KEY WORDS: Sclerocystis, S. sinuosa, S. coremioides, S. clavispora, S. taiwanensis, S. liquidambaris, S. rubiformis, dichotomous key.

Six species of Sclerocystis (S. clavispora, S. coremioides, S. liquidambaris, S. rubiformis, S. sinuosa, and S. taiwanensis) from Taiwan are described and illustrated, and a key to species is provided. Spores of these species were assigned to one of three size-classes based on an area index calculated by multiplying length x width: 1000-3000 mm2, 6000-8000 mm2, and intermediate sized spores. Sclerocystis clavispora and S. liquidambaris formed large and small spores, sometimes in the same sporocarp. Sclerocystis rubiformis and S. taiwanensis mostly produced smaller spores; however, the spore size of S. sinuosa and S. coremioides were mainly intermediate between smaller and larger spore groups.

The genus Sclerocystis was recently emended on the basis of comparative studies of spore ontogeny and sporocarp morphology (Wu, 1993). Sufficient evidence resulted from that study to retain Sclerocystis sensu Gerdemann and Trappe (1974) as distinct from Glomus. The suggestion by Almeida and Schenck (1990) to synomize all but one species of Sclerocystis with Glomus was not accepted. The emended description reads, "sporocarps globose or subglobose or hemispherical, enclosed by a peridium or naked, with a multihyphal stipe or monohyphal stalks; chlamydospores arranged side by side in a single layer, radiating out from a central plexus of hyphae; central plexus composed of a broad, stellate thick-walled cell or interwoven hyphae; development of chlamydospores within sporocarps synchronous or asynchronous; sidebranches frequently produced from the base of chlamydospores, becoming spores or intersporal hyphae". go back to the top

During an investigation of arbuscular mycorrhizal fungi in Taiwan, numerous sporocarps of Sclerocystis were isolated by a wet-sieving and decanting method (Gerdemann and Nicolson, 1963). The sporocarps were further purified by sucrose centrifugation (Jenkins, 1964). Sporocarps and spores were mounted in Hoyer's medium and made into semipermanent slides. Some sporocarps were also preserved in FAA fixative. Specimens are deposited in the Soil Microbiology Lab, Agricultural Chemistry Department, Taiwan Agricultural Research Institute, Wu-feng, Taichung, Taiwan, R.O.C. and Mycological Herbarium, Department of Plant Pathology, University of Florida, Gainesville, Florida, U. S. A.

In this study, some species of Sclerocystis produce spores in two different sizes (large and small). Since spores of Sclerocystis mostly are elliposoid to clavate, their outer figures in optical section side view are measured as rectangles. Therefore, spore size is determined by an area index calculated by multiplying length and width. The distribution curve of spore size in each species is depicted by area indices and their frequency.

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Sporocarps globose, subglobose, brown to blackish brown, 300-600 x 400-700 mm, without peridium, usually with one to four monohyphal stalks; chlamydospores brown to dark brown, radially arranged on a central plexus, developed synchronous, or asynchronous, clavate to subcylindric, 22.5-75 x 47.5-157.5 mm; spore wall usually thickened at apex, up to 40 mm.

Collections examined: 1. Taiwan: Chi-tou, from rhizosphere of Chimonobambusa quadrangularis (Fenzi) Markino, Wu-850821; 2. Taiwan: Chi-tou, from the rhizosphere of Erechthites valerianifolia (Walf.) DC., Wu-8508201; 3. Taiwan: Chi-tou, from the rhizosphere of Gingo biloba L., Wu-8508202; 4. Taiwan: Chi-tou, from the rhizosphere of Colocasia formosanum Hayata, Wu-8607151; 5. Taiwan: Kenting, from the rhizosphere of Colocasia formosanum, Wu-8605171; 6. Taiwan: Pintong, from the rhizosphere of asparagus (Asparagus officinalis L.), Wu-860813; 7. Taiwan: Wu-feng, Taichung, from the rhizosphere of rice (Oryza sativa L.), Wu-920717.

notes: Sclerocystis clavispora produces two distinctly different sized spores: one large (7000-8000 mm2) and the other small (2000-3000 mm2)(Fig. 19A). Both types of spores could be found in the same sporocarp or in different sporocarps isolated from the same rhizosphere. The sporocarps producing smaller spores formerly were identified as S. microcarpus (Iqbal and Bushra, 1980).

