シラガニセホウライタケ 

Moniliophthora canescens (Har. Takah.) Kerekes & Desjardin, Fung Diver 37: 137 (2009).

≡  Crinipellis canescens Har. Takah., Mycoscience 41 (2): 171 (2000).

八重山諸島で普通に見られるニセホウライタケの仲間で、マレーシアとオーストラリアにおいて本種と外観が酷似した類似菌が知られています。

和名の「シラガ」は、幼菌が白髪のような毛に被われることに由来します。

4月～11月、シシアクチなどの常緑低木の枯れ枝上に発生します。今のところ確実な分布は八重山諸島のみですが、沖縄本島地方並びに台湾にも分布している可能性があります。

主な形態的特徴

ア) 傘は放射状の溝線を表し, 白色の微毛に被われ, 成熟時帯褐黄色を呈する.

イ) 柄は白色または帯褐色, 微毛～剛毛に被われ, 根元は基質を被う圧着した白色の菌糸マットに接続する.

ウ) 縁シスチジアは亜こん棒形～不規則な形状を成し, 1-数個の短指状付属糸を持つ.

エ) 傘および柄の表面は偽アミロイドに染まる毛状末端細胞に被われる.

 肉眼的特徴: 傘は径 6–15 mm, 最初縁部は内側に巻き, 半球形, のち饅頭形～平らに開き, 時に中丘を具えるかまたは中央部が凹み, 放射状に溝線を表す; 表面は乾性, 全体に白い微毛に被われ, 微毛の下は最初赤褐色, のち中央部は褐色で周縁部に向かって黄褐色を帯び, 湿時橙褐色を呈する. 肉は非常に薄く (0.3 mm以下), 傘の表面と同色, 弾力性があり, 質は強靱, 特別な味や匂いはない.　柄は 10–15 × 0.5–1 mm, ほぼ上下同大または基部において僅かに拡大し, 中心生, やせ型, 中空, 最初は全体に白色, のち根本にかけて褐色を帯び, 上部は白色粉状, 下部は微毛を帯び, 根元は基質を被う発達した白色菌糸体に接続する.　ヒダは上生～不完全な襟帯を形成し, 疎 (柄に到達するヒダは14–18), 小ヒダは0–1, 幅1 mm以下, 僅かに連絡脈を形成し, 傘と同色. 胞子紋は白色.

  顕微鏡的特徴: 担子胞子は 9.2–10.4 × 3.7–4.3 μm (n = 34, Q = 2.41–2.48), 楕円形, 平坦, 無色, 非アミロイド, 薄壁. 担子器は 26.4–37.3 × 6.4–8.8 μm, こん棒形, ４胞子性; 偽担子器はこん棒形. 縁シスチジアは 16–21.6 × 5–8.5 μm, 不稔帯を形成し, 亜こん棒形～不規則な形状をなし, 頂部に 1-数本の短指状突起 (幅2.4–4.2 μm) を持ち, 無色または淡黄色, 非アミロイド, 薄壁. 側シスチジアはない. 子実層托実質は平列型, 菌糸は傘実質と同じ. 傘表皮組織は毛状末端細胞に接続する亜円柱形の菌糸が平行菌糸被を成す; 菌糸細胞は 30–60 × 6–12 μm, しばしば膨大し, 壁は厚さ1 μm以下, 橙褐色の色素が凝着し, 偽アミロイド; 毛状末端細胞は 230–1200 × 4–7 μm, 匍匐性または直立し, 円柱形, 鈍頭, 一般に頂部に向かって次第に細くなり, 時に屈曲し, 平滑, 強偽アミロイド (紫褐色) に染まり, 壁は無色または淡い蜜色で厚さ1.6–3.2 μm, 二次隔壁を欠く. 傘実質を構成する菌糸は幅 6–16 μm, 並列し, 円柱形～亜紡錘形, しばしば膨大し, 平滑, 淡い蜜色の細胞内色素を持ち, 偽アミロイド, 薄壁. 柄表皮組織は平行菌糸被を成し, 束状に配列した毛状末端細胞に接続する; 毛状末端細胞は傘と同様. 柄実質の菌糸は幅 5.3–8 μm, 縦に沿って配列し, 円柱形, 平滑, 淡い蜜色～帯褐橙色の細胞内色素を有し, 偽アミロイド, 薄壁. 全ての組織においてクランプが存在する.

