Oidiodendron: A survey of the named species and related anamorphs of Myxotrichum

Adrianne V. Rice; Randolph S. Currah

STUDIES IN MYCOLOGY 53: 83–120. 2005. Oidiodendron: A survey of the named species and related anamorphs of Myxotrichum Adrianne V. Rice* and Randolph S. Currah Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9 Canada** *Correspondence: Arice@NRCan.gc.ca Abstract: Synoptic and dichotomous keys to 23 species of Oidiodendron and similar arthroconidial anamorphs of Myxotrichum were developed using morphological and physiological characters. Illustrations and brief descriptions based on living isolates and published descriptions are provided for all species treated. Included are the unnamed Oidiodendron states of Myxotrichum arcticum, M. cancellatum, M. emodense, M. setosum, and M. striatosporum, as well as the anamorphic species O. ambiguum, O. cerealis, O. chlamydosporicum (inclusive of O. scytaloides as a synonym), O. echinulatum, O. ﬁmicola, O. ﬂavum, O. fuscum, O. griseum, O. hughesii (inclusive of O. reticulatum as a synonym), O. maius (inclusive of O. maius var. citrinum and O. maius var. maius), O. muniellense, O. myxotrichoides, O. periconioides, O. pilicola, O. rhodogenum, O. setiferum (inclusive of O. ramosum as a synonym), O. tenuissimum, and O. truncatum. Oidiodendron fuscum, the original type species, is recognized as distinct. Oidiodendron robustum is excluded because of its large conidia and conidiophores and because the original drawings do not convincingly portray arthroconidia. Oidiodendron terrestre is excluded because its large, two-celled conidia, rapid growth, and hyaline conidiophores are inconsistent with the generic diagnosis and because the mode of its conidiogenesis is unclear from the original descriptions and illustrations. Taxonomic novelties: Oidiodendron maius var. citrinum (Barron) Rice & Currah stat. nov. Key words: dichotomous key, Myxotrichum, morphological characters, Oidiodendron, Oidiodendron fuscum, Oidiodendron maius var. citrinum, Oidiodendron maius var. maius, physiological characters, synoptic key. INTRODUCTION Species of Oidiodendron Robak and the anamorphs of Myxotrichum arcticum Udagawa, Uchiyama & Kamiya, M. cancellatum Phillips, M. emodense Udagawa & Uchiyama, M. setosum (Eidam) Orr & Plunkett, and M. striatosporum (Barron & Booth) Sigler produce distinctive chains of small (< 6 µm long), unicellular arthroconidia through the basipetal fragmentation of hyaline fertile hyphae. The fertile hyphae arise from the apices of solitary, erect, smooth to asperulate, melanized conidiophores that are normally 5–500 µm long, though some species diverge signiﬁcantly from this pattern. Oidiodendron myxotrichoides Calduch, Gené & Guarro produces fertile hyphae from the melanized branches of a reticulate conidioma. Oidiodendron hughesii Udagawa & Uchiyama, O. muniellense Calduch, Stchigel, Gené & Guarro, and O. setiferum Udagawa & Toyazaki have branched, melanized appendages surrounding the conidial mass at the conidiophore apices. Oidiodendron cerealis (Thüm.) Barron and M. setosum have short, hyaline to lightly melanized conidiophores and O. chlamydosporicum Morrall has thick-walled, melanized chlamydospores. **Current address for Adrianne V. Rice; Northern Forestry Centre, Natural Resources Canada, 5320-122 St., Edmonton, AB T6H 3S5 Canada The anamorph of M. arcticum also produces whorls of conidia that occur singly and in truncated chains along the conidiophore apex. Conidia are hyaline to dark and are lens-shaped, globose, subglobose, ellipsoidal, cylindrical, barrelshaped, pyriform, or irregular. Surface texture is asperulate, verruculose, dimpled, rugose, spinulose, or reticulate. Scanning electron microscopy (SEM) shows that the characteristic surface ornamentation is due to the presence of a persistent perispore membrane derived from the wall of the conidiogenous hypha. Wall material from the conidiogenous hypha also persists between adjacent conidia where it eventually collapses to form “connectives”. Species of Oidiodendron have been isolated worldwide, mostly from soil and decaying plant materials (Peyronel 1914, Smith 1946, Malan 1949, Barron 1962, Morrall 1968, Kobayasi 1969, Ellis 1971, Udagawa & Toyazaki 1987, Hambleton et al. 1998, Sigler & Flis 1998, Hambleton et al. 1998, Calduch et al. 2004, Roose-Amsaleg et al. 2004). Despite the widespread occurrence of this genus, there is no comprehensive key to the species. The keys in Barron (1962), Ellis (1971, 1976), Domsch et al. (1980), and Calduch et al. (2004) are out of date and rely exclusively on morphological characters. Calduch et al. (2004) include 23 species but four are not well accommodated in Oidiodendron, and three are 83 RICE & CURRAH synonyms of other species. The unnamed anamorphs of Myxotrichum species are not included in previous keys. Because morphological characters alone may be inadequate in hyphomycete species identiﬁcation, as is often revealed by molecular studies, we sought additional phenotypic characters by investigating a suite of simple physiological tests. These have been incorporated into updated dichotomous and synoptic keys to 24 species or varieties. Preceding the keys is a review of the taxonomic history, distribution and ecology of the genus. Following a description of the procedures used to describe morphological and physiological characters is an assessment of their taxonomic value. Species descriptions follow the keys and are in alphabetical order. Taxonomic History The hyphomycete genus Oidiodendron was established by Robak (1932) for three species isolated from wood pulp, O. fuscum Robak, O. nigrum Robak, and O. rhodogenum Robak. The genus has since grown to encompass 18 species named in Oidiodendron and the unnamed anamorphs of ﬁve species of Myxotrichum Kunze. Four species were added to the genus over the next 30 years. Newly described species included O. griseum Robak from wood pulp (Melin & Nannfeldt 1934) and O. ﬂavum von Szilvinyi from soil (von Szilvinyi 1941). Species transferred into the genus included Dicyma ambigua Peyronel, the putative anamorph of Myxotrichum aeruginosum Mont. (Peyronel 1914, Malan 1949), as O. ambiguum (Peyronel) Malan (Malan 1949) and Periconia tenuissima (Peck) as O. tenuissimum (Peck) Hughes (Hughes 1958). In 1962, Barron reviewed the genus, adding four new species, transferring a ﬁfth, and designating two pairs of synonyms. The new species Oidiodendron citrinum Barron, O. echinulatum Barron, O. maius Barron, and O. truncatum Barron were all isolated from peat soils in Ontario. Trichosporium cerealis Thüm. was transferred into Oidiodendron as an earlier synonym of O. nigrum Robak. Barron also considered O. fuscum synonymous with O. tenuissimum and designated it as the type of the genus. The ﬁrst key to the genus appeared in this publication and included nine species, O. cerealis, O. citrinum, O. echinulatum, O. ﬂavum, O. griseum, O. maius, O. rhodogenum, O. tenuissimum, and O. truncatum (Barron 1962). Hambleton et al. (1998), using ribosomal DNA sequences, determined that O. tenuissimum sensu Barron comprised two species. Our morphological and physiological evidence indicate that these correspond with O. fuscum Robak and O. tenuissimum (Peck) Hughes. We therefore recommend reinstatement of the original type. 84 Between 1962 and 1968, three additional species were described. The ﬁrst of these was O. gracile Zhdanova from the rhizosphere of maize (Zhdanova 1963). Morrall (1968) declared O. gracile a nomen dubium because no type was designated and because the original description and ﬁgures failed to clarify whether the conidia were arthroconidial or were produced by acrogenous budding. Morrall (1968) also described O. chlamydosporicum and O. periconioides Morrall from boreal forest soils. In 1968, Tewari and MacPherson (1968) discovered a fungus appearing to cause neuropathology in mice in vitro. They later described this species as Oidiodendron kalrae Tewari & MacPherson (Tewari & MacPherson 1971) [as “kalrai”]. This species was ultimately transferred to Arthrographis as Arthrographis kalrae (Tewari & MacPherson) Sigler & Carmichael [as “kalrai”] on the basis of its hyaline conidiophores and smooth conidia, which lack connectives (Sigler & Carmichael 1976). Two new species were described in 1969, Oidiodendron pilicola Kobayasi, based on an isolate colonizing human hair in contact with soil (Kobayasi 1969), and O. terrestre Roy & Singh from Indian soil (Roy & Singh 1969). We exclude O. terrestre from Oidiodendron because of its rapid growth, large, two-celled conidia, and hyaline conidiophores, and because the mode of its conidiogenesis is unclear in the original descriptions and illustrations. Stalpers (1974) transferred Oedocephalum sulphureum Cooke & Massee into Oidiodendron as O. sulphureum (Cooke & Massee) Stalpers but was concerned that the species might be a synonym of O. ﬂavum. We have not examined the type, no cultures are available, and Stalpers’ brief descriptions and illustrations leave room for doubt. Further details are found under “notes” following the description of O. ﬂavum. Tokumasu (1973) and Söderström and Bååth (1978) isolated a species similar to O. chlamydosporicum from soil in Japan and Europe; it appeared as O. scytaloides in the key by Domsch et al. (1980) although it was not validly published as O. scytaloides Gams & Söderström until three years later (Gams & Söderström 1983). Molecular evidence (Hambleton et al. 1998, Calduch et al. 2004) and our examination of ex-type cultures of O. scytaloides and O. chlamydosporicum suggest that they are synonyms. Cultures of “O. sindenia Beyer” were deposited in the American Type Culture Collection (1976) but the name was never validly published (Beyer, pers. comm., 2002). Two more species were described during the 1980s. The ﬁrst, O. robustum Mercado Sierra & Castañeda Ruiz, from bark of Bauhinia cumanensis Kunth in Cuba (Mercado Sierra & Castañeda Ruiz 1985), is excluded based on its inordinately large conidia and conidiophores and because the mode of OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM its conidiogenesis is unclear in the description and illustrations. Oidiodendron setiferum was described with branched, melanized appendages at the conidiophore apex, and the generic description was emended to accommodate this character (Udagawa & Toyazaki 1987). From this point on, a succession of new species bearing such spiny or myxotrichoid appendages was described. A second species with melanized appendages that were more elaborate than those of O. setiferum and that formed a “reticuloperidium-like” structure surrounding the arthroconidia was named O. hughesii in 1998 (Udagawa & Uchiyama 1998). Calduch et al. (2002) described O. myxotrichoides, which produces arthroconidia on the melanized hyphae of a reticulate conidioma that superﬁcially resembles the “reticuloperidium” of Myxotrichum ascomata. Calduch et al. (2004) described three more species with melanized appendages: O. muniellense Calduch, Stchigel, Gené & Guarro with setiform appendages and subglobose, roughened conidia, O. ramosum Calduch, Stchigel, Gené & Guarro with recurved appendages and smooth to slightly roughened conidia, and O. reticulatum Calduch, Stchigel, Gené & Guarro with ellipsoidal, roughened conidia and appendages resembling those of O. hughesii. Comparisons of the original descriptions and illustrations of O. hughesii, O. muniellense, O. ramosum, O. reticulatum, and ex-type material of O. setiferum suggest that O. reticulatum is a synonym of O. hughesii and O. ramosum is a synonym of O. setiferum. Finally, Rice and Currah (2005–this volume) describe O. ﬁmicola Rice & Currah from mushroom compost. The description is based on two cultures obtained from the Pennsylvania State University Mushroom Spawn Laboratory. In addition to the binomials in Oidiodendron, listed above, one named species and ﬁve unnamed species constitute the anamorphic components of holomorphs named in Myxotrichum. Oidiodendron ambiguum (Peyronel 1914, Malan 1949) is listed as the anamorph of Myxotrichum aeruginosum and unnamed Oidiodendron anamorphs are connected with M. cancellatum (Orr & Kuehn 1964), M. setosum (Orr et al. 1963), M. striatosporum [≡ Byssoascus striatisporus (Barron & Booth) von Arx] (Barron & Booth 1966, Sigler & Carmichael 1976), M. arcticum (Udagawa et al. 1994), and M. emodense (Udagawa & Uchiyama 1999). A relationship between the species of Oidiodendron and teleomorphic taxa within the Myxotrichaceae is strongly supported by molecular evidence (Hambleton et al. 1998) in addition to these anamorph-teleomorph connections. Placement of the Myxotrichaceae among the inoperculate discomycetes (Leotiomycetes) is supported by molecular data (Sugiyama et al. 1999, Mori et al. 2000, Gibas et al. 2002) and by a study indicating that the type of ascocarp development occurring in Myxotrichum is discomycetous in nature (Tsuneda & Currah 2004). Distribution, occurrence, and ecology Species of Oidiodendron are known as saprobes and come from a variety of living and decomposing plant, animal, and fungal substrates, including peat, soil, humus, wood, lichens, marine sediments and holothurians, human skin (incidental contamination only) and decomposing human hair (e.g. Robak 1932, Smith 1946, Barron 1962, Morrall 1968, Kobayasi 1969, Domsch et al. 1980, Hambleton et al. 1998, Sigler & Flis 1998, Pivkin 2000, Lumley et al. 2001, Calduch et al. 2004). They have also been identiﬁed from human food supplies (Delamarre & Batt 1999, Krysińska-Traczyk et al. 2001) and indoor air and dust samples (Udagawa & Toyazaki 1987, Horak et al. 1996, Reiman & Uitti 2000). They occur throughout the temperate regions (e.g. Domsch et al. 1980, Hambleton et al. 1998, Sigler & Flis 1998) and there are scattered reports from tropical and subtropical locales (Ellis 1971, Hambleton et al. 1998, Sigler & Flis 1998, Calduch et al. 2004, Roose-Amsaleg et al. 2004). Oidiodendron maius var. maius appears to form ericoid mycorrhizas in nature with members of the Ericaceae (Couture et al. 1983, Douglas et al. 1989, Hambleton & Currah 1997, Johansson 2001, Lacourt et al. 2001) and other species can produce morphologically similar structures in vitro (Dalpé 1986, 1989, 1991, Currah et al. 1993). This relationship is facultative for the fungi because they also persist as free-living saprobes in the same habitat (Tsuneda et al. 2001, Piercey et al. 2002, Rice & Currah 2002, in press). Despite the reports of Oidiodendron species from a diverse array of substrates and environments, little is known about their ecological roles in nature. Most reports are incidental and indirect (e.g. Delamarre & Batt 1999, Pivkin 2000, Lumley et al. 2001, RooseAmsalag et al. 2004). Few researchers try to isolate Oidiodendron species speciﬁcally, and few speculate on their ecological roles (Rice & Currah 2002). The exception is O. maius var. maius, which is conceived as having a mutualistic relationship with ericaceous roots and can predictably be isolated from them (Rice & Currah, in press). Most recent research on Oidiodendron has focused on the mycorrhizal status of various species and on the ecological signiﬁcance of this association (e.g. Couture et al. 1983, Dalpé 1986, 1989, Douglas et al. 1989, Dalpé 1991, Currah et al. 1993, Perotto et al. 1995, Bending & Read 1997, Hambleton & Currah 1997, Currah et al. 1999, Xiao & Berch 1999, Piercey et al. 2002, Usuki et al. 2003). 