Chlamydospores sometimes developed asynchronously. In the same sporocarp, club-shaped vesicles (young spores) were often observed intermingled with mature, thick-walled spores (Fig. 4). Obviously, spore walls were thickened gradually at the apex and base. However, the factor which triggers the process of wall thickening is still unknown. It might be closely related to the production of two types of spores. go back to the top

2. Sclerocystis coremioides Berk. & Bromme, J. Linn. Soc. London 14:137, 1873.

= Xenomyces ochraceus Cesati, Atti R. Accad. Sci. Fisiche e Math. Napoli 8:26, 1878.

= Ackermannia coccogena Pat., Bull. Soc. Mycol. France 18:183, 902.

= Sphaerocreas coccogena (Pat.) van Hohn, Sitzungsber. Kaiserl. Akad. Wiss. Wien Math.-Naturwiss. Kl. Abt. I. 118:401, 1909.

= Sclerocystis coccogena (Pat.) von Hohn., Sitzungsber. Kaiserl. Akad. Wiss. Wein Matn.-Naturwiss. Kl. Abt. I.119:399, 1910.

= Ackermannia dussii Pat., Bull. Soc. Mycol. France 18:180-181, 1902.

= Spherocreas dussii (Pat.) von Hohn., Stizungsber. Kaiserl. Akad.Wiss. Wien Math.-Naturqiss. Kl. Abt. I. 118:401, 1909.

= Scelerocystis dussii (Pat.) von Hohn., Sitzungsber. Kaiserl. Akad. Wiss. Wein Math.-Naturwiss. Kl. Abt. I.119:399, 1910.

= Spherocreas javanicum von Hohn., Sitzungsber. Kaisherl. Akad. Wiss. Wien Math.-Naturwiss. Kl. Abt. I. 117:1014-1015, 1908.

= Endogne minutissima Beeli, Bull. Soc. Roy. Bot. Belg. 56:57, 1923.

Sporocarps brown or yellow brown, 200-250 x 450-550 mm, subglobose or pulvinate, with or without multihyphal stipes, usually flattened at base; chlamydospores arranged radially in a hemispherical layer, ellipsoid, ovoid, triangular, or oblong ellipsoid to clavate, yellow brown, (35-) 45-65 (-70) x 50-80 (-90) mm; spore wall 1.5-2.5 mm and frequently thicked at base, up to 6 mm; subtending hypha long, single, occasionally two, 5-6 mm at attachment, then tapered to 7.5 mm broad; plexal hyphae broad, 6-12.5 mm; peridial hypha, thick-walled, 2.5-5 mm, sometimes with sparse septum.

Collections examined: 1. Taiwan: Tainan, from rhizosphere of Ageratum conyzoides L., Wu-850725; 2. Taiwan: Tainan, from the rhizosphere of orange (Citrus sp.), Wu-8608141; 3. Taiwan: Taipei, from the rhizosphere of Bignonia sp., Wu-850810; 4. Taiwan: Chi-tou, from the rhizosphere of Colocasia formosanum, Wu-8607152; 5. Taiwan: Pintong, from the rhizosphere of asparagus (Asparagus officinalis), Wu-860813; 6. USA: Oregon, F55365.

notes: Sporocarps collected in this study were seldom formed in rows. They exist as a thin layer, or single fruit body on soil, in agreement with the description of Jao et al. (1992). Sporophores produced from the bases of attached hyphae were very common; however, the septum below the spore base was not formed frequently as described by Almeida and Schenck (1990). go back to the top

3. Sclerocystis liquidambaris Wu & Chen, Trans. Mycol. Soc. Rep. China 2:73-83, 1987.             = Sclerocystis cunninghmia Hu, Quart. J. Chinese For. 21(2):45-72. 1988.