  生態および発生時期: シシアクチなどの常緑低木の枯れ枝上に孤生または散生, 4月～11月, 普通種.

分布: 沖縄 (八重山諸島: 石垣島, 西表島), マレーシア (Kerekes and Desjardin 2009).

供試標本: KPM-NC0005014 (正基準標本), 常緑低木の枯れ枝上, 沖縄県西表島浦内川流域, 1999年6月2日, 高橋春樹採集; CBM-FB-24120, 同上, 1996年10月1日, 高橋春樹採集; CBM-FB-24121, 同上, 1997年5月15日, 高橋春樹採集; CBM-FB-24122, 同上, 1998年6月6日, 高橋春樹採集; TNS-F-48181, 常緑低木の枯れ枝上, 石垣市オモト山, 2012年6月9日; KPM-NC0023876, シシアクチの落枝上, 沖縄県石垣市バンナ岳, 2013年6月2日, 高橋春樹採集.

コメント: 明るい色素を欠き, 相対的に長い (7 mm以下) 中心性の柄, 幅9 μm以下の楕円形の担子胞子, そして側シスチジアを欠く性質は本種がニセホウライタケ属Crinipellis, ニセホウライタケ節section Crinipellis, ニセホウライタケ亜節subsection Crinipellis (Singer 1942, 1986) に属することを示唆している.

亜節内においてシラガニセホウライタケは径10 mm以下の小形の傘と複数の付属糸を持つ縁シスチジアの特徴において以下の新熱帯産分類群に近縁と思われる: Crinipellis pseudostipitaria Singer (Pegler, 1983; Singer, 1942); Crinipellis septotricha Singer (Pegler, 1983; Singer, 1942); Crinipellis stupparia (Berk. & M.A.Curtis) Pat. (Pegler, 1983). しかしながらこれら新熱帯産分類群は傘が乳頭状中丘を形成し, 根元に発達した菌糸体を欠くと言われている. さらにC. pseudostipitariaは草本の残骸から発生し, またC. septotricha および C. stuppariaは毛状末端細胞に梯子状二次隔壁を有する. スリランカ産Crinipellis omotricha (Berk.) D.A. Reid (Pegler, 1986) も本種に類似するが, 縁シスチジアは付属糸を欠き, 草本を基質とする点でシラガニセホウライタケと異なる. マレーシア産Crinipellis hepatica Corner (Corner, 1996) はシラガニセホウライタケに最も近縁と考えられるが, 傘は赤褐色を帯びること, 柄の根元に発達した菌糸体を持たないこと, 亜紡錘形の偽担子器を形成すること, そして付属糸を欠く縁シスチジアを有する性質において本種と区別できる.

 Kerekes and Desjardin (Kerekes and Desjardin 2009) はマレーシア産標本を用いたITS領域の分子解析データに基づき Moniliophthora属 (Evans et al. 1978; Aime and Phillips-Mora 2005) に本種を転属させた. 

Moniliophthora属は, ホウライタケ科に属し、基準種に指定されている南米産 Monilia roreri は、英語で魔女の箒 (witches’ broom) と呼ばれるカカオのてんぐ巣病の起因菌（the causal agent of witches’ broom of cacao）で, 最初子嚢菌の不完全世代として記載された. 既知種については、今のところ16分類群（Index Fungorum）知られており, Moniliophthoraは一般に明るい色素 (赤, 紫赤, 深紅, 紫灰, 青紫) を有し、アルカリ溶液により緑変しない性質があり, 植物寄生性であるのに対し, ニセホウライタケ属は腐生性であるという生態的相違はあるが, 両属の形態学的区別は難しく, ニセホウライタケ属 (Crinipellis) に置かれている分類群についても, 特にSinger (1986)の分類概念による Sect. Iopodinaeは将来的に Moniliophthora属と統合される可能性がある. もし両属が系統的に同一分岐群であることが証明された場合は, 命名規約上ニセホウライタケ属が有効名になるが, 現時点では Moniliophthora属の和名をシラガニセホウライタケ属としておく. 

Moniliophthora canescens (Har. Takah.) Kerekes & Desjardin, Fung Diver 37: 137 (2009).

