Vinositunica radiata Koh. Yamam., Degawa & A. Yamada, sp. nov. FIG. 5
MycoBank number: MB 829986; Index Fungorum number: IF 829986; Facesoffungi number: FoF
Typification: JAPAN. OKINAWA: Okinawa-jima Isl., Kunigami-son, Mt. Nishimedake (26°48′02″N, 128°16′32″E), ca. 370 m a.s.l., epigeous in a forest of Castanopsis sieboldii subsp. lutchuensis with sparse Quercus miyagii, 14 Oct 2013, K. Yamamoto B-13004 (holotype KPM-NC0026742). DNA sequences ex-holotype: 18S = LC431090; 28S = LC431106; tef1 = LC431122; rpb1 = LC431146.
Diagnosis: The combination of a short sporocarp stipe and radial arrangement of red-wine-colored chlamydospores is not observed in other Endogonales species. Although radial arrangement of dark-colored chlamydospores is a characteristic of Glomus cuneatum sporocarps, the spore size of this species differs from that of V. radiata.
Etymology: radiata (Latin), referring to the radial spore arrangement.
Description: Sporocarp epigeous on the bare soil sur- face of the forest floor; reniform to pulvinate; 1.3–2.5 mm wide, 0.8–1.8 mm high; short stipe-like sterile base often present, 0.7–1.0 mm wide, 0.2–0.5 mm high; surface tomentose, white or pale yellow in immature stage, pale grayish-purple when mature; cut surface white in immature stage, grayish- purple when mature, not exuding latex, and not containing foreign matter. Peridium persistent, single- layered, white to pale grayish-purple, 78.5–125 μm thick; composed of loosely woven, somewhat fastigiate, trichoderm-like hyphae, 1.5–4 μm wide, somewhat thick-walled up to 1 μm thick, often aseptate. Gleba develop on periphery of the central sterile region of sporocarp, densely packed with chlamydospores; hyphae colorless, with radial arrangement from sterile region to surface, 1–5 μm wide, often aseptate, slightly thick-walled, up to 1.5 μm thick. Chlamydospore radially distributed, often broadly ellipsoidal or globose to ellipsoidal, (67–)68–85(–92.5) μm long, (49–)52.5–69 (–73) μm wide, mean size of 75.5 × 62 μm (Q = 1–1.4, Qm = 1.23, n = 21), surface smooth, pale yellow when immature, dark red-wine color when mature; wall com- posed of two layers, i.e., an outer dark red-wine-colored layer 1.5–3 μm thick and an inner colorless layer that is thicker than the outer layer, 4.5–5 μm thick; boundary between chlamydospore and subtending hyphae occluded by wall thickening. Chlamydosporic contents uniformly granular, up to 6.5 μm wide, yellow. Subtending hyphae single, tenacious, same color as outer layer of chlamydospore wall, 4.5–8.5 μm wide. In Melzer’s reagent, peridial and glebal hyphae stained reddish-brown (dextrinoid); outer layer of chlamydospore stained dark reddish-brown (dextrinoid); inner layer of chlamydospore showed almost no staining (inamyloid). Odor not distinctive.
Ecology and distribution: Epigeous on the ground of clay soil in forests dominated by Castanopsis sieboldii in a warm temperate–subtropical climate on the western part of Honshu Island and the Nansei Islands, Japan. Found in summer to autumn.
