クレナイセイタカイグチ

Aureoboletus cf. betula (Schwein.) M. Kuo & B. Ortiz, Mycologia 112(1): 205 (2020) 

Basionym: Boletus betula Schwein., Schr. naturf. Ges. Leipzig 1: 90 (1822)

≡  Boletellus betula (Schwein.) E.-J. Gilbert, Bolets: 108 (1931).

≡ Austroboletus betula (Schwein.) E. Horak, Sydowia 33: 72 (1980)

≡ Heimiella betula (Schwein.) Watling, in Watling & Hollands, Notes R. bot. Gdn Edinb. 46(3):

420 (1990)

≡ Heimioporus betula (Schwein.) E. Horak, Sydowia 56(2): 239 (2004)

1997年に山梨県北杜市のアカマツ-ミズナラ林内で発見され、日本新産種として発表されました (Takahashi and

 Degawa 2011)。国内では分布域が限られており、山梨県以外では発生が極めて稀な超珍菌です。

Boletus betula Schwein.の基準標本産地は北米北東部で、日本産クレナイセイタカイグチは隔離分布しているため、形態以外の性質において遺伝的に分化した隠蔽種の可能性があります。

種小名の「betula」はカバノキ属を意味し、Smith 博士(Weber and Smith 1985)によれば、 柄の表面の粗大で縦長の網目状隆起がカバノキの樹皮を連想させることに由来すると言われています。

北米産B. betulaは、最近ヌメリコウジタケ属に転属しましたが、胞子の構造や子実体の外観がヌメリコウジタケの仲間と大きく異なり、強い違和感を覚えます。

日本から既にヒゴノセイタカイグチの和名で熊本県産の報告例(熊本きのこの会 1992)がありますが、一個のみの乾燥標本と写真に基づく同定で、詳細な記載報告がなされておらず、別種の可能性も考えられるので、上記の和名を提唱しました。

 文献

Kumamoto Kinoko kai (1992) "Kumamoto no kinoko (Mushrooms of Kumamoto pref.)" Kumamoto Nichinichi Shinbunsha, Kumamoto 

Takahashi, H.; Degawa, Y. 2011. Two new species of Agaricales and a new Japanese record for Boletellus betula from Japan. Mycoscience. 52(5):312-318 

Weber NS, Smith AH (1985) A Field Guide to Southern Mushrooms. University of Michigan Press.

Photo by Mr. Haruo Sakamoto

　 肉眼的特徴: 傘は径 40-95 mm, 最初饅頭形のち平たい饅頭形になり, 縁部は全縁で突出

しない; 表面は平滑, 湿時粘性, 暗赤色～橙赤色, 時に明るい黄色または黄褐色～赤褐色を帯

び, しばしば周縁部は黄色を呈する. 肉は緑黄色～橙黄色, 傷ついたり空気に触れても変色せ

ず, 特別な味や匂いはない. 柄は 80-210×8-20 mm, ほぼ上下同大または頂部に向かってや

や細くなり, 中心生, 中実; 表面は最初上部黄色で下方に向かって暗赤色を帯び, 老成すると

全体が暗赤色を呈し, 赤色～黄色の粗大で縦長の網目状隆起に全体が被われる; 根元の菌

糸体は白色. 管孔は柄の周囲で急激に深く嵌入し, 長さ8-22mm, 黄色～緑黄色; 孔口は角形,

1mm以下, 管孔と同色, 管孔及び孔口は傷を受けても変色しない. 胞子紋は暗オリ－ブ～オリ

－ブ褐色.

　 顕微鏡的特徴: 担子胞子は 18-22×8-11μｍ, 狭楕円形, 頂部は切形でややギザギザ状

になり, 表面に点状の小孔を持ち粗面を呈し, 淡オリーブ黄色～オリ－ブ褐色, アミロイド, 厚

壁 (0.5-1μm). 担子器は 22-30×7-10μm, こん棒形, 4 胞子性. 縁シスチジアは 30-60×5-

10μｍ, 群生, 頂部が細長く伸びた紡錘形～片脹れ状, 無色～淡黄色, 薄壁. 側シスチジアは

40-75×5-17μｍ, 散生, 頂部が細長く伸びた片脹れ状～紡錘形, 無色～淡黄色, 薄壁.  子実

層托実質は平列し, 菌糸は幅 5-15μm, 無色～淡黄色, 非アミロイド～弱アミロイド, 薄壁. 傘

の表皮は緩く錯綜した毛状被からなり, 菌糸は幅 5-10μｍ, ゼラチン化し, 円柱形, ワイン赤色

の色素が細胞内に存在し, アミロイド, 薄壁, 稀に黄褐色の内容物を持つ菌糸が混在する. 傘

実質の菌糸は不規則に錯綜し, 幅10-22μm, 無色, 薄壁. 柄の表皮はこん棒形の偽担子器型

細胞(25-40×12.5-20μm)が子実層状被を形成し, 淡黄色～黄褐色またはワイン赤色の色素

が細胞内に存在する. 柄の実質は縦に沿って配列した円柱形の菌糸 (幅 5-12.5μm)からな

り, 淡黄色またはワイン赤色, 薄壁.  全ての菌糸はクランプを欠く.