≡  Crinipellis canescens Har. Takah., Mycoscience 41 (2): 171 (2000).

  Etymology: The specific epithet refers to the hoary fibrils enveloping the pileus and stipe.

  Macromorphological characteristics (Figs. 47–51): Pileus 6–15 mm in diameter, at first hemispherical with incurved margin, then convex to plane, sometimes with an obtuse umbo or depressed center, radially sulcate-striate up to the disk; surface dry, covered overall with white, fine, pubescent hairs, at first reddish brown (8F7–8, 9F7–8) under hoary fibrils, then brown (7E7–8, 8E7–8) at center, brownish yellow (5C7–5C8) to yellowish brown (5D7–5D8) toward the ciliate-villose margin, orange (6B8) to brownish orange (6C8) when wet. Flesh very thin (up to 0.3 mm), concolorous with the surface, pliant, tough, odor and taste none. Stipe 10–15 × 0.5–1 mm, almost equal or slightly enlarged at the base, central, slender, terete, hollow, at first white overall, then brown (7E7–8, 8E7–8) toward the base, white pruinose above, villose to hispid below, attached to a white, appressed mycelial pad over the substratum. Lamellae adnexed to subcollariate, distant (14–18 reach the stipe), with 0–1 lamellulae, up to 1 mm broad, slightly intervenose, concolorous with the pileus; edges even, concolorous. Spore print pure white.

Micromorphological characteristics (Fig. 46): Basidiospores 9.2–10.4 × 3.7–4.3 μm (n = 34, Q = 2.41–2.48), ellipsoid, smooth, colorless, inamyloid, thin-walled. Basidia 26.4–37.3 × 6.4–8.8 μm, clavate, four-spored; basidioles clavate. Cheilocystidia 16–21.6 × 5–8.5 μm, forming a compact sterile edge, subclavate to irregularly shaped, with one or several finger-like appendages 2.4–4.2 μm wide, or shortly lobed or knobbed, colorless or pale melleous, inamyloid, thin-walled. Pleurocystidia none. Hymenophoral trama regular; element hyphae similar to those of the pileitrama. Pileipellis a hypotrichial layer (cutis) of subcylindrical cells 30–60 × 6–12 μm, often inflated, with orange (6B8) to brownish orange (6C8) walls up to 1 μm thick, encrusted with brownish orange (6C8) pigment, brownish red (11C8) in Melzer's reagent (dextrinoid); hairs of pileus 230–1200 × 4–7 μm, arising directly from the hypotrichium, repent or erect, cylindrical, tapering to an obtuse apex or with a broadly rounded apex, sometimes flexuous, smooth, brownish violet (11D8) to violet-brown (11E8) in Melzer's reagent (strongly dextrinoid), with colorless or pale melleous walls 1.6–3.2 μm thick, without a secondary septum. Hyphae of pileitrama 6–16 μm wide, parallel, cylindrical to subfusiform, often inflated, smooth, with pale melleous cytoplasmic pigments, brownish red (11C8) in Melzer's reagent (dextrinoid), thin-walled. Stipitipellis of fasciculate hairs arising from cutis hyphae; hairs of stipe similar to those of the pileus. Stipe trama composed of longitudinally running, cylindrical hyphae 5.3–8 μm wide, smooth, with pale melleous to brownish orange (6C8) cytoplasmic pigments, brownish red (11C8) in Melzer's reagent (dextrinoid), thin-walled. Clamps present in all tissues.

Habitat and phenology: Solitary or scattered on dead shrubs in evergreen broad-leaved forests, April to November, common.

Known distribution: Okinawa (Yaeyama Islands: Ishigaki Island and Iriomote Island), Malaysia (Kerekes and Desjardin 2009).

Specimens examined: KPM-NC0005014 (holotype), on dead twigs of various kinds of low trees in an evergreen broad-leaved forest, along the Urauchi River, Iriomote Island, Okinawa Pref., 2 Jun. 1999, coll. Takahashi, H.; CBM-FB-24120, same location, 1 Oct. 1996, coll. Takahashi, H.; CBM-FB-24121, same location, 15 May 1997, coll. Takahashi, H.; CBM-FB-24122, same location, 6 Jun. 1998, coll. Takahashi, H.; TNS-F-48181, on dead twigs of various kinds of low trees in an evergreen broad-leaved forest, Omoto-yama, Ishigaki-shi, Okinawa Pref., 9 Jun. 2012; KPM-NC0023876, on dead twigs of Ardisia quinquegona Blume, Banna-dake, Ishigaki-shi, Okinawa Pref., 2 Jun. 2013, coll. Takahashi, H.  

