Melanogaster truncatisporus T. J. Yuan, Shu H. Li, & Raspé, 2024

Yuan, Tian-Jun, Luo, Hong-Mei, Su, Kai-Mei, Li, Shu-Hong & Raspé, Olivier, 2024, Three new Melanogaster species (Boletales, Paxillaceae) from southwestern China based on morphological and molecular evidence, MycoKeys 107, pp. 141-160 : 141-160

Melanogaster truncatisporus T. J. Yuan, Shu H. Li, & Raspé sp. nov.

Fig. 3 i – l

Diagnosis.

Melanogaster truncatisporus is diagnosed by the combination of medium-sized basidiomata with orange-yellow peridium that becomes reddish brown to dark brown in age, and truncate basidiospores.

Etymology.

The epithet truncatisporus refers to the truncate basidiospores.

Holotype.

China. Yunnan Province: Nujiang Autonomous Prefecture, Lanping County, Zhongpai township, Xinchangping village , 26 ° 54 ' 15 " N, 99 ° 10 ' 32 " E, elevation 1990 m, in mainly brown soils under Castanea mollissima and Pinus yunnanensis Franch. , 26 Oct. 2020, collected by T. J. Yuan ( KUN-HKAS 129199 , holotype; YAAS -TJ87 , isotype) .

Description.

Basidiomata 1.5–3.0 × 0.4–2.3 cm, hypogeous or semi-hypogeous, subglobose to oval, occasionally irregular-elongated, yellowish when young, reddish brown to dark brown at maturity, smooth or slightly velvety surface, lobed or indented at the base, attached mycelial strands, occasionally extending to the surface, dark brown, rhizomorphs not distinct (Fig. 3 i ). Peridium two-layered, outer layer 50–100 μm thick, composed of interwoven hyphae, orange-yellow, with clamp connections, and fusoid to cylindrical terminal cells, 4–5 μm broad; inner layer 150–350 μm thick, composed of interwoven hyphae, 3–5 μm broad, pale yellow, intermixed with massive inflated cells, ellipsoidal or irregular, 3–20 μm broad. Gleba solid, pale brown when young, blackish brown to black at maturity, separated by white or pale yellow trama when young, which becomes deep brown at maturity, hard when dried; trama plates of hyaline or yellowish gelatinized hyphae (Fig. 3 j ); locules 2–4 mm in diameter, polygonal to irregular (Fig. 3 k ). Basidia poorly recovered, hyaline, 4 – spored, occurring randomly in the locules (Fig. 3 k ). Basidiospores subglobose to globose or irregularly elongate-pyriform, 3.5–9.5 × 3.0–7.0 μm (L m × W m = 7.0 ± 2.5 × 4.5 ± 2.0, Q = 1.0–2.5, Q m = 1.5 ± 1.0, n = 65), hyaline when immature, becoming dark brown at maturity, smooth, with truncate-cupped base and short hilar appendage, 1–2 μm in diam in optical microscopy (Fig. 3 l ).

Habitat, phenology, and distribution.

hypogeous to semi-hypogeous under Castanea mollissima and Pinus yunnanensis , in mixed forest, in late autumn. So far found in Lanping and Gongshan counties, Yunnan Province, China.

Other material examined.

China. Yunnan Province: Nujiang autonomous Prefecture, Lanping County , 26 ° 54 ' 17 " N, 99 ° 10 ' 31 " E, elevation 2,030 m, in mainly brown soils under Castanea mollissima and Pinus yunnanensis , 26 Oct. 2020, collected by T. J. Yuan ( YAAS TJ 83 and YAAS TJ 109 ) ; China. Yunnan Province: Nujiang Autonomous Prefecture, Gongshan County , 28 ° 1 ' 19 " N, 98 ° 37 ' 2 " E, elevation 1,800 m, in mainly brown soils under Castanea mollissima and Pinus yunnanensis , 25 Sep. 2020, collected by Li, S. H. ( YAAS L 5346 ) .

Notes.

Four Melanogaster species, namely M. minysporus ( Cázares et al. 2008) , M. broomeanus Berk ( Türkoğlu and Castellano 2013, Uzun et al. 2014), M. obovatisporus ( Liu et al. 1989) , and M. variegatus ( Krisztián 2008) , are similar in morphology and related to M. truncatisporus by phylogeny. M. truncatisporus can be easily differentiated by its peridium thickness ( M. truncatisporus , 200–450 μm vs M. minysporus , 160–240 μm) and the size of basidiospores ( M. truncatisporus , 3.5–9.5 × 3.0–7.0 μm vs M. minysporus , 5–6.5 × 3–5 μm). M. truncatisporus has a two-layered peridium and M. broomeanus has a single-layered peridium. The difference in basidiospore size is evident, with 3.5–9.5 × 3.0–7.0 μm for M. truncatisporus and 7–9 × 4 μm for M. broomeanus . Also, M. truncatisporus basidia typically contain 4 spores, whereas those of M. obovatisporus consistently contain 8 spores. Basidiospore size (especially minimum size) is also a diagnostic character to separate M. truncatisporus from M. variegatus (3.5–9.5 × 3.0–7.0 μm for the former, and 7.5–10 × 5.5–8 μm for the latter). Phylogenetically, the specimens of M. truncatisporus clustered in an independent clade with strong support (BS = 100 %, PP = 1.0; Fig. 2 ), supporting it as a new species. Additionally, M. truncatisporus (holotype ITS sequence ON 427479 ) shared less than 93.2 % similarity with ITS sequences of other Melanogaster species.

Figures

Figure 2. The ITS phylogram of Melanogaster obtained with RAxML (including ITS 1, ITS 2, and 5.8 S). The six Alpova cessions were chosen as the outgroup. Nodes were annotated with ML BS > 70 %, Bayesian PP > 0.90, or “ - ” in case of non-significant support value. New species are in bold font. The sections are as defined by Moreau et al. 2011 on the basis of basidiospore length.

Figure 3. Photographs of Melanogaster species. Melanogaster cyaneus (YAAS - TJ 75-1, holotype) a basidiomata b LM of Peridium c LM of basidiospores d SEM of basidiospore. Melanogaster diqingensis (YAAS - WXH _ 9068, holotype) e basidiomata f LM of Peridium g LM of basidiospores h SEM of basidiospore. Melanogaster truncatisporus (YAAS - TJ 87, holotype) i basidiomata j LM of peridium k LM of basidiospores l SEM of ascospore. Scale bars: 2 cm (a, e, i); 20 μm (b, f, g); 10 μm (c, g, k); 1 μm (d, h, l).