Online publication; available at: http://jats-truffles.org/truffology/

Truffology 2 (1): 6–9 (2019)

Original peer-reviewed article （原著論文 ； 査読有）

A sporocarpic species of Glomeromycotina, Glomus radiatum new to Japan
胞子果性グロムス亜門の日本新産種 Glomus radiatum
Kohei Yamamoto1*, Yusuke Takashima2, Mai Suyama3, Teruhisa Masaki4, Yousuke Degawa5
山本 航平 1*, 高島 勇介 2, 陶山 舞 3, 正木 照久 4, 出川 洋介 5
1Tochigi Prefectural Museum, 2-2 Mutsumi-cho, Utsunomiya-shi, Tochigi 320-0865, Japan
栃木県立博物館，〒 320-0865 栃木県宇都宮市睦町 2-22College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan
茨城大学農学部， 〒 300-0393 茨城県稲敷郡阿見町中央 3-21-1

3Kanagawa Prefectural Museum of Natural History, 499 Iryuda, Odawara, Kanagawa 250-0031, Japan
神奈川県立生命の星 ・ 地球博物館， 〒 250-0031 神奈川県小田原市入生田 499

4Natural Product Frontier Research Lab., Taiho Pharmaceutical Co., LTD, 3 Ookubo, Tsukuba-shi, Ibaraki 300-2611, Japan
大鵬薬品 ・ 天然物フロンティア研究所， 〒 300-2611 つくば市大久保 3

5Sugadaira Research Station, Mountain Science Center, University of Tsukuba, 1278-294 Sugadaira Kogen, Ueda-shi,Nagano 386-2204
筑波大学山岳科学センター菅平高原実験所， 〒 386-2204 長野県上田市菅平高原 1278-294* Corresponding author （主著者）
E-mail: kohei081@yahoo.co.jp

Abstract
Glomus radiatum, a large sporocarp-forming species of Glomeromycotina, was collected from Gunma Prefecture. Overall the characteristics of sporocarp and spore are identical to description of the North American specimens including
holotype. This is the first record of G. radiatum from Asia.

要旨
大型の胞子果を形成するグロムス亜門の一種、 Glomus radiatum が群馬県内で採集された。 日本産標本の胞子果構造および胞子の特徴はホロタイプを含むアメリカ産標本およびカナダ産標本の記載と合致した。 本報告はアジアにおける G. radiatum の初記録である。
Article Info: Submitted: 14 December 2018

Accepted: 23 February 2019

Introduction

Published: 28 March 2019

species in Glomeromycotina form putative asexual spores

Glomeromycotina belongs to Mucoromycota that is the sister(i.e., conventionally named chlamydospore or azygospore),clade of Dikarya including Basidiomycota and Ascomycota

individually in rhizosphere without sporocarp formation(Spatafora et al., 2016). All the species in this subphylum(Błaszkowski, 2012; Schüßler & Walker, 2010; Yao et al., 1996).

but Geosiphon pyriforme (Kütz.) F. Wettst., which forms

However, this subphylum also includes sporocarpic species

endosymbiosis with cyanobacteria, are considered to bewhose sporocarps are several millimeters to tens of millimeters

a mycobiont of various land plants forming arbuscularin diameter (Gerdemann & Trappe, 1974; McGee, 1986). Thesemycorrhizae within plant roots (Smith & Read, 2008). Most

sporocarpic species are traditionally regarded as truffle-like fungi

6© The Japanese Association for Truffle Science (JATS), 2019

Yamamoto et al. : Glomus radiatum new to Japan

Truffology - Volume 2, Issue 1, 2019
cottony (Fig. 1A, B). Peridium undeveloped but a thin layer(Pegler et al., 1993; Tulasne & Tulasne, 1851).
Until now, the truffle-like sporocarp formation has been

composed of interwoven, aseptate, thin-walled, filamentous

reported from several genera, e.g., Glomus (e.g., G. macrocarpum

hyphae present. Gleba developed on peripheral region of basal

Tul. & C. Tul.), Rhizophagus (e.g., R. fasciculatus (Thaxt.) C.

sterile region of sporocarp, darker toward the sterile base (Fig.

Walker & A. Schüßler), and Sclerocystis (e.g., S. coremioides1B). Hyphae of sporocarp hyaline, thin-walled, aseptate, 1.5–5.3

Berk. & Broome) in Glomerales (Gerdemann & Trappe, 1974;

μm in width (Fig. 1D, E), sometimes forming terminal swelling

Thaxter, 1922), and Acaulospora (e.g., A. sporocarpia S.M.

up to 20 μm in diam in outermost part of sporocarp, (Fig. 1D).