Japanese name: Shiraga-nise-houraitake.

Comments: This species is characterized by the radially sulcate-striate, canescent pileus colored brownish yellow at maturity; the white or brown, villose to hispid stipe attached by white, appressed mycelial pad to the substratum; the distant lamellae concolorous with the pileus; the subclavate or irregularly shaped cheilocystidia with one or several finger-like appendages; the dextrinoid hairs on the pileus and stipe; and the basidiome formation on dead twigs of various kinds of low trees in evergreen broad-leaved forests.

The lack of bright pigments, the relatively long (more than 7 mm) and central stipe, the ellipsoid basidiospores less than 9 μm wide, and the absence of pleurocystidia suggest that this species belongs in the genus Crinipellis, section Crinipellis, subsection Crinipellis (Singer 1942, 1986).

  Within the subsection, C. canescens appears to be closely related to several neotropical taxa that have a small pileus (less than 10 mm) and cheilocystidia with several appendages, such as Crinipellis pseudostipitaria Singer (Pegler 1983; Singer 1942), Crinipellis septotricha Singer (Pegler, 1983; Singer 1942), and Crinipellis stupparia (Berk. & M.A.Curtis) Pat. (Pegler 1983). The latter three taxa are distinct in having a pileus with a dark papillate umbo and in lacking a basal mycelium. Moreover, C. pseudostipitaria grows on grass debris, and C. septotricha and C. stupparia form hairs with secondary ladder-septations. Crinipellis canescens is also similar to Crinipellis omotricha (Berk.) D.A. Reid, redescribed by Pegler (Pegler 1986) from material collected in Sri Lanka, except that the latter has simple cheilocystida and a graminicolous habitat. Crinipellis hepatica Corner (Corner 1996), recently described from Malaysia, appears to be the closest ally. Unlike C. canescens, however, the former has a reddish brown pileus, an insititious stipe, subfusiform basidiole, and subventricose to subfusiform cheilocystidia without appendages.

Based on the ITS sequence data for the Malaysian C. canescens materials, Kerekes and Desjardin (Kerekes and Desjardin 2009) proposed relegating the species to the anamorphic genus Moniliophthora (Evans et al. 1978; Aime and Phillips-Mora 2005). 

References 文献

Aime MC, Phillips-Mora W. 2005. The causal agents of witches’ broom and frosty pod rot of cacao (chocolate, Theobroma cacao) form a new lineage of Marasmiaceae. Mycologia 97 (5): 1012–1022.

Corner EJH. 1996. The agaric genera Marasmius, Chaetocalathus, Crinipellis, Heimiomyces, Resupinatus, Xerula and Xerulina in Malesia. Beih Nova Hedwigia 111: 1–175.

Evans HC, Stalpers JA, Samson RA, Benny GL. 1978. On the taxonomy of Monilia roreri, an important pathogen of Theobroma cacao in South America. Can J Bot 56 (20): 2528–2532.

Kerekes JF, Desjardin DE. 2009. A monograph of the genera Crinipellis and Moniliophthora from Southeast Asia including a molecular phylogeny of the nrITS region. Fung Diver 37: 101–152.

Pegler DN. 1983. Agaric flora of the Lesser Antilles. Kew Bull, Addit Ser 9: 1–668.

Pegler DN. 1986. Agaric flora of Sri Lanka. Kew Bull, Addit Ser 12: 1–519.

Singer R. 1942. A monographic study of the genera Crinipellis and Chaetocalathus. Lilloa 8: 441–534 (published in 1943).

Singer R. 1986. The Agaricales in modern taxonomy, 4th edn. Koeltz, Koenigstein.

Takahashi H. 2000. Three new species of Crinipellis found in Iriomote Island, southwestern Japan, and central Honshu, Japan. Mycoscience 41 (2): 171–182.