  供試標本: KPM-NC0007423, 山梨県北杜市, 1997年8月21日, 標高887m, アカマツ-ミズ

ナラ林内地上に散生, 採集: 坂本晴雄, 上原貞美, 横山元, 同定: 高橋春樹; KPM-NC0017296, 

same place, Oct. 5, 2007, coll. Uehara, S.

  コメント: 肉眼的にはセイタカイグチを赤くしたような印象を受けるが, 担子胞子の表面はセ

イタカイグチのような縞模様と異なる点状の小孔を形成し, 傘の表皮組織の菌糸がアミロイドに

染まる性質を持つ.

    分布は北米(フロリダを除く), 中国安徽省 (Teng 1996), メキシコ(Singer et al. 1992), 日本 

(山梨県北杜市, ?熊本県熊本市).

  生態写真1-5は埼玉きのこ研究会の坂本晴雄氏によって撮影された.

  図および記載データはすべて山梨県北杜市で採集された標本に基づく.

Aureoboletus cf. betula (Schwein.) M. Kuo & B. Ortiz, Mycologia 112(1): 205 (2020) 

Basionym: Boletus betula Schwein., Schr. naturf. Ges. Leipzig 1: 90 (1822)

≡  Boletellus betula (Schwein.) E.-J. Gilbert, Bolets: 108 (1931).

≡ Austroboletus betula (Schwein.) E. Horak, Sydowia 33: 72 (1980)

≡ Heimiella betula (Schwein.) Watling, in Watling & Hollands, Notes R. bot. Gdn Edinb. 46(3):

420 (1990)

≡ Heimioporus betula (Schwein.) E. Horak, Sydowia 56(2): 239 (2004)

Macromorphological features:

　 Pileus (Figs. 10, 11) 40-95 mm in diam, at first hemispherical, expanding to broadly 

convex, with straight margin, not appendiculate; surface glabrous, smooth, viscid when wet, 

at first greyish red (8C4-5) or brownish red (8C4-5), then orange red (8A7-8 to 8B7-8), 

with a light yellow (3A5) to yellow (3A6) margin, at times yellow (3A6) overall. Flesh up to 10 

mm thick, pale yellow (3A3) to light yellow (3A4-5), orange red (8A7-8 to 8B7-8) right 

beneath the pileus surface, whitish at the base of stipe, unchanging or sometimes changing 

to orange red (8A7-8 to 8B7-8) where bruised; odor and taste indistinct. Stipe 80-210 × 8

-20 mm, subequal or somewhat tapering toward the apex, central, terete, solid; surface dry, 

coarsely lacunose-reticulated overall, with longitudinally raised, yellow (3A6) reticulum, 

concolorous with the pileus below, yellow (3A6) above, sometimes entirely becoming orange 

red (8A7-8 to 8B7-8) in age; base covered with whitish mycelial tomentum. Tubes 8-22 mm 

deep, depressed around the stipe, yellow (3A6-7) or greyish yellow (3B6-7), unchanging 

when bruised; pores up to 1 mm, subcircular, concolorous with the tubes.

Micromorphological features:

　 Basidiospores (Fig. 16-17) 18-22 × 8-11 μm (Q = length/breadth: 2-2.25), inequilateral 

with a shallow suprahilar depression in profile, oblong ellipsoid to subfusoid in face view, with 

a truncate and seemingly eroded apex, ornamented with crowded pits over the entire 

surface, greyish-yellow (4C6-7) to brownish-yellow (5C6-7), distinctly amyloid, thick-walled 

(0.5-1 μm). Basidia (Fig. 14) 22-30 × 7-10 μm, clavate, four-spored. Basidioles (Fig. 14) 

clavate. Cheilocystidia (Fig. 13) gregarious, 30-60 × 5-10 μm, fusoid-ventricose to 

ventricose-rostrate with an obtuse apex, smooth, hyaline to pale yellow, inamyloid, thin-

walled. Pleurocystidia (Fig. 15) scattered, 40-75 × 5-12(-17) μm, similar to cheilocystidia.  

Hymenophoral trama with parallel, cylindrical hyphae 5-15 μm wide, smooth, hyaline or 

yellowish white (3A2) to pale yellow (3A3), inamyloid or weakly amyloid, thin-walled.  