85 RICE & CURRAH While beneﬁts to the host plants have been observed in resynthesis studies, potential beneﬁts to the mycobiont (O. maius var. maius) have not been investigated. Ecological assessments have been hampered by the inability to identify species accurately (Hambleton & Currah 1997, Hambleton et al. 1998, Lacourt et al. 2001). Misidentiﬁcation of ericoid mycorrhizal isolates has led to difﬁculty in interpreting the speciﬁcity of these associations (Hambleton & Currah 1997, Hambleton et al. 1998, Lacourt et al. 2001, Rice & Currah, in press). Targeted isolation studies are required to determine which habitats and substrates are occupied by Oidiodendron species. These studies must be based on precise identiﬁcations so that estimations of the range, abundance, and distribution of Oidiodendron species in nature can be determined. Functional assessments, including enzyme assays and physiological proﬁles, mycorrhizal resynthesis and decomposition studies, and tests for pathogenicity are required to elucidate the niches occupied by these fungi. Data from functional assessments and from distributional studies should be compiled to provide a more accurate ecological picture. In vitro studies on the physiology of Oidiodendron species can provide insight into the potential roles these species play, although such studies do not provide information about actual ecological niches. Enzymatic studies on Oidiodendron have so far concentrated on the ecological implications of the cellulolytic abilities that have been detected (Dalpé 1991). All but two of the Oidiodendron species tested degraded cellulose azure, and various species produced other enzymes, including pectinases, lipases, gelatinases, and polyphenol oxidases, that potentially allow them to degrade a variety of plant, fungal, and animal-based substrates, including those found in soils. Broader substrate utilization proﬁles, including those generated by BIOLOG analyses (Rice & Currah 2005–this volume) could provide more information about the nutrition and potential ecological roles of Oidiodendron spp. Three Oidiodendron and two related Myxotrichum species (M. cancellatum, M. setosum, O. hughesii, O. myxotrichoides, and O. truncatum) are psychrophilic, with temperature optima below 20 °C. The remaining species are psychrotolerant, with temperature optima of 20–25 °C but with the ability to grow at temperatures as low as 5 °C. These species show decreased growth at temperatures over 25 °C. Such observations may explain the prevalence Oidiodendron species in temperate climates, where average summer temperatures are below 25 °C, and the scarcity of these species in warmer tropical and subtropical ecosystems. Most species of Oidiodendron are acidophilic with pH optima of 3–5. Their predilection for acidic growth 86 media may explain their abundance in peat (Barron 1962, Sigler & Flis 1998, Rice & Currah 2002, Rice, unpublished, Thormann et al. 2001, 2002, 2004) as well as in the acidic soils of coniferous forests (e.g. Morrall 1968, Gams & Söderström 1983). The reported growth of Oidiodendron species in marine Holothurians and associated sediments (Pivkin 2000) is unusual, but tolerance to relatively high salt concentrations does occur in some species (i.e. O. maius and O. truncatum see Rice & Currah 2001). The enzymatic abilities and acidophilic nature of ericoid mycorrhizal Oidiodendron species may partially explain the success of their host plants in acidic nutrient-poor soils (Rice & Currah 2001, in press). The failure of other Oidiodendron species to form either in vitro or in situ mycorrhizal associations may be explained by the relatively high pH optima and different enzymatic abilities of these species. For example, M. setosum has a high pH optimum and is unable to utilize either cellulose or tannic acid. These attributes may partly explain its apparent absence from in situ ericoid mycorrhizal associations even though it has been shown to form intracellular coils in these hosts in vitro (Dalpé 1989). The predilection shown by many Oidiodendron species for cold, acidic environments rich in plant, animal, and fungal debris may occur across the Myxotrichaceae. In addition to Myxotrichum and Oidiodendron, the family includes Gymnostellatospora Udagawa, Uchiyama & Kamiya, Pseudogymnoascus Raillo, and the widespread anamorphic Geomyces Traaen (Currah 1985, Sigler et al. 2000). Species of Geomyces produce small, dry, unicellular, barrelshaped to pyriform arthroconidia in dendritic clusters at the apices of erect, hyaline conidiophores (Sigler & Carmichael 1976). Species of Gymnostellatospora, Myxotrichum, and Pseudogymnoascus produce small, fusiform ascospores in deliquescent, globose asci within reticuloperidia (Currah 1985, Sigler et al. 2000). The physiological requirements of most Geomyces, Gymnostellatospora, and species of Pseudogymnoascus are poorly studied, but there are reports of cellulolytic activity (Dalpé 1991, Udagawa et al. 1993, Uchiyama et al. 1995, Sigler et al. 2000, Udagawa & Uchiyama 2000) and psychrophily (Uchiyama et al. 1995, Sigler et al. 2000, Udagawa & Uchiyama 2000). Reports of isolation of the teleomorphic taxa are rare, but most isolations have been from decaying plant material and soils in temperate and cool environments (Udagawa et al. 1993, Uchiyama et al. 1995, Sigler et al. 2000, Udagawa & Uchiyama 2000) where corresponding anamorphs may be common. Myxotrichum chartarum Kunze : Fr. lacks an anamorph but is also reported to be psychrophilic (Tribe & Weber 2002). Myxotrichaceous fungi are common on types of decaying plant material that are attractive to insects. OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM It has been suggested that the reticuloperidium of myxotrichaceous fungi is adapted for dispersal by arthropods (Currah 1985, Currah 1994, Greif & Currah 2003). Dispersal may be effected when the mesh-like peridial wall is impaled by the body hairs of insects or other arthropod carriers and plucked away from its substratum (Greif & Currah 2003). Wind dispersal of the small, dry conidia of Oidiodendron and Geomyces is likely, but these conidia may also be adapted for arthropod dispersal, adhering to carrier exoskeletons electrostatically (Greif & Currah 2003). Greif and Currah (2003) hypothesized that small arthropods may be important in dispersing the conidia locally while larger insects might disperse the ascocarps over longer distances to fresh substrates. It is possible that the reticulate conidiomata of O. myxotrichoides and the appendages of O. muniellense, O. setiferum and O. hughesii may function in a similar manner by attaching masses of conidia to arthropod vectors. MATERIALS AND METHODS Isolates were obtained from the University of Alberta Microfungus Collection and Herbarium (UAMH, Edmonton, Alberta, Canada), the Mushroom Spawn Laboratory, Pennsylvania State University (DC, University Park, PA, U.S.A.), and the Centraalbureau voor Schimmelcultures (CBS, Utrecht, the Netherlands). Information for some species was obtained solely from the literature. No ex-type or authentic cultures of O. ambiguum, O. hughesii, O. sulphureum, O. terrestre or M. emodense are available from culture collections. Oidiodendron muniellense, O. myxotrichoides, O. ramosum, and O. reticulatum were published too close to the completion of this manuscript to be studied directly. Isolates of O. pilicola and M. striatosporum from UAMH had degenerated to a point that made morphological study unreliable. A permanent slide of the anamorph of M. striatosporum was obtained from UAMH and used for microscopic measurements and description. Morphology Three replicates each of 40 isolates (16 species, Table 1) were grown as single-point-inoculated cultures on plates of cornmeal agar [CMA; 17 g Difco-Bacto corn meal agar (Difco Laboratories, Detroit, MI), 1 L dH2O] amended with 0.01 % oxytetracycline (Sigma Chemical Co., St. Louis, MO). Incubation was at room temperature in the dark. Colonies were measured and described at 28 d. Colony colour was determined without reference to a colour standard. Two separate slide cultures on 10 % (w/v) cereal agar (CER) (Sigler & Flis 1998) of each isolate were mounted after 14 d incubation at room temperature in the dark. Conidiophore colour, texture, and branching pattern were recorded, as were conidial shape, colour, and surface ornamentation. Conidiophores were described as “branched” when conidium-bearing branches arose from the pigmented apical region of the conidiophore. Whether branches were dichotomous or trichotomous was also noted. Conidiophore length was measured from the point of origin to the end of the melanized portion. Mean conidiophore lengths and conidial dimensions were calculated using at least 10 randomly selected conidiophores and conidia from each slide culture. Measurements are given as minimum-(mean)-maximum. Appendages (n = 10) of O. setiferum were measured from their origin on the conidiophore to the tip of the longest branch. The number of appendages per conidiophore was noted. Observations and measurements were made under oil immersion using an Olympus BX 50 light microscope (Olympus Optical Co., Tokyo, Japan). Photographs were made using an Olympus DP 12 Digital camera (Olympus Optical Co., Tokyo, Japan). SEM images of conidia were prepared using Mycelial plugs (5 mm × 5 mm) from ﬁve-wk-old cultures on CMA. These were freeze-dried in liquid nitrogen, and viewed on a cryo-stage in a JEOL #JSM6301FX7V SEM (JEOL U.S.A. Inc., Peabody, MA). Physiological Studies Thirty-eight isolates, representing 15 species, were used in the physiological tests (Table 1). Light, temperature and pH tolerance tests follow Rice and Currah (2001). Unless otherwise stated, enzymatic assays follow Hutchison (1990) and Rice and Currah (2001). The effects of three light, six temperature, and ﬁve pH treatments were studied using two replicates of each isolate grown on CMA. Growth rates (mm/d) were calculated using two independent measurements of colony radius of each replicate at 7, 14, 21, and 28 d, and were compared with designated ‘control’ growth conditions for each factor studied. Light treatments were diffuse natural daylight, 24 h darkness, and so-called “black light” regime combining ultraviolet light (Philips F20T12-BL, 20 W; Philips Lighting, New Jersey) and a ﬂuorescent “growlight” (Sylvania F20T12, 20W; Osram Sylvania, Mississauga, ON, Canada) (Hambleton & Currah 1997, Rice & Currah 2001). Temperature treatments were 5, 10, 15, 20, 25, and 30 ºC (± 1.5 ºC). To determine the effect of pH, isolates were grown on CMA adjusted to pH 3, 5, 7, 9, and 11 using 1 N hydrochloric acid (HCl) and 10 % potassium hydroxide (KOH). For enzyme assays, cultures were grown at room temperature in the dark on media containing the target macromolecule with or without an indicator. 87 Species Strain Source (original identiﬁcation where taxonomically signiﬁcant) CEL1 GEL2 LIP3 PEC4 STA5 TAM6 WDG7 Myxotrichum arcticum UAMH 7565T Forest soil, U.S.A. + + - + + + - M. arcticum M. cancellatum M. setosum UAMH 9243 UAMH 1996 UAMH 3835 UAMH 4535 Decayed spruce, Canada Soil, Japan Soil, Canada Washed mineral soil, Canada + - + + + + + + + + + + + + + + - - Oidiodendron cerealis O. cerealis UAMH 504 UAMH 1522 CBS 349.62 UAMH 6520T UAMH 6521T UAMH 6527 Human hair, Canada Peat soil, Canada Soil, Italy Soil, Canada Soil, Sweden (O. scytaloides) Soil, Sweden (O. scytaloides) + + + + + + + + + + + + + - + + + + + + + + + + + + - + + - UAMH 8510 Fir roots, Germany (O. scytaloides) + + + + + - - UAHM 9751 Sphagnum, Canada (O. scytaloides) + + + + + + - O. ﬂavum O. fuscum UAMH 8467A UAMH 10459T UAMH 10523 UAMH 1524A UAMH 8511T Peat soil, Canada Mushroom compost, U.S.A. Mushroom compost, U.S.A. Peat soil, Canada Wood pulp, Norway + NA NA + - + NA NA + + + NA NA + + NA NA + + + NA NA + + + NA NA - + NA NA - O. griseum UAMH 1403A Wood pulp, Norway + + - + + + - O. maius var. citrinum UAMH 4080 UAMH 8925 UAMH 1525 Wood chips, Canada Vaccinium roots, Canada Cedar bog soil, Canada + + + + + + + + + + + + + + + + + UAMH 7089 UAMH 9275 Ex sclerotia, stream drift, Canada Ex mycorrhizal root tip, Canada + + + + + + + + + + + + + + UAMH 1540T UAMH 8920 UAMH 9749 UAMH 10460 Peat soil, Canada Oxycoccus roots, Canada Decaying Sphagnum, Canada Vaccinium roots, Canada + + + + + + + + + + + + + + + + + + + + + + + + - UAMH 10461 Vaccinium roots, Finland + + + + + + - O. chlamydosporicum O. echinulatum O. ﬁmicola O. maius var. maius RICE & CURRAH 88 Table 1. Sources and enzymatic proﬁles for Oidiodendron isolates studied. Table 1. (Continued). Species O. periconioides O. rhodogenum O. setiferum O. tenuissimum 1CEL = cellulose azure. 2GEL = gelatin. 3LIP = TWEEN 6TAM 7WDG A LIP3 PEC4 STA5 TAM6 WDG7 + + - + + + - UAMH 7289 UAMH 8527T UAMH 1405A CBS 401.69 UAMH 5715T UAMH 1523 UAMH 8513 Humus, Japan (O. echinulatum) Soil, Canada Pulp sludge, Norway Soil, Canada House dust, Japan Forest soil, Canada Leaf litter, Spain + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + - - UAMH 1399T UAMH 8443 UAMH 10464 Forest soil, Canada Soil, Italy (O. ambiguum) Decaying spruce, Canada + + + + + + + + + + + + - - - 20 (lipid). = pectin. 5STA = T= GEL2 starch. = tannic acid medium. = wood guaiacol (lignin). ex-type. = authentic. + = positive reaction. – = negative reaction. NA = not tested. 