Tuber marroninum T. J. Yuan, S. H. Li & X. H. Wang, 2025

Yuan, Tian-Jun, Luo, Hong-Mei, Su, Kai-Mei, Li, Shu-Hong & Li, E-Xian, 2025, Two novel Tuber species (Tuberaceae, Pezizales) from southwestern China based on morphological and molecular evidence, MycoKeys 119, pp. 295-314 : 295-314

Tuber marroninum T. J. Yuan, S. H. Li & X. H. Wang sp. nov.

Fig. 3 a – g

Typification.

China • Yunnan Province: Xiangyun County (25°20'768"N, 100°43'34"E), in soil under mixed forest, with Pinus yunnanensis dominant, 20 Sep 2020, S. H. Li L 3694 (holotype YAAS L 3694 , paratype YAAS L 3695 ) .

Gene sequences ex holotype.

ON 454668 (ITS); ON 428904 (LSU); OQ 305202 (RPB 2); OQ 305199 (TEF 1); ex paratype: OQ 297680 (ITS).

Etymology.

“ Marroninum ” refers to the maroon color of the ascoma.

Diagnosis.

Tuber marroninum differs from other species by its whitish and glabrous ascomata and maroon color of the ascoma, globose and subglobose or broad ellipsoid ascospores, with greyish-white alveolate-reticulate ornamentation.

Description.

Ascomata (Fig. 3 a, b ) 3–5 cm diam, subglobose, hypogeous, whitish (3 A 1-2) becoming brown (8 E 6-8) when bruised, surface smooth, with white furrows; odor mild, taste not recorded. Peridium (Fig. 3 c, d ) two-layered, 150–200 µm thick, outer layer 40–60 µm thick, pseudoparenchymatous, composed of subglobose or irregularly shaped cells of 7.5–16.8 (24.5) µm broad with thickened walls, inner layer composed of thin-walled hyaline interwoven hyphae, 2.5–4 (5.5) µm diam, large cells of 20 × 10 µm diam. Sometimes, intermixed. Gleba (Fig. 3 b ) solid, firm, brown to dark brown (10 F 6-8) at maturity, marbled with whitish (1 A 1-1 B 1) narrow veins. Asci (Fig. 3 e, g ) subglobose or irregular, 1–4 spored, with a short stalk, 50–75 (100) × 40–55 (80) μm (n = 50). Ascospores (Fig. 3 e, g ) subglobose to globose, pale yellow (5 A 2-3, 5 B 3) when young, becoming brown (5 C 6-8, 5 D 6-7) at maturity, excluding their spiny-reticulate ornamentation, 41.5–52 × 41–50 μm, Q = 1.00–1.14 (n = 55), in one-spored asci, 33–41 × 32–40 μm (n = 50), Q = 1.00–1.15, in two-spored asci, 21–37 × 20–35.5 μm, Q = 1.01–1.12 (n = 60), in three-spored asci, 20–35.5 × 18.5–30.5 μm, Q = 1.02–1.15 (n = 60), in four-spored asci, Q = 1.14 ± 0.07, with a greyish white (2 B 1-2; 1 C 1-2) reticulatum and alveolate-reticulate ornamentation, meshes 5–8 across the ascospore width, 1.5–3 μm tall.

Distribution and habitat.

China: Yunnan province, Xiangyun county, hypogeous, in the soil in mixed woods dominated by Pinus yunnanensis .

Notes.

Tuber marroninum is phylogenetically closely related to T. caoi ( Fan et al. 2016) . In morphology, T. caoi has gray and pubescent ascomata, but T. marroninum has whitish and glabrous ascomata. Both trees of ML and BI (Figs 1 , 2 ) also have strong bootstrap supporting the new species.

Figures

Figure 1. Phylogeny generated from maximum likelihood and Bayesian inference analysis of the ITS-LUS-TEF 1 - RPB 2 rDNA sequences from Tuber marroninum and T. conditum - related species. Choiromyces helanshanensis and C. meandriformis served as outgroups. ML bootstrap values (> 75 %) and Posterior Probabilities (PPs) values (> 0.90) are shown above or beneath the branches at nodes. Novel sequences are printed in bold.

Figure 2. Phylogeny generated from maximum likelihood and Bayesian inference analysis of the ITS 1-5.8 S-ITS 2 sequences from Tuber marroninum and T. conditum related species. Choiromyces helanshanensis and C. meandriformis served as outgroups. ML bootstrap values (> 75 %) and Posterior Probabilities (PPs) values (> 0.90) are shown above or beneath the branches at nodes. Novel sequences are printed in bold.

Figure 3. Photographs of Tuber marroninum (YAAS L 3694, holotype): a fresh ascomata showing cut section b the gleba c, d vertical section of peridium d the gleba and asci e, f ascospores g scanning electron micrograph of ascospore.