Berch), Diversispora (e.g., D. epigaea (B.A. Daniels & Trappe)

Spore radially distributed, thin-walled younger ones embedded

C. Walker & A. Schüßler), and Redeckera (e.g., R. fulvum (Berk.

in exterior and thick-walled ones in interior (Fig. 1C), surface& Broome) C. Walker & A. Schüßler) in Diversisporales (Berch,smooth, light yellow-brown, ellipsoidal to broadly ellipsoidal,

1985; Daniels & Trappe, 1979; Redecker et al., 2007; Schüßler

55–87 μm in length, 44–55 μm in width, mean 68 × 50 μm (n =& Walker, 2010). Some of the sporocarpic species are suggested20), Q = 1.2–1.6, mean 1.4 (n = 20), often containing pale yellow

to be cosmopolitan (e.g., G. macrocarpum and G. microcarpumsingle large droplet up to 22 μm in diam and many small droplets

Tul. & C. Tul., from Europe, North America, and Australia [Berch(Fig. 1F). Spore wall composed of single layer, 4.6–8.1 μm in& Fortin, 1984b; Gerdemann & Trappe, 1974; McGee & Trappe,thickness. Subtending hyphae single; boundary between spore

2002; Tulasne & Tulasne, 1851]). On the other hand, diversity

and subtending hyphae occluded by wall thickening (Fig. 1F).

and distribution of sporocarpic species of Glomeromycotina areSpecimens examined: JAPAN, Gunma Prefecture, Numata-shi,

still under investigation in Japan; only S. coremioides has been

Tanbara kogen, N 36.787027, E 139.061407, alt. 1183 m, on litter

reported from the Kanto District (Degawa, 2001).

surface in a moor, 29 Jul. 2018, Y. Degawa, KPM-NC 26800.

Since 2017, zygomycetous flora of Gunma Prefecture has been

Notes: Morphological characteristics of the Japanese specimen

investigated (Degawa, 2018). During the course of a field survey

are almost identical to those in the original description from theof myxomycetes (2018 summer field excursion of the JapaneseNortheast (Thaxter, 1922) as well as the descriptions from theSociety of Myxomycetology), a sporocarp of G. radiatum

Pacific Northwest (Gerdemann & Trappe, 1974) in USA and from(Thaxt.) Trappe & Gerd. was collected from Numata-shi, Gunma

Quebec in Canada (Berch & Fortin, 1984a). This is the first report

Prefecture in July 2018. Brief description of its morphology isof G. radiatum from Asia. Glomus radiatum is also reported fromgiven bellow.

Austria (Palmer, 1997); however, the morphological description ofthis specimen is too brief to conclude the identity to the JapaneseMaterials and methods

specimen.

Hand-cut sections of dried specimen were mounted in 3%

The most distinctive character of this species among sporocarpic

KOH and observed under light microscope (OPTIPHOTO,species is a radial arrangement of spores in sporocarp. The

Nikon, Tokyo, Japan). All measurements were performed with

spores start to mature at the base of the sporocarp (Fig. 1C). This

PhotoRuler 1.1.3 (http://inocybe.info/). The terminology of Yao

centrifugal development pattern of the sporocarp was consistentet al. (1996) was adopted for the description. Dried specimen

with the previous report mentioned by Berch & Fortin (1984a).

was deposited in the Kanagawa Prefectural Museum of NaturalHyphal swellings observed around the surface zone of sporocarp

History (KPM) in Japan.

were putatively an initial stage of spore development that wasalso described in previous studies (Berch & Fortin, 1984a;

TaxonomyThaxter, 1922). However, those swellings were not described inGlomus radiatum (Thaxt.) Trappe & Gerd., Mycologia Memoirs

Gerdemann & Trappe (1974). In addition, a hyphal intrusion to5: 46, 1974.

spore observed on several specimens in North America (Berch≡ Endogone radiata Thaxt., Proceedings of the American& Fortin, 1984a; Gerdemann & Trappe, 1974) was not foundAcademy of Arts and Sciences 57: 316, 1922.

in the Japanese specimen and type specimen (Gerdemann &Fig. 1.

Trappe, 1974; Thaxter, 1922). Both morphological comparison

Sporocarp epigeous on litter surface, reniform, ca. 3 mm inand phylogenetic study based on a number of Japanese and Northwidth, ca. 2 mm in height, not containing the foreign matter,

American specimens are necessary to determine whether those

without exuding latex, surface white or greyish-white, slightlyspecimens are conspecific.

© The Japanese Association for Truﬄe Science (JATS), 20197

Truffology - Volume 2, Issue 1, 2019

Yamamoto et al. : Glomus radiatum new to Japan

Fig. 1. Glomus radiatum collected from Gunma Prefecture, Japan. A: Sporocarp. B: Sectioned sporocarp. Radially embedded brown spores and a sterile base are shown. C:
Magnified image of cross section of sporocarp. Thin-walled younger spores embedded in exterior (above) and thick-walled ones in interior (below) are shown. D: Hyphae ofsurface zone of sporocarp. Arrow indicates swollen hyphal tip. E: Hyphae of inner zone of sporocarp. F: Spores. Bars: C = 100 μm; D–F = 50 μm.
図 1． 群馬県産 Glomus radiatum． A ： 胞子果． B ： 胞子果断面． 放射状に配列する褐色を帯びた胞子と無性基部を示す． C ： 胞子果断面 （拡大）． 基部 （下部）に成熟した厚壁の胞子が， 縁部 （上部） に未熟な薄壁の胞子が存在する様子を示す． D：胞子果表面の菌糸とその先端の肥大部 （矢印）． E：胞子果内部の菌糸．
F ： 胞子． スケール ： C 100 µm; D–F 50 µm.

According to Gerdemann & Trappe (1974), G. radiatum wasproved as an arbuscular mycorrhizal fungus associated with

us an opportunity to field survey in Gunma Prefecture, and Mr.
Muneyuki Ohmae for supporting microscopic observation.

Cupressus nootkatensis D. Don (Cupressaceae) by the observationof a direct attachment of sporocarps to the plant root. Thujopsis

References

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