89 OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM O. truncatum 4PEC CEL1 UAMH 6084 Source (original identiﬁcation where taxonomically signiﬁcant) Calypso roots, Canada Strain RICE & CURRAH Polyphenol oxidase (PPO) activity was assessed using tannic acid medium (TAM), consisting of 5 g tannic acid (BDH Inc., Toronto, ON, Canada) autoclaved in 200 mL dH2O then combined with a still-warm, previously autoclaved mixture of 15 g Difco malt extract, 20 g Difco agar, and 800 mL dH2O (Rice & Currah 2001) and wood guaiacol medium (WDG), consisting of 2 g powdered Picea glauca stem wood, collected locally, plus 18 g Difco agar and 1 L dH2O, all autoclaved together, with 100 µL guaiacol (Sigma Chemical Co., St. Louis, MO) then added to the autoclaved materials (Miyamoto et al. 2000). Mycelial plugs (5 mm × 5 mm) were placed on plates of TAM and incubated for 48 hr. Darkening of the medium under the plug was considered a positive reaction, indicating the ability to degrade soluble phenolic polymers (Bending & Read 1997). Isolates were point-inoculated on plates of WDG and incubated for 5 wk. Red discoloration of the medium around the mycelium indicated a positive reaction for the degradation of insoluble phenolic polymers, including lignin (Miyamoto et al. 2000). Cellulases were detected using cellulose azure (Smith 1977, Hutchison 1990, Rice & Currah 2001). Modiﬁed Melin-Norkrans agar (MMN) was made up as 12 g Difco agar, 3 g Difco malt extract, 1 g dglucose anhydrous (Sigma), 1 g CaCl2, 0.5 g NaCl, 10 g KH2PO4, 3 g MgSO4·7H2O, and 1 L dH2O. Twenty-ml volumes were added to 50 mL Pyrex tubes, autoclaved, and allowed to solidify. A 2 % (w/v) solution of washed cellulose azure (Sigma) in MMN was autoclaved and 2 mL was pipetted as a layer over the solidiﬁed plain MMN medium in each tube. Reactions were scored after 5 wk based on the release of azure dye from the upper layer into the basal MMN layer. Amylase activity was scored after isolates had grown for 3 wk on plates of MMN containing 2 g/L potato starch (BDH Inc., Poole, U.K.). Plates were ﬂooded with iodine solution (5 g KI, 1.5 g I, 100 mL dH2O) and decanted after several minutes to reveal a clear zone around the mycelium in strains positive for this enzyme. Pectinase activity was determined after incubation for 5 wk on MMN containing 5 g/L citrus pectin (Sigma). After plates were ﬂooded for 6 hr with a 1 % aqueous solution of hexadecylmethylammonium bromide (Sigma), a clear zone around the mycelium against an otherwise opaque background was interpreted as a positive indication of pectinase activity. Gelatinase activity was determined using MMN containing 60 g/L gelatin (Sigma) instead of agar. The gelatin was dissolved in 900 mL dH2O and autoclaved, the remaining ingredients were autoclaved in 100 mL dH2O. The solutions were combined before pouring. Inoculated plates were incubated for a maximum of 90 5 wk or until decomposition of the gelatin caused liquefaction of the medium. Lipase synthesis was determined using MMN containing 0.1 g/L CaCl2 and 10 mL/L TWEEN 20 [polyoxyethylene sorbitan monolaurate (Sigma)], added after autoclaving. Isolates were incubated for 16 wk and scored for the presence of macroscopically visible crystals of the calcium salt of the fatty acid beneath the mycelium. RESULTS AND DISCUSSION Evaluation of Key Characters Morphology: To date, keys to Oidiodendron species (Ellis 1971, 1976, Barron 1962, Domsch et al. 1980, Calduch et al. 2004) have been based exclusively on morphological characters, especially conidiophore length, conidial morphology, and cultural characteristics (Hambleton et al. 1998). Conidiophores typically are erect and melanized and they branch at the apices to produce chains of arthroconidia. Conidiophore length, used regularly to delimit species, ranges from less than 5 to 500 µm. However, this character varies signiﬁcantly among and even within conspeciﬁc isolates. For example, it ranged from 45 to 455 µm among 21 isolates of O. maius var. maius and from 123 to 455 µm within a single isolate (Rice & Currah 2001). Length ranges overlap among all species except O. cerealis (5–30 µm long) and M. setosum [typically < 5 µm long, though conidiophores up to 140 µm long have been observed (Sigler & Carmichael 1976)]. Consequently, the value of this character in identiﬁcation is limited. Nonetheless, because conidiophore length is a readily observable character and because ranges are given in all species descriptions, we have incorporated these measurements into the dichotomous key. Users should be aware that this character is most useful when tendencies toward very short or very long conidiophores are considered in conjunction with other features. Conidiophore branching, surface texture and pigmentation are useful in some instances. Some species have conidiophores that do not branch within the melanized portion, while in others, dichotomous, and occasionally trichotomous, branching occurs. The conidiophores of most species are either consistently smooth or faintly and inconsistently asperulate but those of O. ﬁmicola are scaly in SEM and asperulate in LM. Oidiodendron cerealis and M. setosum typically do not produce dark conidiophores; instead, conidiophores are short (typically < 5 µm long in our observations of M. setosum, up to 30 µm long in O. cerealis) and hyaline, resembling vegetative hyphae. In other species, inconspicuous conidiophores are always accompanied by larger, melanized conidiophores. OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM The structures commonly called “connectives” are the remains of the hyphal sleeve in which the conidia differentiate. This material persists as collapsed wall material between mature conidia. It is visible in many species, but its conspicuous presence is not consistent within or among isolates. This character is therefore not useful for distinguishing species. On the other hand, M. arcticum displays a unique form of conidiogenesis. Termed “geniculate conidiogenesis,” it produces truncate chains of one or two conidia borne in whorls at the conidiophore apex, and oriented perpendicular to the conidiophore axis (Udagawa et al. 1994, Tsuneda & Currah 2004). The ontogeny of these conidia is difﬁcult to discern using light microscopy, but the conidiophores involved terminate in a small, dense head of conidia, easily distinguished from the more diffuse conidial arrangements produced by conidiophores terminating in normal branched chains of arthroconidia. Conidial size varies little among species. It ranges from 1.5–3 × 1–2 µm to 3–7 × 2–4 µm, but most species produce conidia that are 1.5–5 × 1–2.5 µm. Colour, shape, and ornamentation are variable but are consistent within species, and therefore are useful characters. In light microscopy, conidia may appear hyaline, lightly pigmented, or dark. This trichotomy is important in our keys. Conidial colour en masse, as determined using the dissecting microscope, varies from white to pale grey to green-grey to brown to yellow. It largely accounts for the characteristic colours of colonies. Rice and Currah (2001) found that conidial ornamentation was consistent among 21 isolates of O. maius var. maius but distinct from that of a superﬁcially similar isolate of O. truncatum. This character provided a clearer distinction between these species than did conidiophore length and conidial size. Other species also have distinctive conidial surfaces. For example, the conidia of O. cerealis are lens-shaped with a thickened ring and have a rugose (wrinkled) perispore. Conidia of O. pilicola, O. truncatum, M. cancellatum, and M. striatosporum are all barrel-shaped with truncate ends but differ in surface ornamentation. In O. truncatum and M. cancellatum, conidia have a wrinkled, netlike perispore (resulting in characteristic “reticulate ornamentation”) while those of O. pilicola are smooth to minutely asperulate and those of M. striatosporum are asperulate. Oidiodendron ambiguum, O. echinulatum, and O. periconioides, all with subglobose to ellipsoidal conidia, differ in that the conidia of O. ambiguum have rounded and minutely verruculose (warty) surface projections, while those of O. echinulatum have larger, but still rounded, warty projections, and those of O. periconioides have pointed and spinulose projections. Oidiodendron muniellense and O. setiferum, which are morphologically similar to one another, can be distinguished by conidial ornamentation, which is asperulate to spinulose in O. muniellense and smooth to reticulate in O. setiferum. Conidia of other species may be only slightly asperulate, reticulate, warty, or dimpled in SEM and look smooth, or nearly so, by light microscopy. Oidiodendron ﬂavum and O. ﬁmicola produce a variety of conidial shapes with smooth to asperulate ornamentation, and can be seen to differ signiﬁcantly in this feature only in SEM. Conidial shapes are illustrated in Table 2. Unique features, when they occur, may be useful characters. Examples include the chlamydospores seen in O. chlamydosporicum, and the melanized appendages that arise at the conidiophore apices of O. muniellense, O. setiferum and O. hughesii, and that make up the peridium-like enclosure of the conidiomata of O. myxotrichoides. The appendages of O. hughesii are larger and more highly branched and complex than those of O. muniellense and O. setiferum, but are similar to those of O. myxotrichoides in forming a peridium-like structure surrounding the arthroconidia. In O. hughesii, peridium-like branches are borne on the conidiophore apex and do not form a sessile, ascocarplike conidioma. Colonial morphology, especially colour and the production of diffusible pigments and exudates, has also been used as a source of characters. It has the disadvantages, however, that it can vary according to the growth medium used and that it is not constant within isolates of the same species. Cultural characteristics are used in the keys only when they were reasonably consistent. Sigler & Gibas (2005–this volume) report a culture-based method for distinguishing O. maius from other species. Physiology: Physiological tests, including enzyme proﬁling and tests for tolerance of different growth conditions, have seldom been used to distinguish Oidiodendron species (Rice & Currah 2001). Some such characters do, however, appear to have discriminating value and are used in our dichotomous key where appropriate, as well as in the species descriptions and synoptic key. These characters are presented with the caveat that only a small number of isolates (1–5 per species) were tested to obtain proﬁles. The range of variation within species and across the genus may be underestimated. Neither light nor temperature preferences discriminated among most species but some minor distinctions are noted. For example, the growth of O. echinulatum was suppressed by daylight. Oidiodendron setiferum grew optimally at 25 ºC and O. truncatum, M. cancellatum, and M. setosum grew optimally below 20 ºC, with suppressed growth at 25 ºC. All others grew optimally at 20 ºC. Oidiodendron hughesii and O. myxotrichoides were not tested here but were described as psychrophilic, with optimal growth at 15 °C (Udagawa & Uchiyama 1998, Calduch et al. 91 RICE & CURRAH 2002) and O. muniellense grows optimally at 25 °C (Calduch et al. 2004). Species fell into two groups with respect to pH optima. Oidiodendron cerealis, O. chlamydosporicum, O. ﬂavum, O. fuscum, O. griseum, O. maius, O. periconioides, O. rhodogenum, O. setiferum, O. tenuissimum, M. cancellatum, and M. arcticum were acidophilic (pH optima < 5) while O. echinulatum, O. truncatum, and M. setosum grew optimally at higher pH (> 7). Substrate degradation tests can distinguish among morphologically similar species (Table 1). Oidiodendron fuscum, M. cancellatum, and M. setosum were unable to degrade cellulose azure, but the other tested species could all do this. Oidiodendron cerealis, O. periconioides, O. rhodogenum, O. setiferum, M. arcticum, and M. cancellatum were unable to degrade TWEEN 20, while this ability varied within O. chlamydosporicum. Only O. echinulatum was unable to degrade pectin, while the character was variable within O. periconioides. Oidiodendron cerealis, O. ﬂavum, O. fuscum, O. rhodogenum, O. tenuissimum, O. truncatum, M. cancellatum, and M. setosum were unable to degrade tannic acid, but O. chlamydosporicum and M. arcticum varied in this ability. Only O. maius var. citrinum and O. echinulatum consistently degraded lignin, while isolates of O. chlamydosporicum varied in their ability to degrade this substrate. All species liqueﬁed gelatin, and all but O. truncatum degraded potato starch. Keys to Oidiodendron The numbers given in parentheses after the species name in the keys below refers to the place of the taxon in the list of descriptions. Synoptic Key to Oidiodendron Character Character State Species Conidiomata Present O. myxotrichoides (18) Melanized appendages Absent Simple, antler-like All others O. muniellense (17) O. setiferum (22) Peridium-like Absent Present Absent Present Absent Darkly pigmented O. hughesii (14) All others O. chlamydosporicum (8) All others M. arcticum (1) All others M. striatosporum (5) O. cerealis (7) O. echinulatum (9) O. ﬂavum (11) O. muniellense (17) O. myxotrichoides (18) O. periconioides (19) O. tenuissimum (23) O. truncatum (24) M. arcticum (1) M. cancellatum (2) M. emodense (3) M. setosum (4) O. ambiguum (6) O. chlamydosporicum (8) O. fuscum (12) O. griseum (13) O. maius (15, 16) O. pilicola (20) O. ﬁmicola (10) O. hughesii (15) O. rhodogenum (21) O. setiferum (22) Chlamydospores “Geniculate conidiogenesis” Conidial colour Hyaline Lightly pigmented 92 OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Character Conidial ornamentation Character State Thickened ring Reticulate Species O. cerealis (7) M. cancellatum (2) O. truncatum (24) Warty or spiny O. ambiguum (6) O. echinulatum (9) O. periconioides (19) M. striatosporum (5) O. ﬁmicola (10) O. ﬂavum (11) O. hughesii (14) O. muniellense (17) O. tenuissimum (23) M. arcticum (1) M. emodense (3) M. setosum (4) O. chlamydosporicum (8) O. fuscum (12) O. griseum (13) O. maius (15, 16) O. myxotrichoides (18) O. pilicola (20) O. rhodogenum (21) O. setiferum (22) O. cerealis (7) O. ambiguum (6) O. echinulatum (9) O. fuscum (12) O. hughesii (14) O. muniellense (17) O. myxotrichoides (18) O. periconioides (19) M. cancellatum (2) M. striatosporum (5) O. pilicola (20) O. truncatum (24) M. arcticum (1) M. emodense (3) M. setosum (4) O. chlamydosporicum (8) O. griseum (13) O. maius (15, 16) O. rhodogenum (21) O. setiferum (22) O. tenuissimum (23) O. ﬁmicola (10) O. ﬂavum (11) M. arcticum (1) M. cancellatum (2) M. emodense (3) M. striatosporum (5) O. ambiguum (6) O. echinulatum (9) O. hughesii (14) O. muniellense (17) O. periconioides (19) O. pilicola (20) O. rhodogenum (21) Asperulate Indistinct Conidial shape Lens-shaped Globose-ellipsoidal Barrel-shaped (truncate) Subglobose, ellipsoidal or elongate Variable Conidiophore branching Branched 93 RICE & CURRAH Character Character State Melanized Species O. setiferum (22) O. truncatum (24) O. ﬂavum (11) O. fuscum (12) O. griseum (13) O. maius (15, 16) O. tenuissimum (23) M. setosum (4) O. cerealis (7) O. chlamydosporicum (8) O. ﬁmicola (10) M. setosum (4) O. cerealis (7) O. chlamydosporicum (8) O. ﬁmicola (10) All others Conidiophore texture Highly asperulate O. ﬁmicola (10) Colony surface colour Smooth or minutely asperulate Yellow All others M. setosum (4) O. maius var. citrinum (15) M. arcticum (1) M. cancellatum (2) M. emodense (3) O. ambiguum (6) O. ﬁmicola (10) O. fuscum (12) O. griseum (13) O. maius var. maius (16) O. rhodogenum (21) O. echinulatum (9) O. ﬂavum (11) M. striatosporum (5) O. cerealis (7) O. hughesii (14) O. muniellense (17) O. myxotrichoides (18) O. periconioides (19) O. setiferum (22) O. tenuissimum (23) O. truncatum (24) O. chlamydosporicum (8) M. cancellatum (2) M. setosum (4) O. hughesii (14) O. myxotrichoides (18) O. truncatum (24) O. chlamydosporicum (8) O. muniellense (17) O. setiferum (22) Unbranched Variable Conidiophore pigmentation Hyaline Variable Off-white or grey Pale brown Dark brown/green Optimal temperature Variable < 20 ºC > 20 ºC Optimal pH 20 ºC Basic (9–11) Acidic (3–5) 94 All others M. setosum (4) O. echinulatum (9) O. truncatum (24) All others OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Character Cellulose degradation Character State No Lignin (wood guaiacol) degradation Yes Yes Variable Lipid (TWEEN 20) degradation No Yes No Pectin degradation Starch degradation Tannic acid degradation Variable No Variable Yes No Yes Yes No Variable Species M. cancellatum (2) M. setosum (4) O. fuscum (12) All others O. echinulatum (9) O. maius var. citrinum (15) O. chlamydosporicum (8) All others M. setosum (4) O. echinulatum (9) O. ﬂavum (11) O. fuscum (12) O. maius (15, 16) O. tenuissimum (23) O. truncatum (24) M. arcticum (1) M. cancellatum (2) O. cerealis (7) O. griseum (13) O. periconioides (19) O. rhodogenum (21) O. setiferum (22) O. chlamydosporicum (8) O. echinulatum (9) O. periconioides (19) All others O. truncatum (24) All others O. echinulatum (9) O. griseum (13) O. maius (15, 16) O. periconioides (19) O. setiferum (22) M. cancellatum (2) M. setosum (4) O. cerealis (7) O. ﬂavum (11) O. fuscum (12) O. rhodogenum (21) O. tenuissimum (23) O. truncatum (24) M. arcticum (1) O. chlamydosporicum (8) 95 RICE & CURRAH Dichotomous Key to Oidiodendron 1a Conidia produced on fertile hyphae arising laterally or terminally from the melanized branches of a reticuloperidium like conidioma ....................................................................................... O. myxotrichoides (18) 1b Conidia produced on solitary conidiophores; conidiomata absent ....................................................................... 