Sporocarps globose to subglobose, 300-600 x 370-680 mm, brown to dark brown, consisting of chlamydospores formed radially within the "paraphysis-like" structures. "Paraphysis-like" structures cylindrical, clavate to spathulate, yellow brown to dark brown, thick-walled, up to 200 mm long, protruding from the central plexus of hyphae or from the spore base. The apices of "paraphysis-like" structures tightly packed, forming a peridium enclosing the whole sporocarp. Chlamydospores cylindro-clavate to obvoid, (27.5-) 40-65 (-75) x (50-) 72.5-132.5 mm, brown to reddish brown, sometimes with a septum at the spore base.

Chlamydospore walls brown to reddish brown, 7.5-25 mm thick at their apices, 6-10 mm thick at the base, and 2-5 mm thick at the sides. Sometimes, hyaline, thick-walled (up to 6 mm thick) structures with a membraneous outer coat are present within the chalmydospores.

Collections examined: 1. taiwan:Taipei, Holotype, from the rhizosphere of Liquidambar formosana Hance, Wu-860203; 2. taiwan:Taipei, Isotype, Wu-860627; 3. TAIWAN:Taipei, Paratype, Wu-860627; 4. TAIWAN: Kao-shiung, Liou-Kuei, from the rhizosphere of Cunninghamia lanceolata (Lamb.) Hook, Wu-870117.

notes: Sclerocystis liquidambaris produces two sizes of chlamydospores similar to those of S. clavispora (Fig. 19A). Spore size falls into two major categories, one 6000-7000 mm2 and the other 2000-3000 mm2. Sclerocystis liquidambaris differs from S. clavispora mainly by its "paraphysis-like" structures which protrude out of sporal layer and form a "pseudoperidium". This species was also found in Korea (Koo et al., 1992; Eom et al., 1992). go back to the top

4. Sclerocystis rubiformis Gerdemann & Trappe, Mycologia Memoir No. 5:60-63, 1974.            = Sclerocystis indicus Bhattacharjee, Mukerji & Misr. Acta Botanica Indica 8:99-100, 1980.

= Sclerocystis pachycaulis Wu & Chen, Taiwania 31: 74-75, 1986.

Sporocarps yellow to yellow brown, globose to subglobose, 150-300 x 190-360 mm. In young sporocarps, chlamydospores are arranged in a hemispherical layer. However, with the subsequent formation of additional chlamydospores, these immature sporocarps are transformed into globular sporocarps with radially arranged chlamydospores. Chlamydospores are arranged on a thick-walled central plexal cell which is connected with a broad hyphal stalk. Perdium unknown. Chlamydospores yellow to yellow brown, obovoid to ellipsoid, sometimes irregular, 27.5-60 x 37.5-87.5 mm. Chlamydospore wall yellow-brown, 1-5(-7.5) mm thick, with a hyaline, separable outer layer, 0.5-1 mm thick. Usually chlamydospore contents separated by 1-2 adventituous septa below the region of attached hypha. Attached hyphae 7.5-15 mm diam, sometimes with a thick wall up to 7.5 mm that tapers for some distance.

Collections examined: 1. TAIWAN: Chi-tou, from the rhizosphere of Gonostegia hirta (Blume) Miq., Wu-043; 2. TAIWAN: Chi-tou, from the rhizosphere of Polygonum hydropiper L., Wu-044; 3. TAIWAN: Chi-tou, from the rhizosphere of Phyllostachys pubescens Mazel, Wu-045; 4. TAIWAN: Chi-tou, from the rhizosphere of Microstegium geniculatum (Hayata) Honda, Wu-046; 5. TAIWAN: Chi-tou, from the rhizosphere of Asplenium normales Don., Wu-047; 6. TAIWAN: Chi-tou, from the rhizosphere of Erechthites valerianifolia, Wu-8508203; 7. TAIWAN: Chi-tou, from the rhizosphere of Gingo biloba, Wu-8508204; 8. TAIWAN: Chi-tou, from the rhizosphere of Colocasia formosanum, Wu-8607153; 9. TAIWAN: Kenting, from the rhizosphere of Colocasia formosanum, Wu-8605172.

notes: Spores of this species are in the same size range as those produced by S. taiwanensis (Fig. 19B). The plexal hypha of S. rubiformis is a broad, thick-walled cell around which spores are produced and is different from that of S. taiwanensis because the latter plexal hypha is formed by the fusion of more than one monohyphal stalk. Another similarity between S. rubiformis and S. taiwanensis is that their spores are enclosed by a separable hyaline outer layer. This species has been maintained in pot culture of ACT. go back to the top

5. Sclerocystis sinuosa Gerdemann & Bakshi, Trans. Br. Mycol. Soc. 66:340-343, 1976.

= S. pakistanica Iqbal & Bushra, Trans. Mycol. Soc. Japan 21:59-60, 1980.

