Choiromyces cerebriformis T. J. Yuan, S. H. Li & Y. Wang, 2021

Yuan, Tian-Jun, Raspé, Olivier, Li, Yong-Jun, Wang, Li, Su, Kai-Mei, Wang, Yun, Su, Hong-Yan, Xiong, Hai-Kuang & Li, Shu-Hong, 2021, Choiromyces cerebriformis (Tuberaceae), a new hypogeous species from Yunnan, China, Phytotaxa 482 (3), pp. 251-260 : 256

Choiromyces cerebriformis T. J. Yuan, S. H. Li & Y. Wang , sp. nov. Fig. 2a–f

MycoBank: MB837904.

Diagnosis: Choiromyces cerebriformis differs from similar species in having ascomata up to 10 cm in diameter, with larger and deeper lobes and light orange-brown gleba.

Holotype: CHINA, Yunnan Province, Diqing Autonomous Prefecture, Shangri-La County, Three dam township, Haba village, 27°21’6.3647”N, 100°06’ 34.6895”E, elevation 4005 m, under Abies delavayi Franch. and Rhododendron simsii Planch. in mixed evergreen hill forest, with soil types mainly red and brown soils, 24 Sep. 2020, collected by X. H. Wang ( KUN-HKAS 107566, holotype; YAAS 8890, isotype).

Etymology: cerebriformis refers to the aspect of ascomata which looks like a brain.

Ascomata hypogeous, up to 10 cm in diam, knobby, with deep lobes; surface glabrous, whitish when young, then pale yellow to reddish-brown with dark spots at maturity ( Fig. 2b, c ). Peridium 210–280 µm thick, plectenchymatous, with two layers, the outer layer 60–80 µm thick, reddish-brown, the inner layer 150–200 µm thick, hyaline with larger cells (25–40 µm diam, wall 0.5–2.0 µm thick; Fig. 2d ). Gleba ( Fig. 2d, e ) solid, labyrinthoid, light orange-brown, marbled with greyish white veins. Odor strong, pleasant. Asci hyaline, clavate to sac-like, 8-spored, (75–)75–85.5– 96(–96) × (42–)43–54–65(–66) µm (N = 20). Ascospores (N = 60) (17.5–)17.8–21.3–24.8(–25.0) × (17.5–)17.6– 21.0–24.4(–24.5) µm, Q = (1.00–)0.97–1.02–1.06(–1.12), globose to subglobose, pale yellow-brown, ornamented with straight or slightly curved stick-like sparse spines, 2–3 µm tall, with truncate or rounded tips ( Fig. 2e–g ).

Habitat, phenology, and distribution: Growing under Abies delavayi Franch. , Rhododendron simsii Planch. and Pinus yunnanensis in mixed evergreen hill forest, in late autumn. So far found in Diqing and Yongren counties, Yunnan, China.

Other material examined: CHINA, Yunnan Province, Chuxiong Autonomous Prefecture , Yongren County, 26.0810°N 101.6632°E, elevation 1,834 m, under Pinus yunnanensis in mixed evergreen hill forest, with soil types mainly red and brown soils, 01 Nov. 2019, collected by H. K . Xiong. ( YAAS TJ16-1 and YAAS TJ16-2 ) .

Remarks: Choiromyces cerebriformis is characterized by hypogeous, glabrous, pale yellow or white, irregularly knobby, much lobed ascomata, and globose spores ornamented with conspicuous, straight or slightly curved spines with truncate or rounded tips when observed with SEM. This species resembles white Tuber truffles with white ascomata and sinuous veins in gleba. However, it is different from those Tuber species and from other Choiromyces species by its globose spores ornamented with conspicuous spines and small pits. C. cerebriformis can be further distinguished from C. meandriformis , which has paler gleba, and spores with much taller spines ( Csorbainé et al. 2009; Moreno et al. 2012). C. echinulatus Trappe & Marasas ( Ferdman et al. 2005) , differs from C. cerebriformis by spores with straight, obtuse spines ˂ 2 µm high (spines are 2–3 µm high in C. cerebriformis ). Moreover, C. echinulatus has tissues with greatly inflated cells, which is characteristic of all desert truffles. C. cerebriformis differs from C. alveolatus ( Liu et al. 1990) in having larger asci (75–96 × 42–66) µm, mostly with 8 spores, compared to 40–85 × 30–55 µm asci, with (2–) 4–6 spores in the latter species. C. magnusii ( Moreno et al. 2012) spores ornamentation is verrucose-reticulated with a minutely-meshed reticulum, which is clearly different from C. cerebriformis . C. helanshanensis ( Chen et al. 2016) differs from C. cerebriformis by its coarsely knobby ascomata 2–8 cm diam (ascomata up to 10 cm and with larger, deeper lobes in C. cerebriformis ) and ascosporal ornamentation as conspicuous dense spines (as short stick-like sparse spines in C. cerebriformis ).

Figures

FIGURE 2. Choiromyces cerebriformis. a. The habitat of Choiromyces cerebriformis. b. Fresh ascomata. c. A sectioned ascoma showing the gleba. d. Peridium with two differentiated pseudoparenchymatous layers. e–f. Ascospores. g. SEM photos of ascospores. Scale bars c = 5 cm; d = 50 μm; e–f = 20 μm; g = 2 μm.