Other specimens examined: JAPAN. OKINAWA: Iriomote-jima Isl., Taketomi-cho, Urauchi-gawa River (24°21′42″N, 123°47′53″E), ca. 50 m a.s.l., on the ground of a roadside neighboring a C. sieboldii subsp. lutchuensis forest, 28 Jun 2018, K. Yamamoto B-18001 (KPM-NC0026745); Ishigaki-jima Isl., Ishigaki-shi, at the foot of Mt. Nosokodake (24°29′32″N, 124°14′37″E), ca. 15 m a.s.l., on the ground under a young C. sieboldii subsp. lutchuensis tree in a secondary forest dominated by nonectomycorrhizal Adinandra yaeyamensis and Bischofia javanica, 11 Oct 2013, K. Yamamoto B-13002 (KPM-NC0026740); Okinawa-jima Isl., Kunigami-son, Mt. Yonahadake (26°43′45″N, 128°12′48″E), ca. 330 m a.s.l., semihypogeous in a forest dominated by C. sieboldii subsp. lutchuensis with sparse Quercus miyagii, 13 Oct 2013, K. Yamamoto B-13003 (KPM- NC0026741); same locality, epigeous in a forest dominated by C. sieboldii subsp. lutchuensis, with sparse Q. miyagii, 13 Nov 2013, T. Orihara B-13005 (KPM- NC0026743); same locality as holotype specimen, 31 Aug 2014, K. Yamamoto B-14002 (KPM-NC0023961); Okinawa-jima Isl., Kunigami-son, Jashiki (26°46′05″N, 128°13′44″E), ca. 150 m a.s.l., epigeous in a forest dominated by Q. miyagii and C. sieboldii subsp. lutchuensis, 31 Aug 2014, K. Yamamoto B-14003 (KPM-NC0023962; duplicate TNS-F-70441); Okinawa-jima Isl., Kunigami- son, Mt. Ibudake (26°45′27″N, 128°17′41″E), ca. 170 m a. s.l., on the ground of a roadside under a young C. sieboldii subsp. lutchuensis tree, 1 Sep 2014, K. Yamamoto & H. Masuya B-14004 (KPM- NC0023963; duplicate TNS-F-70442); Kagoshima: Amami-oshima Isl., Amami-shi, Kinsakubaru (28°20′ 35″N, 129°27′17″E), ca. 200 m a.s.l., on the eroded ground of a riverside under a C. sieboldii subsp. lutchuensis tree, 27 Jun 2014, K. Yamamoto B-14001 (KPM- NC0026744); Kyoto: Fukuchiyama-shi, Naiku, Koudai- jinja (35°25′51″N, 135°09′16″E), ca. 115 m a.s.l., on the ground in a climax forest of C. sieboldii, 15 Jul 2013, K. Yamamoto B-13001 (KPM-NC0026739).
Notes: Whitish immature sporocarps contained colorless chlamydospores with yellowish oil globules (FIG. 5C). Outer wall of chlamydospores and sporocarp tissue when mature are dark red-wine in color (FIG. 5D, H, I) and pale purple (FIG. 5A, B), respectively. A short stipe-like sterile base was frequently observed (FIG. 5B, C), which is rare in Endogonaceae. Radial arrangement of spores (FIG. 5B) was characteristic of V. radiata. Glomus cuneatum described from Australia (McGee and Trappe 2002) shares the following characteristics with Vinositunica, in particular V. radiata: stipe-like sterile base present in sporocarp; spores radially arranged; spore wall blackish at outer surface and hyaline at inner surface; and yellowish viscid fluid is released when sporocarp was sectioned. However, G. cuneatum clearly differs from the two species of Vinositunica described in this study in that the chlamydospores of G. cuneatum are ovoid, clavate, or irregular in shape and 70 × 70–120 × 180 μm in size, and its sporocarp is fragmented into cuneate segments (McGee and Trappe 2002). Glomus radiatum, which has an uncertain position within Glomeromycotina (Schüßler and Walker 2010), also forms chlamydospores in a radial arrangement in the sporocarp. However, the spore wall of this species is light yellow, not red-wine-colored (Thaxter 1922; Gerdemann and Trappe 1974; Berch and Fortin 1984; Yamamoto et al. 2019). Although Endogone acrogena in Endogonaceae also shows radially arranged spores, this species is zygosporic and forms yellowish sporocarps (Gerdemann and Trappe 1974). Sporocarps were often found on the bare ground of clayey soils along trails in forests of C. sieboldii. Thus, V. radiata is likely an ectomycorrhizal mycobiont of Castanopsis.
Figure 5. Morphological characteristics of Vinositunica radiata. A–B. KPM-NC0023963. C. KPM-NC0026739. D, H. KPM-NC0026741. E, G. KPM-NC0023962. F, I. KPM-NC0026742. A, B. A sporocarp on the soil surface (A) and its cross-section (B), showing the radial arrangement of chlamydospores and stipe-like sterile base. C. Cross-section of an immature sporocarp on the soil surface, in which its yellowish contents of chlamydospores are visible due to the colorless outer spore wall. D, E. Cross-section of the surface zone of a sporocarp, showing chlamydospores and peridium mounted with lactoglycerol (E: stained with Melzer’s reagent). F. Chlamydospores and glebal hyphae, stained with Melzer’s reagent. G. Narrow, thick-walled glebal hyphae, stained with Melzer’s reagent. H, I. Chlamydospores. Bars: A–C = 1 mm; D–F = 100 μm; G–I = 50 μm.