Sporocarps reddish-brown to dull brown, globose to subglobose, 248-580 x 380-650 mm. Peridium tightly enclosing a sporocarp, composed of thick-walled interwoven hyphae. In the younger collections ( i.e., spores containing numerous oil droplets and spore wall usually evenly thickened), peridial hyphae sinuous. In the older collections ( i.e., spores with much less cellular contents, often infected by other fungi, perforated, and spore wall often thickened at apex or lateral side ), sinuous feature may appear indistinct. Chlamydospores (22.5-) 35-74 (-87.5) x (47.5-) 55-125 (-145) mm, globose, subglobose, obovoid, ellipsoidal, clavate, or irregular, wall single, with walls either evenly thickened or unevenly thickened, usually thickened at the apex or lateral side, (1.5-) 5-22.5 (-30) mm, with 1-2 attached hyphae. Chlamydospores often infected by other soil microorganisms and "Glomus-like" endospores also frequently formed inside.

Collections examined: 1. taiwan: Tainan, Anpin; from the rhizosphere of Miscanthus sp. in Casuarina equisetifolia L . woods, Wu-850725; 2. taiwan: Tainan, Anpin; from the rhizosphere of ground covers in C. equisetifolia L. woods, Wu-850918; 3. taiwan: Pintong, by Kau-ping River; from the rhizosphere of legume (Glycine sp.), Wu- 860814 a; 4. taiwan: Pintong, by Kau-ping River; from the rhizosphere of asparagus (A. officinalis), Wu-860813; 5. taiwan: Pintong, Tongang; from the rhizosphere of unidentified herb grass, Wu-ME2; 6. taiwan: Tainan, Charlu; from the rhizosphere of orange (Citrus sp.), Wu-860814 b; 7. taiwan: Nantou, Chi-tou, from the rhizosphere of Sinocalamus sp., Wu-850814; 8. taiwan: Taichung, Wu-feng, from the rhizosphre of maize (Zea mays L.), Wu-111401; 9. taiwan: Orchid Island, Taitung, from the rhizosphere of C. equisetifolia, Wu-860707; 10. U.S.A., invam collection, Gainesville, Florida (SSNS 122).

notes: The indistinct sinuous feature of the peridium of mature sporocarps and the thickened peridium may lead to confusion in identifying this species. Sclerocystis pakistanica was described from such materials. Spores with unevenly thickened walls are frequently found in the sporocarps isolated from crop fields or beach sand dunes. The bore holes and internal projections of spore wall (Fig. 17) are probably caused by fungi and actinomycetes (Lee, 1991). Sporocarps usually arise from two to four monohyphal stalks (Wu, 1993). The heterogenous spores with uneven wall thickness and indistinct sinuous feature have been illustrated by Wu and Chen (1993). go back to the top

6. Sclerocystis taiwanensis Wu & Chen, Trans. Mycol. Soc. Rep. China 2: 73-83, 1987.

Sporocarps reddish brown, brown or dark brown, globose, subglobose or ellipsoidal, 200-300 x 180-280 mm, with chlamydospores formed radially in a single, tightly packed layer around a central plexus of hyphae. Peridium lacking. Chlamydospores 40-85(-105) x (17.5-)22-42.5(-55) mm, clavate, cylindro-clavate, triangular or irregular, with or without a septum at the spore base. Chlamydospore wall laminate or single, with a hyaline, separable outer layer (ca. 1 mm), yellow, yellow- brown, sometimes olive-brown, (4-)7.5-22.5(-25) mm thick at the apex, 1.5-5 mm thick at the sides, generally thickest at the apex.

