Rossbeevera subalbida (Boletaceae, Boletales), a new, rare truffle-like species from Japan
国内に稀産する新種トリュフ型菌、 ウノハナツチダマタケ Rossbeevera subalbida (イグチ目イグチ科)

Article info

Takamichi Orihara (2026) Truffology 9(1): 17–23
Submitted: 23 February 2026
Accepted: 25 March 2026
Published: 31 March 2026

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Abstract

The genus Rossbeevera comprises truffle-like species characterized by rubbery basidiomata with bluish discoloration and fusoid to citriform basidiospores with 3–5 prominent longitudinal ridges. In this study, Rossbeevera subalbida, is described as a new species from Japan based on morphological characteristics and phylogenetic analyses of the internal transcribed spacer region and the large subunit (28S) of the nuclear ribosomal RNA gene. To date, this species has been collected only sporadically in association with evergreen Quercus spp. and Castanopsis sieboldii across Honshu, Kyushu and Hachijo Island. Morphologically, this species is characterized by its persistent, white to whitish peridium and basidiomata with very weak bluish discoloration. The hylogenetic analyses revealed that R. subalbida is sister to R. griseovelutina, a more common, widely distributed species throughout Japan. Key diagnostic characters separating R. subalbida from other morphologically similar Rossbeevera species are provided, and the rarity of this species and its potential distribution are also discussed.

要旨

トリュフ型地下生菌からなるツチダマタケ属Rossbeevera は、青変性のある子実体と紡錘形～レモン型で3–5つの大きな畝をもつ担子胞子を特徴とする一群である。本研究では、本州、九州および八丈島のカシ類及びスダジイ樹下の計3地点から採集された本属菌標本の形態学的検討および分子系統解析結果に基づき、新種Rossbeevera subalbida を記載した。本種は子実体の青変性が弱く、白色～帯白色で残存性の外皮を有する点により形態的に特徴づけられる。核rDNAのITS領域および大サブユニット（LSU）を用いた分子系統解析の結果、本種は日本国内に広く分布するR. griseovelutina と系統的に姉妹関係にあることが示された。また、本稿では種の記載、類似種との識別点を詳述したほか、本種の希少性および潜在的分布についても考察を加えた。なお、本種の和名は、子実体の特徴的な色合いを日本の伝統色の一つである卯の花色に見立て、ウノハナツチダマタケ（新称）)とする。

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