2 2a (1b) Conidiophores hyaline, in some isolates typically < 5 µm long and in others typically < 30 µm long (exceptional structures may be up to 130 µm long) .............................................................................................. 3 2b (1b) Conidiophores melanized, typically > 5 µm long ......................................................................................... 4 3a (2a) Colonies cream to yellow. Conidia hyaline, subglobose to elongate ...................................... M. setosum (4) 3b (2a) Colonies dark brown to black. Conidia melanized, subglobose to lens-shaped with a thickened ring ................................................................................................................................................... O. cerealis (7) 4a (2b) Conidiophores bearing melanized appendages at their apices ...................................................................... 5 4b (2b) Conidiophores not bearing melanized appendages at their apices ................................................................ 7 5a (4a) Appendages highly branched and anastomosing to form a reticulate network, 60–300 µm diam. including peripheral spines. Conidia pale olive brown, produced en masse at the centre of the reticulum .......................................................................................................................................................O. hughesii (14) 5b (4a) Appendages sparsely branched to form 2–6 setiform hairs. Conidia pale brown, produced from fertile hyphae arising from the conidiophore apex or from appendage branch points or tips......................................... 6 6a (5b) Appendages straight, up to 60 µm long. Conidia globose to subglobose, asperulate to echinulate ................................................................................................................................ O. muniellense (17) 6b (5b) Appendages often recurved, up to 130 µm long. Conidia subglobose to elongate or irregular, with smooth to faintly reticulate ornamentation ...............................................................................................O. setiferum (22) 7a (4b) Fertile hyphae swelling to form chains of vesicles, which form thick-walled, melanized, spiny, globose to ellipsoidal conidia, 3–6 × 2–4 µm ........................................................................................O. periconioides (19) 7b (4b) Fertile hyphae not forming vesicles. Conidia various ................................................................................... 8 8a (7b) Melanized chlamydospores present, 3–6 × 2–4 µm, borne on repent hyphae and conidiophores. Conidiophores 5–70 µm long (mean < 20 µm). Conidia hyaline, 1.5–3 × 1–2 µm ...... O. chlamydosporicum (8) 8b (7b) Chlamydospores absent. Conidiophores typically longer than 20 µm. Conidia hyaline or melanized ........ 9 9a (8b) Conidiophores asperulate under light microscopy. Conidia hyaline to pale brown, elongate to barrelshaped or irregular, 3–6 × 2–3 µm .................................................................................................O. ﬁmicola (10) 9b (8b) Conidiophores smooth under light microscopy. Conidia hyaline or melanized, subglobose to ellipsoidal, elongate, barrel-shaped or irregular .................................................................................................................... 10 10a (9b) Conidia subglobose to barrel-shaped with truncate ends ......................................................................... 11 10b (9b) Conidia globose, ellipsoidal, subglobose, elongate or irregular but neither barrel-shaped nor truncate .............................................................................................................................................................. 14 11a (10a) Conidia melanized, produced either on conidiophores < 200 µm long or directly from vegetative hyphae ................................................................................................................................................................ 12 11b (10a) Conidia hyaline, produced on conidiophores < 150 µm long ................................................................ 13 12a (11a) Mature colonies olive-green with yellow margins. Conidia 2–7 × 1.5–2.5 µm, smooth to asperulate with distinct apical scars, produced on unbranched or dichotomously branched conidiophores <100 µm long or directly from vegetative hyphae.........................................................................................................M. striatosporum (5) 12b (11a) Mature colonies brown to green-grey, yellow margin absent. Conidia 2–5 × 1–3.5 µm, with distinct apical scars and reticulate ornamentation, produced on dichotomously branched conidiophores 20–200 µm long .......................................................................................................................................... O. truncatum (24) 13a (11b) Conidiophores dichotomously or trichotomously branched, 25–100 µm long. Conidia 1.5–3.5 × 1–2.5 96 OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM µm, thick-walled, with reticulate ornamentation ................................................................... M. cancellatum (2) 13b (11b) Conidiophores dichotomously branched, 100–150 µm long. Conidia 3–3.5 × 1.5–2 µm, thin-walled, smooth.......................................................................................................................................... O. pilicola (20) 14a (10b) Conidia melanized ................................................................................................................................... 15 14b (10b) Conidia hyaline ....................................................................................................................................... 17 15a (14a) Conidia globose to broadly ellipsoidal, warty. pH optimum > 7. Conidiophores dichotomously branched ..................................................................................................................................O. echinulatum (9) 15b (14a) Conidia subglobose to elongate or irregular, with indistinct or asperulate ornamentation. pH optimum < 7. Conidiophores unbranched ........................................................................................................................ 16 16a (15b) Colonies cream. Conidia subglobose, ellipsoidal, pyriform, or irregular, thick walled, smooth to asperulate. Conidiophores 25–80 µm long .................................................................................... O. ﬂavum (11) 16b (15b) Colonies brown. Conidia subglobose to elongate, with indistinct to asperulate ornamentation. Conidiophores 30–250 µm long .......................................................................................... O. tenuissimum (23) 17a (14b) Colonies white to pale grey. Conidia produced in branching chains from fertile hyphae or in truncated chains (1-2 conidia) in whorls at the conidiophore apices. Conidia subglobose to elongate and irregular, 1.5–3.5 ×1–2.5 µm. Conidiophores dichotomously branched .................................................................. M. arcticum (1) 17b (14b) Colonies off-white, grey, or yellow. Conidia produced only in branching chains from fertile hyphae. Conidia globose to ellipsoidal or subglobose to elongate. Conidiophores unbranched or dichotomously branched ............................................................................................................................................................ 18 18a (17b) Colonies off-white to grey or green-grey. Conidiophores dichotomously branched. Conidia globose to ellipsoidal in some isolates and subglobose to elongate or irregular in others ................................................. 19 18b (17b) Colonies off-white to grey, or yellow. Conidiophores unbranched. Conidia subglobose, ellipsoidal or elongate ............................................................................................................................................................. 21 19a (18a) Colonies off-white to grey, sometimes with diffusible red pigment. Conidiophores 30–85 µm long. Fertile hyphae dichotomously branched. Conidia subglobose to elongate or irregular, 1.5–5 × 1.5–2 µm, with indistinct ornamentation ...................................................................................................... O. rhodogenum (21) 19b (18a) Colonies grey or green-grey, red pigment absent. Conidiophores up to 200 µm long. Fertile hyphae often verticillate. Conidia globose to ellipsoidal, verruculose and 3–4.5 × 2.5 µm in some isolates and subglobose to short cylindrical, smooth and 1.5–3.5 × 1.5–2 µm in others ........................................................................ 20 20a (19b) Colonies grey. Conidiophores 100–200 µm long. Conidia globose to ellipsoidal, 3–4.5 × 2.5 µm, verruculose .................................................................................................................................O. ambiguum (6) 20b (19b) Colonies grey or green-grey. Conidiophores 20–200 µm long. Conidia subglobose, ellipsoidal or short cylindrical, 1.5–3.5 × 1.5–2 µm, smooth ................................................................................... M. emodense (3) 21a (18b) Colonies off-white or yellow. Mean conidiophore length > 100 µm. Conidia produced in long undulating chains .............................................................................................................................................. 22 21b (18b) Colonies off-white to grey or grey-brown. Mean conidiophore length < 100 µm. Conidia produced in a dense head of non-undulating chains ................................................................................................................ 23 22a (21a) Colonies yellow to yellow-green. Conidia yellow en masse with a rugose perispore. Positive reaction in WDG test. Conidiophores 50–230 µm long ............................................................. O. maius var. citrinum (15) 22b (21a) Colonies off-white. Conidia white en masse with an asperulate perispore. Negative reaction in WDG test. Conidiophores 70–400 µm long ............................................................................ O. maius var. maius (16) 23a (21b) Colonies off-white to grey. Conidiophores 25–130 µm long. Conidia subglobose to cylindrical, 1.5–5 ×1–2 µm with an asperulate perispore. Degrades cellulose and tannic acid but not lipid...........O. griseum (13) 23b (21b) Colonies off-white to pale grey-brown. Conidiophores 15–40 µm long. Conidia subglobose to ellipsoidal, dimpled, 1.5–3 × 1–2 µm with an asperulate to verruculose perispore. Does not degrade cellulose or tannic acid, degrades lipid ............................................................................................................ O. fuscum (12) 97 RICE & CURRAH Table 2: Conidial shapes in Oidiodendron species. Conidial shape Illustration Species Subglobose to elongate, thin-walled, with idistinct ornnamentation Myxotrichum arcticum, M. emodense, M. setosum, Oidiodendron chlamydosporicum, O. fuscum, O. griseum, O. maius, O. setiferum, O. rhodogenum Barrel-shaped, truncate, with distinct dehiscence scars M. cancellatum, M. striatosporum, O. pilicola, O. truncatum Lens-shaped with a thickened ring O. cerealis Globose to elliptical, thick-walled, with echinulate ornamentation O. echinulatum, O. muniellense, O. periconioides Pyriform to irregular, thick-walled, with indistinct to asperulate ornamentation (not discernible at this scale) O. ﬁmicola, O. ﬂavum Subglobose to elongate, thickwalled, with indistinct to asperulate ornamentation (not discernible at this scale) O. ﬁmicola, O. ﬂavum, O. hughesii, O. myxotrichoides, O. tenuissimum 98 OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Species Descriptions 1. Oidiodendron anamorph of Myxotrichum arcticum Udagawa, Uchiyama & Kamiya, Mycotaxon 52: 198–204. 1994. Figs 1–3. Colonies on CMA 23–25 mm diam at 28 d, white to pale grey, appressed; reverse dark brown. Conidiophores abundant, bearing masses of white conidia, smooth, melanized, dichotomously branched at apex, 20–(75)– 215 × 2–4 µm. Conidiophores in some cases showing “geniculate conidiogenesis” and terminating in whorls of truncated chains of 1–2 conidia that are borne perpendicular to the conidiogenous cell, and in other cases terminating in hyaline, dichotomously branched fertile hyphae, 2–3 µm diam, that fragment to form chains of conidia. Conidia thin-walled, hyaline, subglobose to elongate and irregular, 1.5–(2.4)–3.5 ×1–(1.9)–2.5 µm, asperulate to spinulose under SEM. Maximal growth at 20 ºC and pH 3. Degrades cellulose, gelatin, pectin, and starch; UAMH 7565 also degrades tannic acid. Specimens examined: U.S.A., George Parks Hwy Road, Willow, north of Wasilla, Alaska, forest soil, Figs 1–3. Oidiodendron state of Myxotrichum arcticum. 1. Small dense head of subglobose to elongate, hyaline conidia at the apex of a tall, erect, melanized conidiophore [University of Alberta Microfungus Collection and Herbarium (UAMH) 7565]. Bar = 20 µm. Inset. “Geniculate conidiogenesis.” Conidiophore apex bearing whorls of truncated chains of one to two conidia. Arrow indicates connective between chain of two conidia, arrowheads indicate scars from detached conidia. Bar = 2.5 µm. Reproduced with permission from Tsuneda & Currah 2004, ﬁg 28. 2. Branches of fertile hyphae fragmenting to form subglobose to elongate, asperulate to spinulose conidia (UAMH 9243). Bar = 10 µm. 3. Chains of asperulate to spinulose, subglobose to elongate conidia with short connectives visible between them (UAMH 9243). Bar = 1 µm. 1992, Udagawa, (UAMH 7565, ex-type). Canada, Mariana Lake, Alberta, decaying Picea glauca, 1997, Lumley (UAMH 9243). Notes: The tall conidiophores and white conidia make this species superﬁcially similar to O. maius var. maius but the smaller conidia and the shorter and less undulate conidial chains of the M. arcticum anamorph are distinct. The peridial elements of the teleomorph are morphologically similar to those of sterile gymnothecia produced by O. maius var. maius (Rice & Currah 2002). Oidiodendron fuscum, O. griseum, and M. emodense have similar conidiophore lengths and also have dense conidiogenous heads. However, geniculate conidiogenesis is unique to M. arcticum. Molecular evidence suggests a close relationship between M. arcticum and O. griseum (Hambleton et al. 1998, Sigler & Gibas 2005–this volume). 2. Oidiodendron anamorph of Myxotrichum cancellatum Phillips, Grevillea 13:51–52. 1884. Figs 4–6. Colonies on CMA 11–13 mm diam at 28 d, white to grey, appressed at margins; reverse purple to black. Aerial hyphae and conidiophores abundant. Conidiophores bearing masses of off-white to grey conidia, melanized, smooth, branched dichotomously or trichotomously at apex, 25–(50)–100 × 2–4 µm. Conidia thick-walled, hyaline to lightly melanized at maturity, subglobose to barrel-shaped, 1.5–(2.6)–3.5 × 1–(1.7)–2.5 µm, reticulately ornamented with a rugose perispore and bearing conspicuous intercalary connectives. Maximal growth at 15–20 ºC and pH 5. Degrades gelatin, pectin, and starch. Figs 4–6. Oidiodendron state of Myxotrichum cancellatum (UAMH 1996). 