588) . VIETNAM, Ho Chi Minh City Animal and Botanical Garden , on fallen angiosperm trunk, 4 September 2017, He 5204 (BJFC024722) .

Notes.

Scytinostroma subduriusculum is characterized by subcylindrical gloeocystidia, subglobose, relatively large basidiospores, and growth on both angiosperm and gymnosperm trees. It is widely distributed in China, and also found in Thailand and Vietnam. In the phylogenetic tree (Fig. 1 ), S. subduriusculum formed a distinct lineage sister to S. duriusculum (Berk. & Broome) Donk. There are 24 base pair differences between S. subduriusculum (He 4146, Thailand) and S. duriusculum (He 5748, Sri Lanka), and 66 differences between S. subduriusculum and S. duriusculum (CBS 757.81, France) of total 665 base pairs of ITS1+5.8S+ITS2 sequences. The similarities are 96.4% (He 4146 vs. He 5748) and 90.1% (He 4146 vs. CBS 757.81). The French samples may represent an undescribed species because their ITS1+5.8S+ITS2 sequences largely differ from those of Sri Lankan samples (71 differences of total 665 base pairs with only 89.3% similarity). Morphologically, the two species share subclavate to subcylindrical gloeocystidia and subglobose basidiospores. However, S. duriusculum has shorter basidia (20-25 µm) and smaller basidiospores (6-6.5 × 5.5-6 µm, measured from He 5748 from Sri Lanka).

Figures

Figure 1. Phylogenetic tree of ML analysis from the ITS 1 - 5.8 S-ITS 2 - nrLSU sequences of Peniophoraceae taxa. Branches are labelled with likelihood bootstrap values (≥ 50 %, first) and Bayesian posterior probabilities (≥ 0.95, second). New species are set in bold and highlighted.

Figure 6. Basidiomes of Scytinostroma subduriusculum a He 7657 (BJFC 038793, holotype) b He 7134 (BJFC 036451) c He 7141 (BJFC 036458) d He 7148 (BJFC 036465) e He 7150 (BJFC 036467) f He 7717 (BJFC 036467). Scale bars: 1 cm (a-f).

Figure 7. Microscopic structures of Scytinostroma subduriusculum (from the holotype He 7657) a basidiospores b basidia c basidioles d gloeocystidia e skeletal hyphae from hymenium f skeletal hyphae from subiculum. Scale bars: 10 µm (a-f).