Collections examined: 1. taiwan: Chi-tou, Holotype, from the rhizosphere of Crassocephalum rabens (Juss. ex Jacq.) S. Moore, Wu-8508205; 2. taiwan: Chi-tou, from the rhizosphere of Colocasia formosanum, Wu-8607154; 3. taiwan: Taipei, from the rhizosphere of unknown host, Wu-850810; 4. taiwan: Tainan, from the rhizosphere of orange (Citrus sinensis Osb.), Wu-850724.

notes: Sclerocystis taiwanensis is very similar to S. rubiformis. However, the spores of former species are tightly packed around a central plexus which is formed by the fusion of more than one monohyphal stalk. Spores of the latter are only loosely arranged around a broad, thick-walled stellate cell. Sclerocystis taiwanensis was recently isolated from Korea (Koo et al., 1992; Eom et al., 1992) and Philippines (personal communication). go back to the top

The evolutionary affinities among these six species has been previously described (Wu, 1993). Sporocarps of S. rubiformis are considered primitive, due to their lack of a peridium and producing sporocarps from a simple, broad, thick-walled plexal cell. In the naked sporocarps of S. taiwanensis, the central plexus is more complicated than that of S. rubiformis and is formed by the fusion of more than one monohyphal stalk. Sclerocystis clavispora produces sporocarps similar to S. taiwanensis, but the central plexus is replaced by interwoven hyphae and is thought to be advanced to S. taiwanensis. Sclerocystis liquidambaris appears to be derived from the S. clavispora/S. taiwanensis type, with the hyphal branches arising from the base of the spores becoming thick-walled. The peridium of S. liquidambaris is thought primitive if compared with that of S. sinuosa and S. coremioides, since it is only tightly packed by thick-walled, clubshaped cells. In the sporocarps of S. sinuosa and S. coremioides, however, a peridium of interwoven hyphae is well developed. Sclerocystis sinuosa has a number of monohyphal stalks radiating out of sporocarps. The monohyphal stalks of S. coremioides are combined into a coarse stipe. A single monohyphal stalk has the ability to produce a broomlike fruiting body, and further develops into a globose sporocarp. However, the fusing of many monohyphal stalks into a stipe would result in a loss of the ability to produce spores in a globular arrangement, but finally producing a hemispherical sporocarp.

In this monograph, the spore area (length x width)/frequency diagrams for these six species (Fig. 20) show that (i) S. rubiformis and S. taiwanensis consistently produce small spores (Fig. 19B), (ii) S. clavispora and S. liquidambaris produce spores mainly in two different sizes (smaller and larger) (Fig. 19A), and (iii) S. sinuosa and S. coremioides produce mostly medium sized spores (Fig. 20). These results are thought to support previous suggestions that S. rubiformis and S. taiwanensis are the most primitive species, because (a) their sporocarps are very simple, small, and not enclosed by peridium, and (b) they produce smaller spores. The sporocarp structures of Sclerocystis clavispora and S. liqudiambaris are more advanced than S. rubiformis and S. taiwanensis, and tend to produce larger spores. Since both are in a transitional stage connecting the primitive S. rubiformis/S. taiwanensis group and advanced S. sinuosa/S. coremioides group, they produce both smaller and larger spores. The sporocarps of S. liquidambaris are enclosed by "paraphysis-like" structures which result in limited space for sporulation; therefore, the number of smaller spores is comparatively fewer than S. clavispora. Sclerocystis sinuosa and S. coremioides are highly advanced species and have vigorous ability to produce spores. Due to the presence of a peridium and the influence of limited space in the sporocarp, sporulation is constrained and most of the spores produced are of a medium size. However, the spore size of S. coremioides was closer to that of S. rubiformis and S. taiwanensis, because all of the monohyphal stalks were already fused into a hyphal stipe and thus, it has lost the ability to produce more and larger spores. Some species of Sclerocystis are only isolated from non-disturbed areas, such as S. rubiformis and S. taiwanensis which are found in natural reservations. Sclerocystis coremioides and S. sinuosa are widely distributed in Taiwan. go back to the top