4. Short, erect conidiophores bearing divergent chains of thick-walled, hyaline to lightly pigmented, barrel-shaped conidia. Bar = 15 µm. 5. Conidiophores bearing long chains of subglobose to barrel-shaped conidia. Bar = 10 µm. 6. Subglobose to barrel-shaped conidia with a rugose to reticulate perispore. Bar = 1 µm. 99 RICE & CURRAH Specimen examined: Japan, Tokyo, soil, 1959, Udagawa (UAMH 1996). Notes: Dalpé (1991) noted that this species uses the cellulose in Czapek cellulose agar but in the present study, the cellulose azure test was negative. Oidiodendron truncatum is similar but differs in having melanized conidia and dichotomously branched conidiophores. 3. Oidiodendron anamorph of Myxotrichum emodense Udagawa & Uchiyama, Mycoscience 40: 292–296. 1999. Figs 7–8. Colonies on oat agar (OA) 28–30 mm diam at 28 d at 25 °C, thin, with submerged vegetative mycelium, appearing granular due to the production of abundant ascomata intermixed with aerial hyphae and conidial heads; at ﬁrst greyish yellow, becoming greenish grey or olivaceous black, with clear exudates; reverse dull green or grey olivaceous; conidiogenesis moderate. Colonies on potato carrot agar (PCA) 21–22 mm diam at 28 d at 25 °C, ﬂoccose, plane, with thin vegetative mycelium, producing abundant conidia, greenish grey or smoke grey; exudate absent; reverse uncoloured to brownish grey or smoke grey. Conidiophores erect, arising from vegetative mycelium or aerial hyphae, straight below, branching at the top to produce an arborescent, olivaceous brown head; conidiophores olivaceous brown to dark brown, 25–200 µm long × 1.5–2.5 µm diam, straight, septate, thick-walled, smooth or sometimes with black nodes; branches hyaline to pale olivaceous brown, 10–60 × 2–2.5 µm, smooth-walled, repeatedly re-branched, frequently forming a verticillate whorl of 4–6 narrow fertile hyphae. Fertile hyphae hyaline, cylindrical, 1.2–1.5 µm diam, fragmenting to form conidial chains. Conidia hyaline, pale greyish green in mass, subglobose, ovoid, ellipsoidal or short cylindrical, 1.5–3.5 × 1.5–2 µm, almost smooth-walled, truncate at one or both ends. Connectives sometimes visible between conidia. Weakly cellulolytic. Reduced growth at 15 °C. Habitat: grassland soil, Nepal. Description is from Udagawa & Uchiyama (1999). Notes: This species is morphologically similar to O. fuscum, O. griseum, and M. arcticum but M. arcticum has geniculate conidiogenesis and O. griseum and O. fuscum have unbranched conidiophores and dichotomously branched fertile hyphae that are distinct from the verticillate whorls formed in M. emodense. 4. Oidiodendron anamorph of Myxotrichum setosum (Eidam) Orr & Plunkett, Can. J. Bot. 41: 1470–1471. 1963. Figs 9–11. Colonies on CMA 14–15 mm diam at 28 d, cream to pale yellow, appressed at margins; reverse cream to orange. Aerial conidia abundant, off-white to yellow en masse. Conidiophores typically less than 5 µm long or absent, hyaline to lightly melanized. Hyaline conidiophores 30–140 µm long were observed by Sigler & Carmichael (1976). Conidia hyaline, subglobose to elongate or irregular, 2–(3.6)–5 × 1.5– (2)–3 µm, produced in dichotomously branched chains at the conidiophore apices of reduced conidiophores or directly from vegetative hyphae. Maximal growth at 15 ºC and at alkaline pH. Degrades gelatin, pectin, lipid, and starch. Specimens examined: Canada, Mt. Allen, Kananaskis, Alberta, soil, 1971, Bissett (UAMH 3835); washed mineral soil particle, 1971, Bissett (UAMH 4535). Notes: The absence of melanized conidiophores is Figs 7–8. Oidiodendron state of Myxotrichum emodense. Reproduced with permission from Udagawa & Uchiyama 1999, ﬁgs 13–14. 7. Dichotomously branched conidiophore bearing verticillate whorls of fertile hyphae that give rise to subglobose to ellipsoidal and elongate conidia. Bar = 20 µm. 8. Divergent branches of a conidiophore give rise to verticils of fertile hyphae and thick-walled, subglobose to ellipsoidal conidia. Bar = 20 µm. 100 Figs 9–11. Oidiodendron state of Myxotrichum setosum (UAMH 3835). 9. Short, sparingly branched chains of elongate conidia produced from vegetative hyphae. Bar = 10 µm. 10. Chains of elongate conidia that collapse upon desiccation. Bar = 5 µm. 11. Short, unbranched chain of elongate conidia. Bar = 5 µm. OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM unusual in species of Oidiodendron. This character, along with the yellow colour of the colony, readily distinguishes the anamorph of M. setosum from other species. Molecular evidence supports a presumed relationship with other species of Oidiodendron (Hambleton et al. 1998). Oidiodendron sulphureum (Stalpers 1974), if it were to be re-collected and if it then turned out to be distinct from O. ﬂavum, would be similar to M. setosum, but it could be distinguished based on its darker yellow colonies, the presence of some melanized conidiophores, and curved fertile hyphae. More details about O. sulphureum are found under O. ﬂavum. 5. Oidiodendron anamorph of Myxotrichum striatosporum (Barron & Booth) Sigler, Mycotaxon 4: 385– 388. 1976. Figs 12–13. ≡ Arachniotus striatosporus Barron & Booth ﬁde von Arx ≡ Byssoascus striatisporus (Barron & Booth) von Arx (1971) ﬁde Sigler & Carmichael (1976) Colonies 15–20 mm diam at 14 d at 25 ºC on potato dextrose agar (PDA) and malt extract agar (MEA); 10 mm diam at 14 d and 25 ºC on Czapek’s synthetic agar. Colonies bright yellow at ﬁrst, becoming dark olivaceous in the center, smooth to slightly ﬂoccose, becoming funiculose; when mature olive-green with yellow margins, weakly zonate, with edges slightly irregular to scalloped. A thick turf of conidia is eventually produced, which may crack irregularly in older cultures. Colony description is from Barron & Booth (1966). Conidiophores present or absent; when present, melanized in the lower one-ﬁfth to one-third, [12–(35)–62.5 × 2–3 µm], unbranched or dichotomously branched, with upper portion Figs 12–13. Oidiodendron state of Myxotrichum striatosporum (UAMH 3758). 12. Conidiophores arising from a melanized section of the vegetative hyphae. The melanized lower portions of the conidiophores are unbranched and give rise to much longer, hyaline upper portions that branch several times and bear fertile hyphae. The fertile hyphae fragment to form dark, smooth to asperulate, thick-walled, barrel-shaped, truncate conidia with apical scars. Bar = 15 µm. 13. Long chains of dark, smooth to asperulate, thickwalled, barrel-shaped to rectangular conidia with darker apical scars. Bar = 15 µm. hyaline to subhyaline (up to 50 µm long), branching dichotomously and producing fertile hyphae, 1–1.5 µm diam, that fragment to form long, branched chains of conidia. Conidia barrel-shaped, smooth to asperulate, truncate with pigmented basal scars, hyaline to yellow when immature, yellow-brown to brown at maturity, 2–(4)–7 × 1.5–(2)–2.5 µm. Specimen examined: Canada, Bradford Marsh, Ontario, soil, 1960, Barron (UAMH 3758), ex-type Arachniotus striatosporus). Degenerate and no longer producing conidia. A permanent slide of the type was obtained from UAMH and used to obtain microscopic measurements. Notes: This species is known only from the type but it is easily distinguished from other Oidiodendron species based on its olive-green colonies with yellow margin and by its yellow to brown, truncate, asperulate conidia. 6. Oidiodendron ambiguum (Peyronel) Malan, Nuovo Giornale Botanico Italiano 56: 735–737. 1949. Fig 14. ≡ Dicyma ambigua Peyronel ﬁde Malan (1949) Fig. 14. Oidiodendron ambiguum. Reconstructed from the descriptions of Peyronel (1914) and Malan (1949). Tall conidiophore bearing branched fertile hyphae and verruculose, subglobose to ellipsoidal conidia. Bar = 20 µm. 101 RICE & CURRAH Colonies “large” (quote from the original description; dimensions not speciﬁed), round, initially ash grey, later darkening to an intermediate mouse grey. Vegetative hyphae septate, mostly hyaline and 1– 2.5 µm diam, some melanized and 3–7 µm diam. Conidiophores arising from areas of dark hyphal growth that are spaced at relatively regular intervals in the predominantly hyaline mycelium, erect, rigid, septate, melanized at maturity, 100–200 × 2–4 µm, with apices bearing dichotomous primary branches with many dichotomous, verticillate, or sympodial sub-branches. Conidia formed in branched chains along swollen terminal branches, hyaline, globose to ellipsoidal, minutely verruculose, 3–4.5 × 2.5 µm, grey en masse, giving the colony its characteristic colour. Source of isolation: air samples from an alpine forest. Description is from Peyronel (1914) and Malan (1949), translated from Italian. [UAMH 8443 (=ATCC 36256) from Italy, soil of snow valley, Mosca (received from ATCC as O. ambiguum) was reidentiﬁed as O. truncatum]. Notes: Peyronel (1914) was uncertain about the mode of conidial development and, as a consequence, his description and ﬁgures are unclear. Malan (1949) considered development to be arthroconidial, and placed this species within Oidiodendron. Improved illustrations were provided, but little was added to the written description. The illustrations provided by Malan (1949) coupled with isolation data, suggest that this is likely to be an Oidiodendron species. Neither Peyronel nor Malan, however, speciﬁed a type or deposited specimens. The only record of O. ambiguum since Malan is UAMH 8443, which was reidentiﬁed by us as O. truncatum on the basis of its dark, barrel-shaped conidia with reticulate ornamentation. If encountered again, O. ambiguum would be distinguished by its verruculose, hyaline, globose to ellipsoidal conidia. 7. Oidiodendron cerealis (Thüm.) Barron, Can. J. Bot. 40: 594–595. 1962. Figs 15–17. ≡ Trichosporium cerealis Thüm. ﬁde Barron (1962) ≡ Stephanosporium cereale (Thüm.) Swart ﬁde Swart (1965) = Oidiodendron nigrum Robak ﬁde Barron (1962) Colonies on CMA 30–34 mm diam at 28 d, greengrey (CBS 349.62) or pale with clumps of brown to black conidia (UAMH 504, UAMH 1522), reverse green-grey to black (CBS 349.62) or dark brown to black beneath areas of heavy sporulation (UAMH 504, UAMH 1522). Aerial hyphae abundant and hyaline in UAMH 504 and UAMH 1522 but scarce in CBS 349.62. Conidiophores short, branched, hyaline to lightly melanized, 5–(15)–28 × 2–3 µm. Conidia melanized, in short chains or appearing to be clumped at conidiophore apex, subglobose to lens-shaped with a 102 Figs 15–17. Oidiodendron cerealis. (UAMH 1522). 15. Dark, lens-shaped conidia produced in clusters at the apices of short, hyaline to lightly pigmented conidiophores. Bar = 10 µm. 16. Short conidiophores branched at the apices and supporting chains of lens-shaped conidia with an extremely rugose perispore. Bar = 1 µm. 17. Lens-shaped conidia with a rugose perispore. Bar = 1 µm. thickened ring and highly rugose (wrinkled) perispore, 2.5–(3.3)–4 × 2–(2.8)–4 µm. Maximal growth at pH 3–5 and 20 ºC. Degrades cellulose, gelatin, pectin, and starch. Specimens examined: Italy, Piedmont, alpine meadow soil, 1962, Dal Vesco (CBS 349.62); Canada, Edmonton, Alberta, human hair, 1956, Carmichael (UAMH 504); Bradford Marsh, Ontario, peat soil, 1960, Barron (UAMH 1522). Notes: This species is unique because of its hyaline conidiophores and lens-shaped arthroconidia with thickened rings of cell wall material. These features led to its placement outside of the genus Oidiodendron. Molecular analyses, however, support its placement within Oidiodendron (Hambleton et al. 1998). Its morphological distinction is signiﬁcant only at the species level. 8. Oidiodendron chlamydosporicum Morrall, Can. J. Bot. 46: 205–206. 1968. Figs 18–19. = Oidiodendron scytaloides Gams & Söderström (1983) Colonies on CMA 9–16 mm diam at 28 d, cream or pale grey to green-grey or brown, darker at margins, appressed; reverse cream near margin, becoming dark brown at centre. Conidia and chlamydospores pale to OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Figs 18–19. Oidiodendron chlamydosporicum. 18. Elongate, hyaline conidia produced in short chains at the apices of short, dark conidiophores and lateral, terminal, and intercalary dark, subglobose to elongate or irregular chlamydospores produced singly or in short chains from vegetative hyphae (UAMH 9751). Bar = 10 µm. 19. Asperulate, elongate conidia (C) in short chains at a conidiophore apex, intercalary, pitted chlamydospore (arrowhead) borne on a vegetative hypha (UAMH 6520). Bar = 1 µm. brown en masse, produced on repent hyphae at the surface of the agar or on well developed conidiophores that are mainly found near the centres of colonies. Conidiophores (2–3.5 µm diam) intergrading between structures that are short [3–(10)–17 µm long], branched, and lightly pigmented to melanized, and structures that are erect, melanized and 5–(35)–70 µm long; short and long types both bear chains of hyaline conidia interspersed with melanized chlamydospores. Conidia thin-walled, hyaline, globose, subglobose or elongate, 1.5–(2.5)–5 × 1–(1.7)–2.5 µm, produced in chains arising from vegetative hyphae or from conidiophores. Chlamydospores subglobose to barrelshaped or pyriform, thick-walled, melanized, 3–(4)–7 × 2–(3.5)–4µm, abundant, arising singly or in short chains from vegetative hyphae or conidiophores. In SEM, conidia minutely asperulate and chlamydospores pitted. Maximal growth at 20–25 ºC and pH 3. All isolates tested degrade cellulose, gelatin, pectin and starch; UAMH 6520, UAMH 8510, and UAMH 9751 degrade lipid; UAMH 6520 and UAMH 6521 degrade lignin; and UAMH 9751 degrades tannic acid. Specimens examined: Canada, Candle Lake, Saskatchewan, boreal forest soil, 1964, Morrall (UAMH 6520, ex-type); Perryvale, Alberta, Sphagnum fuscum (Schimp.) Klinggr., bog, Thormann (UAMH 9751, as O. scytaloides); Sweden, humus, Picea abies (L.) Karst. forest, 1973, Söderström & Bååth (UAMH 6521, ex-type of O. scytaloides); Kongalund, illuvial soil, Picea abies forest, 1973, Söderström & Bååth (UAMH 6527, as O. scytaloides); Germany, Freiberg, roots of dying Abies alba Miller, 1981, Schuler (UAMH 8510, as O. scytaloides). Notes: Oidiodendron chlamydosporicum was described as having subglobose to globose, terminal or intercalary chlamydospores, 4–9 µm diam, and subglobose, ellipsoidal or cylindrical conidia, 2–6 ×1.2–2 µm (Morrall 1968). Oidiodendron scytaloides was described as having smaller (3–5 × 2.5–3 µm) ellipsoidal chlamydospores formed in short, terminal, lateral, or intercalary chains and as having relatively short (2–4 × 1–2 µm) cylindrical or ellipsoidal conidia (Gams & Söderström 1983). The ex-type specimens of the two species, however, are indistinguishable in terms of chlamydospore shape and size: the shape ranges from subglobose to barrel-shaped or pyriform and the size is within the range 3–7 × 2–4 µm in each isolate. Moreover, conidial size, which overlapped in the original descriptions, is 1.5–5 × 1–2.5 µm in all isolates. Oidiodendron chlamydosporicum has priority over O. scytaloides, which is here relegated to synonymy. Molecular analyses support their conspeciﬁcity (Hambleton et al. 1998, Calduch et al. 2004). 9. Oidiodendron echinulatum Barron, Can. J. Bot. 40: 595–597. 