Pileipellis (Fig. 12) of an ixotrichoderm consisting of loosely interwoven hyphae 5-10 um 

wide, cylindrical, smooth, gelatinized, colorless or with intracellular brownish red (10C7) to 

dark red (10C8) pigment, distinctly amyloid, thin-walled. Pileitrama of cylindrical, loosely 

interwoven hyphae 10-22 μm wide, smooth, colorless or yellowish white (3A2), inamyloid, 

thin-walled. Stipitipellis hymeniform, consisting of caulocystidia which distribute the entire 

stipe surface; caulocystidia 25-40 × 12.5-20 μm, broadly clavate, smooth, with 

intracellular yellowish white (3A2) to pale yellow (3A3) or brownish red (10C7) to dark red 

(10C8) pigment, inamyloid, thin-walled. Stipe trama composed of longitudinally running, 

cylindrical cells 5-12.5 μm wide, unbranched, smooth, colorless or yellowish white (3A2) to 

pale yellow (3A3), inamyloid, thin-walled. Clamp connections absent.

    Known distribution: USA, Mexico, China, Japan. 

    Habitat: Solitary or scattered, on ground in mixed forests dominated by Quercus 

crispula Blume and Pinus densiflora Siebold & Zucc. 887 m alt.

   Specimens examined: KPM-NC0007423, Hokuto-shi, Yamanashi pref., on ground in Q.

crispula and P.densiflora forests, 887 m alt., Aug. 21, 1997, coll. Sakamoto, H., Uehara, S., 

Yokoyama, H.; KPM-NC0017296, same place, Oct. 5, 2007, coll. Uehara, S.

   Comments: Boletellus betula (Schwein.) E.-J. Gilbert was originally described from USA, 

and is also known from Mexico (Singer et al. 1992) and China (Teng 1996). Although the 

fruiting body of B. betula has outstanding macroscopic characteristics, it has not yet been 

fully described with regard to micromorphological features. The earliest report of this 

species in Japan was given by Kumamoto Kinoko Kai (1992) from Kumamoto pref. on the 

basis of only one specimen. Unfortunately the identification is not reliable, as no microscopic 

information was provided and the specimen is not available.

  Except for the distinctly amyloid pileipellis elements, our material fully conforms to the 

descriptions given by the North American authors (Thiers 1963; Snell and Dick 1970; Smith 

and Thiers 1971; Bessette et al. 1997, 2000). At the collection locality in Japan (Hokuto-shi, 

Yamanashi pref.), the species commonly occurs in the mixed forest of Q. crispula and P.

densiflora in summer to early fall. 

  Singer (1945a) created the new section Allospori Singer, in the genus Boletellus, to 

include the species with pit-like perforated basidiospores. Recently Horak (2004) proposed 

the new genus name Heimioporus for Heimiella Boedijn (syn. Post.), and incorporated the 

Boletellus taxa with smooth and pit-like perforated basidiospores into Heimioporus. 

Heimioporus, however, seems to be a highly artificial genus because of the obvious 

overestimation of a single specific character, viz. the difference only in the basidiospore 

morphology. Furthermore, there is no closely related taxon in the other allied genera with a 

yellowish hymenophore such as the genus Boletus. Because of its striking 

macromorphological resemblance to Boletellus russellii except for the spore morphology, 

here we prefer to accommodate this species in the genus Boletellus.

Literature cited

Bessette AE, Bessette AR, Fischer DW (1997) Mushrooms of northeastern North American. Syracuse University Press, New York　

Bessette AE, Roody WC, Bessette AR. (2000) North American boletes. A color guide to the fleshy pored mushrooms. Syracuse University Press, New York　

Horak E (2004) "Heimioporus E. Horak gen. nov. - replacing Heimiella Boedijn (1951, syn. post., Boletales, Basidiomycota)". Sydowia 56(2):237-240

Kornerup A, Wanscher JH (1983) Methuen handbook of colour. Eyre Methuen, London

Kumamoto Kinoko kai (1992) "Kumamoto no kinoko (Mushrooms of Kumamoto pref.)"  Kumamoto Nichinichi Shinbunsha, Kumamoto

Pegler DN, Young TWK (1981) A natural arrangement of the Boletales, with reference to spore morphology. Trans. Br. mycol. Soc. 76(1):103-146

Singer R (1945) The Boletineae of Florida with notes on extralimital species I. The Strobilomycetaceae. Farlowia 2(1):97-141 

Singer R, Garcia J, Gomez Ld (1992) The Boletineae of Mexico and Central America . Beih. Nova Hedwigia 105:1-62

Smith AH and Thiers HD (1971) The boletes of Michigan. The University of Michigan Press, Ann Arbor.　

Snell WH, Dick EA (1970) The boleti of northeastern North America. J.Cramer, Vaduz 

Takahashi H, Degawa Y (2011) Two new species of Agaricales and a new Japanese record for Boletellus betula from Japan. Mycoscience Volume 52, Number 5, 312-318. 

Teng SC (1996) Fungi of China (edited by Richard P. Korf). Mycotaxon, Ithaca, New York

Thiers HD (1963) The bolete flora of the Gulf coastal plain. I. The Strobilomycetaceae. J. Elisha Mitchell Sci. Soc. 79:32-41

* Color notations in parentheses are taken from Kornerup and Wanscher (1978).