1. Sporocarps not enclosed in a peridium........................................................................2

1. Sporocarps enclosed in a peridium...............................................................................4

2. Sporocarps with a monohyphal stalk; chlamydospores raidally arranged on a broad, thick-walled plexal cell.........................................................S. rubiformis

2. Sporocarps with more monohyphal stalks; plexus not a broad, thick- walled cell; chlamyspores thightly arranged side by side....................................................................3

3. Sporocarps relatively small, <300 mm; chlamydospore with a separable hyaline outer wall............ ..........................................................................S. taiwanensis

3. Sporocarps large up to 800 mm; chlamydospore without a separable hyaline outer wall..........................................................................................S. clavispora

4. Peridium composed of a layer of club-shaped cells.....S. liquidambaris

4. Peridium composed of interwoven hyphae.........................................5

5. Sporocarps not hemispherical; peridium showing sinuous feature; if indistinct, spores with varialbe thickness........................................................................S. sinuosa

5. Sporocarps hemispherical, with a hyphal stalk which may connect into a column or branched appearance ......................................S. coremioides  go back to the top

ACKNOWLEDGEMENT

This research was financially supported by The National Science Council of Taiwan, Republic of China (NSC 82-0409-B-055-013). Appreciation is extended to Drs. R. E. Koske, James W. Kimbrough, and G. L. Benny for their critical reviews of this manuscript and for providing specimens used in this research.

LITERATURE CITED

Almeida, R. T. and N. C. Schenck. 1990. A revision of the genus Sclerocystis (Glomaceae, Glomales). Mycologia 82:703-714.

Eom, A.-H., S.-K. Lee, and S.-S. Lee. 1992. Five sporocarpic species of Glomus found in Korea. Korean Mycol. 20: 85-94.

Gerdemann, J. W. and B. K. Bakshi. 1976. Endogonaceae of India: Two new species. Trans. Br. Mycol. Soc. 66:340-343.

Gerdemann, J. W. and T. H. Nicolson. 1963. Spores of mycorrhizal Endogone species extracted from soil by wet-sieving and decanting. Trans. Br. Mycol. Soc. 46:235-244.

Gerdemann, J. W. and J. M. Trappe. 1974. The Endogonaceae in the Pacific Northwest. Mycologia Memoir No. 5, 76p.

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Koo, Chang-Duck, T.-H. Kim, C.-K. Yi, W.-K. Lee, C.-H. Kang, B.-C. Lee, and S.-K. Lee. 1992. Sporocarp-forming arbuscular mycorrhizal fungi, Glomus spp. in forest soils of Korea. Korean Mycol. 20:29-36.

Lee, P. J. 1991. Seasonal dynamics of Gigaspora gigantea and associated microorganisms in a sand dune. Ph.D. thesis, The University of Rhode Island, Kingston, RI.

Smith, G. W. and N. C. Schenck. 1985. Two new dimorphic species in the Edogonaceae: Glomus ambisporum and Glomus heterosporum. Mycologia 77:566-574.

Trappe, J. M. 1977. Three new Endogonaceae: Glomus constrictus, Sclerocystis clavispora, and Acaulospora scrobiculata. Mycotaxon 6:359-366.

Wu, C.-G. 1993. Glomales of Taiwan: III. A comparative spore ontogeny in Sclerocystis (Glomaceae, Glomales). Mycotaxon 47:25-39.

Wu, C.-G. and Z. C. Chen. 1993. Observations of Sclerocystis sinuosa in Taiwan (Glomaceae, Glomales). Trans. Mycol. Soc. Japan 34(2): (in press).

Wu, C.-G. and Z. C. Chen. 1987. The Endogonaceae of Taiwan. II. Two new species of Sclerocystis from Taiwan. Trans. Mycol. Soc. Rep. China 2:73-83.

Wu, C.-G. and Z. C. Chen. 1986. The Endogonaceae of Taiwan. I. A preliminary investigation on Endogonaceae of bamboo vegetation at Chi-tou areas, Central Taiwan. Taiwania 31:65-88.

Yao, Y.-J., D. N. Pegler and T. W. K. Young. 1992. Revision of the type of Endogone alba (Endogonaceae). Mycotaxon 45:109-122.

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