1962. Figs 20–21. Colonies on CMA 35–37 mm diam at 28 d, offwhite to tan, ﬂoccose, with brown exudate; reverse dark brown. Aerial hyphae abundant, hyaline. Conidiophores abundant, bearing masses of brown conidia, dichotomously branched, melanized, smooth, 12–(35)–88 × 2–5 µm. Additional conidiogenous branches arising directly from vegetative mycelium, hyaline, 2–3 µm diam, dichotomously branched, fragmenting into chains of conidia. Conidia thickwalled, melanized, globose, subglobose or ellipsoidal, warted at maturity, 2–(3)–4 × 2–(2.6)–3 µm. Growth is suppressed by daylight. Maximal growth at pH 11 and 20 ºC. Degrades cellulose, gelatin, lipid, starch, tannic acid and lignin. Specimen examined: Canada, Ontario, peat soil, cedar bog, Barron (UAMH 8467, authentic). Notes: Oidiodendron echinulatum can be distinguished from other species in the genus by its branched conidiophores, warted conidia, growth suppression by Figs 20–21. Oidiodendron echinulatum (UAMH 8467). 20. Erect conidiophore bearing divergent, branched chains of thick-walled, warty, dark, subglobose to ellipsoidal conidia. Bar = 15 µm. 21. Subglobose to ellipsoidal, warty or pitted conidia. Short connectives are visible between some conidia. Bar = 1 µm. 103 RICE & CURRAH light, maximal growth at pH 11, and positive WDG reaction. Oidiodendron periconioides is similar but has spiny, globose conidia, is WDG negative, and is not inhibited by light. 10. Oidiodendron ﬁmicola Rice & Currah (2005–this volume), Figs 22–24. = Oidiodendron sindenia nomen invalidum ﬁde Rice & Currah (2005) Colonies on CMA 19–26 mm diam at 28 d, off-white to beige or pale grey, appressed with concentric rings of abundant conidiophores bearing masses of off-white to beige conidia; reverse olivaceous. Conidiophores present or absent, branched or unbranched, melanized, asperulate to scaly, 20–(50)–100 × 2–4 µm. Fertile hyphae hyaline, 2 µm diam, fragmenting to form short, dichotomously branched chains of arthroconidia. Conidia thick-walled, hyaline to light brown, barrelshaped to elongate or irregular, more or less truncate at one or both ends, asperulate, 3–(4.9)–6 × 2–(2.4)–3 µm. Specimens examined: U.S.A., St. Louis, Missouri, mushroom compost, 1976, Beyer (UAMH 10459 = DC 60, as Oidiodendron sp., ex-type); California, mushroom compost, 1976, Beyer (UAMH 10523 = DC 61, as Oidiodendron sp.). Notes: D. M. Beyer labelled material he sent for deposit in ATCC in 1976 “O. sindenia”, but never validly published the name. The material deposited at ATCC was listed in the catalogue under O. sindenia but it has since died (ATCC, pers. comm.). Beyer sent us cultures from the Pennsylvania State Mushroom Spawn Laboratory. One of these, DC 60 (= UAMH 10459), is reportedly from the same collection as the material deposited in ATCC. Oidiodendron ﬁmicola is the only Oidiodendron species that has consistently asperulate conidiophores, a character that distinguishes it from the morphologically similar O. ﬂavum. 11. Oidiodendron ﬂavum von Szilvinyi, Zbl. Bakt. Abt. II, 103: 179. 1941. Figs 25–27. Colonies on CMA 27–28 mm diam at 28 d, cream to yellow-brown, appressed; reverse dark brown. Hyphae submerged at colony margins. Conidiophores abundant, bearing masses of brown to grey conidia, smooth, unbranched, melanized, 25–(45)–80 × 2–4 µm. Fertile hyphae hyaline, 2–3 µm diam, 2–4 times dichotomously branched, fragmenting into short chains of 2–10 conidia. Conidia thin-walled, hyaline and elongate when immature, becoming globose to irregular, barrel-shaped, ellipsoidal or pyriform, thickwalled, melanized, smooth to asperulate or dimpled, 2.5–(3.3)–4 x 2–(2.8)–3µm at maturity. Maximal growth at pH 3 and 20 ºC. Degrades cellulose, gelatin, lipid, pectin, and starch. Specimen examined: Canada, Aberfoyle, Ontario, peat soil, cedar bog, Barron (UAMH 1524, authentic). Figs 22–24. Oidiodendron ﬁmicola (UAMH 10459). 22. Short, asperulate conidiophores bearing short chains of thick-walled, lightly pigmented to dark, barrel-shaped to elongate or irregular conidia. Bar = 15 µm. 23. Portion of fertile hypha bearing chains of asperulate, subglobose to elongate or barrel-shaped conidia with long, thin connectives visible between conidia. Bar = 5 µm. 24. Fragment of scaly conidiophore and asperulate, elongate to irregular conidia with the remnants of connectives remaining at their apices. Bar = 1 µm. 104 Notes: Oidiodendron ﬂavum is distinguished by the wide variation in the shape of mature melanized conidia and by the changes in the shape and pigmentation of conidia during maturation. Oidiodendron ﬁmicola is similar in displaying a range of conidial shapes and pigmentation, but O. ﬂavum is distinct in having smooth conidiophores and relatively round and smooth conidia. Molecular evidence suggests a close relationship between O. ﬂavum and O. griseum (Hambleton et al. 1998, Lacourt et al. 2001, Sigler & Gibas 2005–this volume). However, the consistency of the phenotypic differences between the authentic strains of the two species merits maintenance of the two names. Stalpers (1974) transferred Oedocephalum sulphureum to Oidiodendron as Oidiodendron sulphureum and suggested that it was similar or identical to O. ﬂavum because the conidial dimensions, given as 3.8–5 × 2.5–3.3 µm, are similar to those noted by von Szilvinyi (1941) (3.4–5.7 × 2.5–3.4 µm) and because the curved branches on the fertile hyphae of O. sulphureum were also mentioned by Barron (1962) in connection with O. ﬂavum. The brief description provided by Stalpers (1974) does OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Figs 25–27. Oidiodendron ﬂavum (UAMH 1524). 25. Erect conidiophores bearing short chains of thick-walled, dark, pyriform to irregular conidia. Bar = 15 µm. 26. Smooth to pitted, subglobose to pyriform conidia borne on fertile hyphae. Bar = 1 µm. 27. Smooth to pitted, subglobose to pyriform or irregular conidia. Bar = 1 µm. not provide measurements for conidiophore length, but instead describes the conidiophores as “rather short or absent, to 3.5 µm wide, with a pigmented, sometimes roughened basal part and a hyaline repeatedly branched upper part.” The conidiophore is not shown in his illustration. No cultures are available and we have not examined the type so we are unable to ascertain the precise placement of this species. Based on Stalpers’ brief description and illustrations, we are including it under O. ﬂavum. If encountered again, O. sulphureum would be distinguishable by virtue of its short conidiophores, sulphur-yellow colonies and curved fertile hyphae. 12. Oidiodendron fuscum Robak, Saertryk av Nyt Mag. Naturvidensk. 71: 249–251.1932. Figs 28–30. Colonies on CMA 24–26 mm diam at 28 d, offwhite to pale grey, appressed; reverse grey-brown to black. Conidiophores abundant, bearing masses of off-white to grey conidia, smooth, unbranched, melanized, 15–(25)–40 × 2–3 µm. Fertile hyphae 105 RICE & CURRAH Figs 28–30. Oidiodendron fuscum (UAMH 8511). 28. Tall, erect conidiophore bearing a dense head of thin-walled, subglobose to ellipsoidal conidia. Bar = 15 µm. 29. Conidiophore bearing a large, dense head of dimpled, asperulate, subglobose conidia. Bar = 10 µm. 30. Short chain of subglobose to ellipsoidal, dimpled, asperulate to minutely verruculose conidia. Long connectives are visible between conidia. Bar = 1 µm. hyaline, dichotomously branched, fragmenting to form chains of conidia in a dense head. Conidia thin-walled, hyaline to lightly pigmented, dimpled, subglobose to ellipsoidal with an asperulate to minutely verruculose perispore, 1.5–(2)–3 × 1–(1.5)–2 µm. Maximal growth at pH 3 and 20 °C. Degrades gelatin, lipid, pectin, and starch. Specimen examined: Norway, wood pulp, Robak (UAMH 8511, ex-type). Notes: Robak (1932) described O. fuscum as having 106 grey-brown to brown colonies, featuring smooth, branched or unbranched conidiophores 60–265 µm long, averaging 110–120 µm, as well as hyaline to greenish brown conidia 1.6–3.6 × 1.2–2.2 µm, averaging 2.4 × 1.7 µm. Barron (1962) made O. fuscum a synonym of O. tenuissimum and described O. tenuissimum as a variable species with off-white to grey or brown colonies and hyaline to pigmented conidia. Nuclear ribosomal sequence analyses indicated that O. tenuissimum sensu Barron comprises two distinct lineages. The ﬁrst, containing UAMH 8511, was OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM designated “O. tenuissimum” and the other lineage was called “O. sp. nov” (Hambleton et al. 1998). SEM examination of the conidia of UAMH 8511, UAMH 8513 (“O. sp. nov”), and the type specimen of Periconia tenuissima, showed that UAMH 8511 was distinct, while UAMH 8513 looked the same as the type of P. tenuissima. UAMH 8511 also differs in cultural morphology from the type of P. tenuissima (Hambleton, pers. comm.). We regard O. fuscum as a distinct species on the basis of these morphological and molecular differences. Oidiodendron fuscum is morphologically similar to the anamorphs of M. arcticum and M. emodense, as well as to O. griseum and O. maius var. maius. It lacks the geniculate conidiogenesis of M. arcticum and the verticillate fertile hyphae of M. emodense. On average, the conidia and conidiophores of O. fuscum are shorter than those of O. maius var. maius and O. griseum. Morphological differences between the conidia of O. fuscum and O. griseum are best observed using SEM. Oidiodendron fuscum produces subglobose to ellipsoidal, dimpled, minutely verruculose conidia while O. griseum has subglobose to cylindrical, asperulate conidia. 13. Oidiodendron griseum Robak, Saertryck ur Svensk. Skogvårdsföreningens. Tidskr. 3–4: 440. Figs 31–33. Colonies on CMA 26–32 mm diam at 28 d, off-white to pale grey, appressed; reverse dark green-grey to black. Conidiophores abundant, bearing masses of offwhite to grey conidia, smooth, unbranched, melanized, 25–(60)–130 × 2–5 µm. Fertile hyphae hyaline, 2–3 µm diam, dichotomously branched with acute branch angles, fragmenting to form long chains, of up to 30 conidia, in a dense fertile head. Conidia thin-walled, hyaline, subglobose to elongate or cylindrical, 1.5– (2.5)–5 × 1–(1.5)–2 µm, with an asperulate perispore. Maximal growth at pH 3 and 20 °C. Degrades cellulose, gelatin, pectin, starch, and tannic acid. Specimens examined: Sweden, wood pulp, 1960, Melin (UAMH 1403, authentic). Canada, Westlock, Alberta, wood chips and bark, ex logging truck, Sigler (UAMH 4080); Slave Lake, Alberta, roots of Vaccinium myrtilloides, Pinus banksiana stand, sand dune, Hambleton (UAMH 8925). Notes: Oidiodendron griseum is morphologically similar to the anamorphs of M. arcticum and M. emodense, as well as to O. maius var. maius, and O. fuscum. It lacks the geniculate conidiogenesis of M. arcticum and has unbranched conidiophores and dichotomously branched fertile hyphae as opposed to the branched conidiophores and verticillate fertile hyphae of M. emodense. Historically, there have been problems distinguishing isolates of O. griseum with longer-than-average conidiophores from isolates of O. maius var. maius (Hambleton & Currah 1997, Hambleton et al. 1998). However, the fertile hyphae of O. griseum have narrower branch angles and are less undulate than those of O. maius var. maius. The average conidiophore length in O. griseum, < 100 µm, is less than in O. maius var. maius, where the average is > 100 µm. Conidia of O. griseum are shorter on average (< 3 µm) than those of O. maius var. maius (> 3 µm). Molecular studies have indicated a complex relationship between O. griseum and the polyphyletic O. tenuissimum sensu Barron (Hambleton et al. 1998, Lacourt et al. 2001, Hambleton, unpubl. data). Hambleton et al. (1998) found that isolates of O. griseum and O. tenuissimum produced indistinguishable RFLP patterns but formed distinct clusters based on ITS sequence data. A similar study (Lacourt et al. 2001), based on a different set of isolates, found no ITS differences between the two species. Hambleton (unpublished) has found that a clade encompassing all sequenced isolates ever identiﬁed as O. griseum and O. tenuissimum sensu Barron is so broad that it encompasses isolates of all the other sequenced Oidiodendron species. However, with the division of O. tenuissimum sensu Barron into O. fuscum and O. tenuissimum sensu stricto, the similarities between O. griseum and O. tenuissimum are minimal. Oidiodendron griseum is morphologically and physiologically most similar to O. fuscum. According to Robak’s original descriptions of O. griseum (Melin & Nannfeldt 1934) and O. fuscum (Robak 1932), the two differ primarily in colony morphology and show only slight differences in conidiophore lengths and conidial dimensions. Robak described the colonies of O. griseum as green-grey with a dark green-black reverse (Melin & Nannfeldt 1934) and the colonies of O. fuscum as brown or grey-brown with a brownblack reverse (Robak 1932). We did not observe these cultural differences, possibly because different growth media were used. Both O. griseum and O. fuscum were similar in having off-white to grey colonies with a dark grey to black reverse. Furthermore, conidiophore lengths and conidial dimensions given for the two species overlap. In O. griseum, the conidiophores range in length from 40 to 150 µm, averaging 90–100 µm (Melin & Nannfeldt 1934), while those of O. fuscum range from 60 to 265 µm, averaging 110–120 µm (Robak 1932). Conidia of O. griseum are 2.0– 3.6 × 1.6–2.0 µm, averaging 2.6 × 1.8 µm (Melin & Nannfeldt 1934), while those of O. fuscum are 1.6–3.6 × 1.2–2.2 µm, averaging 2.4 × 1.7 µm (Robak 1932). The range in length of conidiophores we observed (25–130 µm) is smaller than that recorded by Robak although there is considerable overlap. These different 107 RICE & CURRAH Figs 31–33. Oidiodendron griseum. 31. Conidiophore bearing long chains of elongate to cylindrical conidia (UAMH 1403). Bar = 15 µm. 32. Chains of asperulate, subglobose to elongate or cylindrical conidia with short connectives visible between some of the conidia (UAMH 4080). Bar = 5 µm. 33. Asperulate, subglobose to elongate to cylindrical conidia with intervening connectives sometimes visible (UAMH 4080). Bar = 5 µm. ranges might be explained by our use of slide cultures and different media. Our measurements of mean conidiophore length (60 µm) were less than Robak’s (Melin & Nannfeldt 1934). We observed a wider range of conidial lengths (1.5–5 µm) but mean dimensions (2.5–1.5 µm) were similar to Robak’s (Melin & Nannfeldt 1934). Our measurements for O. griseum fall between the measurements we obtained for O. fuscum and those given in the original description (Robak 1932). In general, the isolates of O. griseum have longer conidiophores (25–130 µm) than the ex-type of O. fuscum (15–40 µm). Conidia of O. griseum also differ from those of O. fuscum under SEM. Our isolates of O. griseum have relatively long (1.5–5 µm), cylindrical conidia with an asperulate perispore while O. fuscum has relatively short (1.5–3 µm), subglobose to ellipsoidal, dimpled conidia with an asperulate to minutely verruculose perispore. Additional cultural 108 and molecular differences between O. fuscum and O. griseum (Sigler & Gibas 2005–this volume) support recognizing them as distinct. 14. Oidiodendron hughesii Udagawa & Uchiyama, Can. J. Bot. 76: 1641–1643. 1998. Figs 34–39. = Oidiodendron reticulatum Calduch et al. (2004) Colonies on PCA 12–13 mm diam at 21 d at 15 ºC, 3–4 mm diam at 21 d at 25 ºC, green-grey, becoming dark green to olivaceous black with age, appressed; reverse uncoloured to brown-grey; exudates absent. Conidia abundant after 14 d. Colonies on OA growing more slowly than on PCA, bearing conidiophores in dense stands; reverse red-brown. Conidiophores erect, 60–100 × 2.5–3 µm, melanized, unbranched and smooth-walled below and asperulate and darkened above, branched and anastomosed to form a globose to subglobose reticulate network (60–160 µm diam; 250– 280 µm diam when peripheral spines are included). OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Figs 34–39. Oidiodendron hughesii. Reproduced with permission from Udagawa & Uchiyama 1998 and Calduch et al. 2004. Conidiophore and reticulum of asperulate appendages surrounding a conidial mass (O. reticulatum; Calduch et al. 2004, ﬁg. 24). Bar = 30 µm. 35. Conidiophore and reticulum of smooth to asperulate appendages surrounding a conidial mass (O. hughesii; Udagawa & Uchiyama 1998, ﬁg. 11). Bar = 50 µm. 36. Simple conidiophore bearing chains of asperulate to spinulose, ellipsoidal conidia (O. hughesii; Udagawa & Uchiyama 1998, ﬁg. 17). Bar = 10 µm. 37. Appendages of the reticulum surrounding the conidial mass. Note that the asperulate ornamentation does not extend to the apices (O. hughesii; Udagawa & Uchiyama 1998, ﬁg. 14). Bar = 50 µm. 38. Asperulate hyphae of the reticulum surrounding the conidial mass. Note that the asperulate ornamentation of the hyphae extends almost to the apices, but that the tips of the hyphae are smooth (O. reticulatum; Calduch et al. 2004, ﬁg. 27). Bar = 10 µm. 39. Ellipsoidal, asperulate to spinulose conidia (O. reticulatum; Calduch et al. 2004, ﬁg. 31). Bar = 2 µm. Peripheral spines appendage-like, septate, dark olive brown, basally asperulate, with 1–2 branchlets arising near base; apices pointed, lighter in colour and smoother than the basal region. Fertile hyphae, 1.5–2.5 µm diam, arising from lateral branches of reticulum elements, verticillate, hyaline, smooth-walled, fragmenting to produce conidia. Conidia hyaline to pale olivebrown en masse, oval to ellipsoidal, thick-walled, asperulate, 2–4 × 1.5–2.5 µm. Simple conidiophores also produced, melanized, smooth, branched at apex to produce a dense head of fertile hyphae. Optimal growth at 15 °C. Habitat: forest soil. Description is from Udagawa & Uchiyama (1998). optima. In O. reticulatum, the appendages are verruculose along their entire length while in O. hughesii they are smooth at their apices. The conidia of O. reticulatum are described as pale brown to olivaceous (Calduch et al. 2004) while those of O. hughesii are described as hyaline to pale olive brown en masse (Udagawa et al. 1998). These differences are slight in light of the similarities between the two species in colony morphology, reticulum dimensions, and conidial size, shape, and ornamentation (Udagawa et al. 1998, Calduch et al. 2004). These minor differences become even less credible considering that both species are monotypic. Differences in appendage ornamentation and conidial size could reﬂect either intraspeciﬁc variation among isolates or differences in developmental stage. Calduch et al. (2004) report that O. reticulatum grows optimally at 25 °C while O. hughesii grows optimally at 15 °C. However, they also note that, on some media, growth of O. reticulatum is similar at 15 and 25 °C (Calduch et al. 2004). It is plausible that this physiological difference has been overstated and is due to ecological rather than phylogenetic differences. Udagawa et al. (1998) isolated O. hughesii from a cool, temperate, alpine site while Calduch et al. (2004) isolated O. reticulatum from a warm, subtropical site in Spain. We feel that the differences between O. hughesii and O. reticulatum are not signiﬁcant at the species level and suggest they are synonymous. There are no sequence data for O. hughesii. Oidiodendron hughesii, O. muniellense, and O. setiferum are the only species bearing appendages at the apex of the conidiophore. In O. hughesii, the appendages are highly branched and anastomose to form a reticuloperidium-like structure that encloses the arthroconidial mass, while in the other two species appendages are more sparsely branched and antlerlike. 15. Oidiodendron maius var. citrinum (Barron) Rice & Currah, stat. nov., MycoBank MB500256, Figs 40–41. ≡ Oidiodendron citrinum Barron, Can. J. Bot. 40: 597. 1962 (basionym). Notes: Calduch et al. (2004) distinguish O. reticulatum from O. hughesii on the basis of appendage ornamentation, conidial colour, and temperature Figs 40–41. Oidiodendron maius var. citrinum (UAMH 1525). 40. Tall, erect conidiophore bearing a branched head of fertile hyphae that fragment to form long chains of subglobose to elongate conidia. Bar = 15 µm. 41. Subglobose to elongate conidia with a rugose perispore. Bar = 1 µm. 109 RICE & CURRAH Colonies on CMA 30–36 mm diam at 28 d, yellowgreen, appressed; reverse pale brown to dark brown in the centre. Conidiophores abundant, bearing masses of yellow conidia, tall, unbranched, melanized, smooth, 50–(120)–230 × 2–4 µm. Fertile hyphae hyaline, 2–3 µm diam, dichotomously branched, fragmenting to form long, undulating chains of conidia. Conidia thinwalled, hyaline, subglobose to elongate, 1.5–(2.8)–5 × 1–(1.8)–2.5 µm, with a rugose perispore. Maximal growth at pH 3–5 and 20 ºC. Degrades cellulose, gelatin, lipid, pectin, starch, tannic acid, and lignin. Specimens examined: Canada, Guelph, Ontario, soil, cedar bog, Barron (UAMH 1525, ex-type O. citrinum); 6 Mile Lake, Muskoka District, Ontario, ex black sclerotia in stream drift, March 1991, Malloch (UAMH 7089); Slave Lake, Alberta, ex black mycorrhizal root tip (Cenococcum Moug. & Fr. sp.) of Arctostaphylos uva-ursi, Pinus banksiana stand on sand dune, 1998, Hambleton (UAMH 9275). Notes: Oidiodendron citrinum is sufﬁciently similar to O. maius that it can be considered a subspeciﬁc taxon within O. maius, which was described in the same publication (Barron 1962). Oidiodendron maius is much more common in the literature and is given priority. These two taxa are recognized at the varietal level, rather than as subspecies, because the latter term implies the existence of intermediate forms and differences in distribution (Hawksworth 1974). There are few data concerning the distribution and/or possible intergradation of these taxa that would support designating them as subspecies. The conidiophores and conidia are similar to O. maius var. maius but the two can be distinguished on the basis of colony colour, conidial ornamentation under SEM, and WDG reaction. Oidiodendron maius var. citrinum has yellow colonies, conidia with a rugose perispore, and a positive WDG reaction while O. maius var. maius has white colonies, conidia with an asperulate perispore, and a negative WDG reaction. Molecular analyses indicate that these differences are probably not signiﬁcant at the species level leading to the suggestion that O. citrinum and O. maius are conspeciﬁc or that O. citrinum is a subspecies of O. maius (Hambleton et al. 1998, Lacourt et al. 2001, Sigler & Gibas 2005–this volume). Additional morphological (Sigler & Gibas 2005–this volume) and physiological (Rice & Currah 2005–this volume) characters support a close relationship between these taxa. 16. Oidiodendron maius var. maius (Barron) Rice & Currah, Figs 42–45. ≡ Oidiodendron maius Barron, Can. J. Bot. 40: 600–602. 1962. Colonies on CMA 29–38 mm diam at 28 d, off-white to grey, appressed; reverse pale grey to dark brown in 110 Figs 42–45. Oidiodendron maius var. maius. 42. Extremely tall conidiophore bearing a head of divergent, branched, undulating chains of thin-walled, subglobose to elongate or cylindrical conidia (UAMH 9749). Bar = 40 µm. 43. Conidiophore apex branching to form fertile hyphae that fragment to form chains of subglobose to elongate conidia (UAMH 10460). Bar = 10 µm. 44. Chains of asperulate, elongate conidia with connectives visible between the conidia (UAMH 8920). Bar = 1 µm. 45. Branching chain of asperulate conidia with scars (arrow) showing position of side branches that have broken free (UAMH 8920). Bar = 1 µm. centre. Conidiophores abundant, tall, dark, bearing masses of white conidia, unbranched, smooth, 70– (185)–390 × 2–4 µm. Fertile hyphae hyaline, 2–3 µm diam, dichotomously branched, fragmenting into long, undulating chains of conidia. Conidia thin-walled, hyaline, subglobose to elongate, 2–(3.3)–5 × 1–(1.7)– 2.5 µm, with an asperulate perispore. Maximal growth at pH 3 and 20 ºC. Degrades cellulose, gelatin, lipid, pectin, starch, and tannic acid. Specimens examined: Canada, Ontario, soil, cedar bog, Barron (UAMH 1540, ex-type); Alberta, roots Oxycoccus quadripetalus Gilib, Picea mariana Miller bog, Hambleton (UAMH 8920); Perryvale, Alberta, decomposing Sphagnum fuscum, bog, Thormann (UAMH 9749); Fort McKay, Alberta, roots Vaccinium myrtilloides, disturbed sand hill, Hill-Rackette (UAMH 10460). Finland, Kevo, Research Station, roots Vaccinium vitis-idaea L., Betula L.-dominated fjell, Currah (UAMH 10461). Notes: O. maius var. maius is the only species in the genus conﬁrmed to act as an ericoid mycorrhizal partner in nature. It can be distinguished from morphologically similar species, including O. fuscum, O. griseum, and the anamorphs of M. arcticum and M. emodense, by OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM its loose head of highly undulating chains of white conidia, and its long conidiophores (mean >100). The other species have less undulant fertile hyphae that branch at more acute angles, resulting in denser conidial heads, and mean conidiophore lengths less than 100 µm. 17. Oidiodendron muniellense Calduch, Stchigel, Gené & Guarro, Stud. Mycol. 50: 161–163. 2004. Figs 46–48. Colonies on decaying basidiome effuse, hairy, greenish brown, with the melanized mycelium (hyphae 1–2 µm wide, septate) partially immersed in the substrate. Colonies on OA 30–35 mm diam at 4 wk at 25 °C, brownish beige to brown, ﬂat, velvety, irregularly folded; reverse dark brown; brownish orange diffusible pigment produced. Colonies on PCA 26–30 mm at 4 wk at 25 °C, olive-brown, ﬂat; reverse olive-brown. Colonies on PDA 37–40 mm diam at 4 wk at 25 °C, greyish orange to greyish brown, slightly funiculose at centre, radially folded; reverse brownish orange to yellowish brown. Conidiophores erect, melanized, up to 200 µm long, 2–3.5 µm wide; upper part bearing 4–6 verticillate appendages. Appendages several times dichotomously or trichotomously branched, straight, up to 60 µm long, 1.5–2.5 µm wide at the base, melanized, thick-walled, septate, and smooth at the base, becoming pale, thin-walled, and roughened at the pointed tips. Fertile hyphae terminal or lateral on the conidiophore apex and appendages, branched, hyaline, smooth-walled, 1–2.5 µm wide, fragmenting to form chains of conidia. Conidia globose to subglobose, ochraceous, 1.5–2.5 µm diam, covered with Figs 46–48. Oidiodendron muniellense. Reproduced with permission from Calduch et al. 2004. 46. Conidiophore bearing straight, branched, melanized appendages and a conidial mass. Bar = 50 µm. 47. Conidiophores bearing branched, melanized, fertile appendages. Bar = 40 µm. 48. Globose to subglobose conidia with a reticulate network of spines. Bar = 5 µm. a reticulate network of spines as seen under SEM. Optimal growth at 25 °C. Habitat: decaying basidiome, Spain. Description is from Calduch et al. (2004). Notes: This species is morphologically most similar to O. setiferum but the appendages of O. muniellense are straighter than those of O. setiferum and are rough at the tips while those of O. setiferum are smooth. The conidia of O. muniellense are globose to subglobose and covered by a reticulate network of spines, causing them to appear asperulate to echinulate under light microscopy while those of O. setiferum are subglobose to ovoid or elongate with a central dimple and covered with a rugose perispore that causes them to appear faintly ornamented to smooth under light microscopy. Notably, the conidia of O. tenuissimum, a species suggested by molecular evidence to be closely related to O. muniellense, are very similar to those of that species: melanized, subglobose, and covered with a reticulate network of spines. 18. Oidiodendron myxotrichoides Calduch, Gené & Guarro, Stud. Mycol. 47: 217–218. 2002. Figs 49–50. Colonies on beech leaves effuse, greenish-brown, forming patches. Hyphae pale brown to brown, septate, branched, 1.5–2.5 µm wide. Colonies on OA 30–35 mm diam at 4 wk at 15 ºC, grey-violet to violet, ﬂat, granulose; reverse dull violet to dark violet. Colonies on PCA 20–28 mm diam at 4 wk at 15 ºC, green-grey at the center with white to grey-white margins; reverse green-grey to dark green. Colonies on MEA 21–29 mm diam at 4 wk at 15 ºC, violet-grey to dark violet, velvety and radially folded, reverse violet-grey to dark violet. Colonies on PDA 28–35 mm diam at 4 wk at 15 ºC, grey-green, fasciculate, producing a light orange to grey-orange diffusible pigment; reverse dark brown. Conidiomata grey-green to olive, abundant, arranged in concentric circles on OA and PCA, towards the periphery on MEA, absent on PDA. Conidiomata superﬁcial, solitary, conﬂuent, brown to dark brown, spherical to subspherical, up to 490 µm diam, consisting of a reticulate network of septate, brown, thick- and smooth- walled, branched and anastomosed hyphae up to 4.5 µm wide, radially disposed, from which fertile hyphae are produced. Peripheral hyphae up to 250 µm long, spine-like, straight, usually with shorter and deﬂected lateral branches, brown to dark brown, paling towards the apex, smooth- and thickwalled, 2–4 µm wide. Conidiophores of arborescent fertile hyphae that arise laterally or terminally from the melanized hyphae of the reticulum, subhyaline, 2–3 µm wide, smooth- and thin- walled. Conidia globose, subglobose, or broadly ellipsoidal, pale brown, smooth-walled or very ﬁnely rugose and thickwalled at maturity, 2–3 × 1.5–2.5 µm. Optimal growth at 15 ºC; growth and sporulation reduced at 25 ºC; no 111 RICE & CURRAH Figs 49–50. Oidiodendron myxotrichoides. Reproduced with permission from Calduch et al. 2002. 49. Sessile, reticuloperidium-like conidioma supporting fertile hyphae that fragment to produce ellipsoidal conidia. Bar = 50 µm. 50. Ellipsoidal conidia with a rugose perispore with connectives visible between some of the conidia. Bar = 2 µm. growth at 37 ºC. Habitat: Fagus sylvatica leaf, Santa Fe del Montseny, Montseny Natural Park, Catalonia, Spain. Description from Calduch et al. (2002). The description of O. myxotrichoides appeared while this manuscript was nearly complete and isolates were not examined. Notes: The conidiomata of O. myxotrichoides are described as sporodochia by Calduch et al. (2002); however, this term is inappropriate because the conidiomata lack basal pads of pseudoparenchyma and do not consist of masses of short conidiophores (Hawksworth et al. 1995). The structure is probably best referred to simply as a conidioma. Oidiodendron myxotrichoides is similar to O. hughesii in producing conidia within a reticuloperidium-like structure but in O. hughesii the reticulum forms from anastomosed appendages at the apex of a solitary conidiophore. 19. Oidiodendron periconioides Morrall, Can. J. Bot. 46: 204–205. 1968. Figs 51–53. Colonies on CMA 11–18 mm diam at 28 d, dark greengrey to brown; reverse dark red-brown. Orange-brown exudate produced. Aerial hyphae and conidiophores abundant. Conidia green-grey to brown en masse. Conidiophores smooth, melanized and unbranched at base becoming hyaline and branched at apex, 25– (85)–175 × 2–4 µm. Fertile hyphae hyaline, branched, swollen to form chains of vesicles that fragment to become chains of conidia arising at the conidiophore apices or laterally from vegetative hyphae. Conidia thick-walled, dark, spiny at maturity, globose to ellipsoidal, 3–(3.7)–6 × 2–(3.1)–4 µm. Maximal growth at pH3 and 20 ºC. Degrades cellulose, gelatin, pectin (UAMH 6084, UAMH 8527), starch and tannic acid. Specimens examined: Canada, Candle Lake, Saskatchewan, boreal forest soil, 1964, Morrall (UAMH 8527, ex-type); Nichol Springs, Cypress Hills, Alberta, root endophyte, Calypso bulbosa (L.) Oakes, May 1987, Hambleton (UAMH 6084). Japan, humus, Currah (UAMH 7289). 112 Figs 51–53. Oidiodendron periconioides (UAMH 8527). 51. Erect conidiophore bearing a dense head of dark, spinulose, subglobose to ellipsoidal conidia. Bar = 20 µm. 52. Short chains of spinulose, subglobose to ellipsoidal conidia forming from swollen vesicles (arrows). Bar = 5 µm. 53. Spinulose, globose to ellipsoidal conidia. Bar = 1 µm. Notes: Oidiodendron periconioides is unique in the genus because it produces chains of globose, vesiclelike swellings that precede the appearance of conidia in short conidiogenous branches. It is also the only species of Oidiodendron that consistently produces dark, spiny, globose to ellipsoidal conidia. Oidiodendron echinulatum is similar but has more ellipsoidal conidia with rounded warts on the perispore; it is also WDG positive while O. periconioides is WDG negative. 20. Oidiodendron pilicola Kobayasi, Bull. Natl. Sci. Mus. (Tokyo) 12: 424–425. 1969. Fig. 54. Conidiophores simple, erect, septate, thick-walled, pale olivaceous brown, 100–150 × 2.5–4 µm. Upper part branched monopodially (laterally and oppositely) into fertile hyphae. Fertile hyphae (1.5–2.5 µm diam), 2–3 × branched, hyaline, fragmenting to form conidia. Conidia hyaline, barrel-shaped, truncate with frills at both ends, smooth, catenate, apically or laterally produced, forming dense clusters, 3–3.5 × 1.5–2 µm. Habitat: decaying human hair; soil. Description from Kobayasi (1969). Specimen examined: Sweden, forest soil, 1972, Nylund (UAMH 7526). Degenerate and not producing conidia. Notes: Oidiodendron pilicola resembles O. truncatum, and the anamorphs of M. cancellatum and M. striatosporum, in producing conidia that are truncate at both ends. Conidia of O. pilicola are hyaline, while those of O. truncatum and M. striatosporum are dark. Oidiodendron truncatum and M. cancellatum conidia differ by being reticulate, not smooth, and M. striatosporum conidia differ by being asperulate. OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Fig. 54. Oidiodendron pilicola. Reconstructed from descriptions and illustrations given by Kobayasi (1969). A tall conidiophore bears oppositely branched, fertile hyphae that fragment to form branched chains of hyaline, smooth, barrel-shaped conidia with apical frills. No information was given to allow placement of septa in the conidiophore stipe in this conceptual drawing. Bar = 15 µm. Molecular evidence suggests that this species is distinct but close to O. chlamydosporicum (Hambleton, unpubl. data). 21. Oidiodendron rhodogenum Robak, Saertryk av Nyt Mag. Naturvidensk. 71: 251–255. 1932. Figs 55– 58. Colonies on CMA 31–34 mm diam at 28 d, off-white to grey, appressed; reverse brown to grey-brown. Red diffusible pigment absent on CMA but produced by UAMH 1405 on OA. Conidiophores abundant, bearing masses of off-white conidia, smooth, branched, melanized, 30–(50)–85 × 3–6 µm. Fertile hyphae hyaline, 2–5 µm diam, dichotomously branched, fragmenting into long chains of conidia. Conidia hyaline to lightly melanized, subglobose to elongate and irregular, 1.5–(2.5)–5 × 1.5–(1.6)–2 µm, with a rugose perispore. Maximal growth at pH3 and 20 ºC. Degrades cellulose, gelatin, pectin, and starch. Specimens examined: Norway, Kistefoss Mills, sludge in pulp strainers, 1929, H. Robak (UAMH 1405, authentic). Canada, Ontario, forest soil, 1969, Barron (CBS 401.69 = UAMH 8508). Notes: O. rhodogenum has been identiﬁed traditionally on the basis of a red diffusible pigment in culture but this character is unreliable; pigment production is Figs 55–58. Oidiodendron rhodogenum (UAMH 1405). 55. Erect, dichotomously branched conidiophore bearing divergent, branched chains of thin-walled, subglobose to elongate or cylindrical conidia. Bar = 15 µm. 56. Short chains of ellipsoidal to elongate conidia branching off a portion of the conidiophore. Conidia have a rugose perispore. Bar = 5 µm. 57. Chains of ellipsoidal to elongate or cylindrical conidia with a rugose perispore and connectives visible between conidia. Bar = 1 µm. 58. Rugose, ellipsoidal to elongate conidia branching from a fertile hypha. Note scars left by conidia that have broken free. Bar = 1 µm. inconsistent within and among isolates. In the absence of the red pigment, O. rhodogenum is difﬁcult to identify because the species is not distinctive morphologically or physiologically. Oidiodendron fuscum and O. griseum are similar but have unbranched conidiophores. In addition, the conidia of O. rhodogenum are elongate to cylindrical with a rugose perispore while those of O. griseum are asperulate and those of O. fuscum are dimpled, asperulate, and subglobose to ellipsoidal. 22. Oidiodendron setiferum Udagawa & Toyazaki, Mycotaxon 28: 234–238. 1987. Figs 59–65. = Oidiodendron ramosum Calduch et al. (2004) Colonies on CMA 23–25 mm diam at 28 d, brown, appressed; reverse green-grey to black (darkest under areas of conidial production). Conidiophores abundant, bearing brown masses of conidia and appendages, smooth, melanized, branching at apex to form appendages and fertile hyphae, 40–(80)–180 × 2–3 µm. Fertile hyphae hyaline, penicillate, borne either at the conidiophore apex or at the tips or branching points of the appendages, and forming a dense head of conidia. Appendages (2–4 per conidiophore) produced at the apices of the conidiophores and subtending masses 113 RICE & CURRAH of conidia, dichotomously branched, melanized, with tapered apices, 20–100 × 2–3 µm. Conidia thin-walled, hyaline to lightly pigmented, subglobose to elongate or irregular, 1.5–(2.5)–4 × 1–(1.5)–2.5 µm, with a rugose perispore and a central dimple under SEM. Maximal growth at 25 ºC and pH 3. Degrades cellulose, gelatin, pectin, starch and tannic acid. Specimen examined: Japan, Kobe, house dust, Udagawa (UAMH 5715, ex-type). Figs 59–65. Oidiodendron setiferum (UAMH 5715) or reproduced with permission from Calduch et al. 2004. 59. Erect conidiophore bearing two dichotomously branched appendages and a dense head of thin-walled, hyaline to lightly pigmented, subglobose to elongate or irregular conidia (UAMH 5715). Bar 15 = µm. 60. Conidiophores bearing long, branched, recurved appendages subtending central conidial masses (O. ramosum; Calduch et al. 2004, ﬁg. 12). Bar = 100 µm. 61. Apex of conidiophore bearing four dichotomously branched, recurved, fertile appendages and a small central conidial mass. Arrows indicate fertile hyphae arising from the appendages (UAMH 5715). Bar = 10 µm. 62. Fertile appendages with conidia arising from branching points and apices (UAMH 5715). Bar = 10 µm. 63. Penicillate head of fertile hyphae fragmenting to form short chains of subglobose to ellipsoidal or elongate conidia with a rugose perispore. Connectives are visible between the conidia (UAMH 5715). Bar = 1 µm. 64. Chains of subglobose to ellipsoidal conidia with a rugose perispore and central dimple visible on some conidia (UAMH 5715). Bar = 1 µm. 65. Subglobose to ellipsoidal conidia with a rugose perispore and a central dimple visible on some conidia (O. ramosum; Calduch et al. 2004, ﬁg. 18). Bar = 1.75 µm. 114 OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Notes: Calduch et al. (2004) distinguished O. ramosum from O. setiferum on the basis of the fertility of the appendages and conidial ornamentation. Oidiodendron setiferum was described as having sterile appendages surrounding the fertile head (Udagawa & Toyazaki 1987) while in O. ramosum, the appendages often give rise to fertile hyphae from their branching points or apices (Calduch et al. 2004). Although the matter is not noted in the original description of O. setiferum, our SEM observations of the ex-type show that fertile hyphae and conidia arise from the branching points and apices of the appendages. The conidia of O. ramosum are described as smooth to slightly roughened (Calduch et al. 2004) and those of O. setiferum are smooth (Udagawa & Toyazaki 1987). However, SEM examination of O. setiferum shows that the conidia have a rugose perispore and are no less roughened than the O. ramosum conidia depicted in the SEM images of Calduch et al. (2004). Thus, the differences noted by Calduch et al. (2004) between the original description of O. setiferum and the features of their taxon, O. ramosum, cannot be substantiated and O. ramosum is here considered a synonym of O. setiferum. The two taxa group together with low to moderate bootstrap support (54) based on ITS sequence data, suggesting a close relationship rather than conﬁrming their distinctness as suggested by Calduch et al. (2004). Oidiodendron setiferum, O. muniellense and O. hughesii can be distinguished from others in the genus by the melanized appendages that subtend the arthroconidia. See comments under O. hughesii and O. muniellense. 23. Oidiodendron tenuissimum (Peck) Hughes, Can. J. Bot 36: 790. 1958. Figs 66–69. ≡ Periconia tenuissima Peck ﬁde Hughes (1958). Colonies on CMA 18–22 mm diam at 28 d, pale brown, appressed; reverse dark grey-brown to black. Conidiophores abundant, arranged in concentric rings, bearing masses of brown conidia, unbranched, melanized, 30–(95)–240 × 2–4 µm. Fertile hyphae hyaline, dichotomously branched, fragmenting to form chains of conidia. Conidia melanized at maturity, faintly ornamented, subglobose to elongate, 2–(2.5)– 4 × 1–(2.1)–3 µm. Conidia covered by a reticulate network of spines as revealed by SEM. Maximal growth at pH 3–5 and 20 ºC. Degrades cellulose, gelatin, lipid, pectin, and starch. Specimens examined: Spain, La Gomera, Canary Islands, leaf litter, 1995, Castañeda (UAMH 8513). Canada, Guelph, Ontario, soil, mixed deciduous forest, 1960, Barron (UAMH 1523). Notes: See also discussions under O. fuscum and O. griseum. Both UAMH 8513 and 1523, the two strains listed above, had previously been identiﬁed as O. tenuissimum sensu Barron, but were subsequently considered distinct from that species on the basis of ITS sequences and were labelled “O. sp. nov” (Hambleton et al.1998). Closer comparison of these isolates with the type material of Periconia tenuissima shows that they are indistinguishable from it and are best accommodated under the name O. tenuissimum. Oidiodendron tenuissimum has brown colonies, conidiophores that may exceed 200 µm, and dark, spinulose conidia as opposed to the off-white or pale grey colonies, shorter conidiophores (typically less than 100 µm long), and hyaline, minutely verruculose to asperulate conidia of O. fuscum. It can be distinguished from other species of Oidiodendron by the dark, subglobose to ellipsoidal or elongate conidia with a reticulate network of spines. 24. Oidiodendron truncatum Barron, Can. J. Bot. 40: 602–604. 1962. Figs 70–72. Colonies on CMA 30–32 mm diam (UAMH 8443), 38–42 mm diam (UAMH 1399, UAMH 10464), brown to green-grey, appressed; reverse green-grey to brown. Conidiophores abundant, clumped, bearing masses of brown conidia, smooth, branched at apex, more or less melanized, 18–(75)–180 × 2–4 µm. Conidia dark at maturity, produced in branched chains at the conidiophore apices or from vegetative hyphae, barrelshaped to irregular, truncate with distinct apical scars and reticulate ornamentation, 2–(3.6)–5 × 1–(2.5)–3.5 µm. Maximal growth at 15–20 ºC and pH >7. Degrades cellulose, gelatin, lipid, and pectin. Specimens examined: Canada, Guelph, Ontario, soil, mixed forest, 1960, Barron (UAMH 1399, ex-type); Slave Lake, Alberta, decaying spruce wood, Lumley (UAMH 10464). Italy, soil of snow valley, Mosca (UAMH 8443 = ATCC 36256, as O. ambiguum). Notes: This species can be readily distinguished from others in the genus because of its dark, reticulate, truncate conidia and its inability to degrade starch. Excluded Species Oidiodendron robustum Mercado Sierra & Castañeda Ruiz, Acta Bot. Cubana 33: 3–4. 1985. The type specimen for this species was not examined but its description lists conidiophores that are 250– 870 × 7.5–10.5 µm and conidia 5–11 × 2.5–3.2 µm (Mercado Sierra & Castañeda Ruiz 1985). Both are much larger than all other species of Oidiodendron and are more reminiscent of species of Cladosporium. From the original illustrations and description it is impossible to determine whether the chains of conidia are forming by basipetal fragmentation or acrogenous budding. Based on these ambiguities, this taxon is excluded from the genus. 115 RICE & CURRAH Figs 66–69. Oidiodendron tenuissimum. 66. Erect conidiophore bearing a dense head of thick-walled, dark, subglobose to elongate conidia (UAMH 8513). Bar = 15 µm. 67. Short conidiophore bearing a large, dense head of long chains of spinulose, subglobose conidia (UAMH 8513). Bar = 10 µm. 68. Spinulose, subglobose to ellipsoidal conidia of dried type material (NYS). Bar = 2 µm. 69. Subglobose to ellipsoidal conidia with a reticulate network of spines (UAMH 8513). Bar = 1 µm. 116 OIDIODENDRON: SURVEY OF THE NAMED SPECIES AND RELATED ANAMORPHS OF MYXOTRICHUM Figs 70–72. Oidiodendron truncatum. 70. Erect conidiophore bearing a large, dense head of thick-walled, truncate, dark, barrelshaped conidia with apical frills (UAMH 1399). Bar = 15 µm. 71. Branched chains of barrel-shaped conidia with a rugose (reticulate) perispore (UAMH 10464). Bar = 5 µm. 72. Barrel-shaped conidia with a reticulate perispore (UAMH 10464). Bar = 1 µm. Oidiodendron terrestre Roy & Singh, J. Indian Bot. Soc. 48: 158–159. 1969. This species is described as having rapid growth (90 mm in 3 d), hyaline conidiophores, chlamydospores 4.5–14 × 3.5–12.5 µm and ellipsoidal to cylindrical, one-to two-celled conidia 4–15 × 3–13 µm (Roy & Singh 1969). This growth rate is much greater, and conidia much larger than observed in other Oidiodendron species. In addition, two-celled conidia are inconsistent with the generic diagnosis. Conidial ontogeny is unclear from the original description and illustrations but appears blastic and acropetal rather than basipetal. The absence of deﬁnitive Oidiodendron characters, along with the large, two-celled conidia, rapid growth, and hyaline conidiophores, easily exclude this species from Oidiodendron. ACKNOWLEDGEMENTS We thank David Beyer and Joost Stalpers for providing information on “O. sindenia” and O. sulphureum, respectively. George Braybrook assisted with SEM. Sarah Hambleton sequenced several isolates and kindly shared unpublished phylogenetic trees and SEM images. Lynne Sigler provided UAMH cultures and permanent slides and commented on an early ms. draft. Lindsay Elliott, Melissa Day, Ben Wilson, and Marcie Plishka provided laboratory assistance. 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