Competing sexual and asexual generic names in Pucciniomycotina and Ustilaginomycotina (Basidiomycota) and recommendations for use

Diversity of colacosome-interacting mycoparasites expands the understanding of the evolution and ecology of Microbotryomycetes

Mycoparasites in Basidiomycota comprise a diverse group of fungi, both morphologically and phylogenetically. They interact with their hosts through either fusion-interaction or colacosome-interaction. Colacosomes are subcellular structures formed by the mycoparasite at the host-parasite interface, which penetrate the parasite and host cell walls. Previously, these structures were detected in 19 fungal species, usually by means of transmission electron microscopy. Most colacosome-forming species have been assigned to Microbotryomycetes (Pucciniomycotina, Basidiomycota), a highly diverse class, comprising saprobic yeasts, mycoparasites, and phytoparasites. In general, these myco- and phytoparasites are dimorphic organisms, with a parasitic filamentous morph and saprobic yeast morph. We investigated colacosome-forming mycoparasites based on fungarium material, freshly collected specimens, and cultures of yeast morphs. We characterised the micromorphology of filamentous morphs, the physiological characteristics of yeast morphs, and inferred phylogenetic relationships based on DNA sequence data from seven loci. We outline and employ an epifluorescence-based microscopic method to assess the presence and organisation of colacosomes. We describe five new species in the genus Colacogloea, the novel dimorphic mycoparasite Mycogloiocolax gerardii, and provide the first report of a sexual, mycoparasitic morph in Colacogloea philyla and in the genus Slooffia. We detected colacosomes in eight fungal species, which brings the total number of known colacosome-forming fungi to 27. Finally, we revealed three distinct types of colacosome organisation in Microbotryomycetes. Taxonomic novelties and typifications: New family: Mycogloiocolacaeae Schoutteten & Yurkov; New genus: Mycogloiocolax Schoutteten & Rödel; New species: Colacogloea bettinae Schoutteten & Begerow, C. biconidiata Schoutteten, C. fennica Schoutteten & Miettinen, C. microspora Schoutteten, C. universitatis-gandavensis Schoutteten & Verbeken, Mycogloiocolax gerardii Schoutteten & Rödel; New combinations: Slooffia micra (Bourdot & Galzin) Schoutteten, Fellozyma cerberi (A.M. Yurkov et al.) Schoutteten & Yurkov, Fellozyma telluris (A.M. Yurkov et al.) Schoutteten & Yurkov; Epitypifications (basionyms): Achroomyces insignis Hauerslev, Platygloea micra Bourdot & Galzin, Platygloea peniophorae Bourdot & Galzin; Lectotypification (basionym): Platygloea peniophorae Bourdot & Galzin Citation: Schoutteten N, Yurkov A, Leroux O, Haelewaters D, Van Der Straeten D, Miettinen O, Boekhout T, Begerow D, Verbeken A (2023). Diversity of colacosome-interacting mycoparasites expands the understanding of the evolution and ecology of Microbotryomycetes. Studies in Mycology 106: 41-94. doi: 10.3114/sim.2022.106.02.

Insights into Diversity, Distribution, and Systematics of Rust Genus Puccinia

Puccinia, which comprises 4000 species, is the largest genus of rust fungi and one of the destructive plant pathogenic rust genera that are reported to infect both agricultural and nonagricultural plants with severe illnesses. The presence of bi-celled teliospores is one of the major features of these rust fungi that differentiated them from Uromyces, which is another largest genus of rust fungi. In the present study, an overview of the current knowledge on the general taxonomy and ecology of the rust genus Puccinia is presented. The status of the molecular identification of this genus along with updated species numbers and their current statuses in the 21st century are also presented, in addition to their threats to both agricultural and nonagricultural plants. Furthermore, a phylogenetic analysis based on ITS and LSU DNA sequence data available in GenBank and the published literature was performed to examine the intergeneric relationships of Puccinia. The obtained results revealed the worldwide distribution of Puccinia. Compared with other nations, a reasonable increase in research publications over the current century was demonstrated in Asian countries. The plant families Asteraceae and Poaceae were observed as the most infected in the 21st century. The phylogenetic studies of the LSU and ITS sequence data revealed the polyphyletic nature of Puccinia. In addition, the presences of too short, too lengthy, and incomplete sequences in the NCBI database demonstrate the need for extensive DNA-based analyses for a better understanding of the taxonomic placement of Puccinia.

A Global Overview of Diversity and Phylogeny of the Rust Genus Uromyces

Uromyces is the second-largest plant pathogenic rust genus, is responsible for numerous diseases, and has major effects on both agricultural and non-agricultural plants. The genus is generally characterized by its unicellular teliospores that help to characterize it and distinguish it from another important rust genus, Puccinia. In this study, a global overview of the diversity and distribution of Uromyces is presented based on both online and offline resources. The information obtained was analyzed for numerical and graphical summaries to provide the diversity and distribution of the genus by country and continent. Besides this, broad taxonomical aspects, a brief life cycle, and other comparative aspects on diversity and distribution were also provided. In addition, a phylogenetic analysis based on the ITS and nLSU DNA sequence data available in GenBank and published literature was performed to examine the intergeneric relationships of Uromyces. The results obtained revealed that the rust genus is found distributed over 150 countries, territories, and occupancies of the world on around 647 plant genera belonging to 95 plant families. Phylogenetic studies based on LSU and ITS sequence data revealed that Uromyces species are polyphyletic and require more DNA-based analyses for a better understanding of their taxonomic placement.

Sporobolomyces lactucae sp. nov. (Pucciniomycotina, Microbotryomycetes, Sporidiobolales): An Abundant Component of Romaine Lettuce Phylloplanes

Shifts in food microbiomes may impact the establishment of human pathogens, such as virulent lineages of Escherichia coli, and thus are important to investigate. Foods that are often consumed raw, such as lettuce, are particularly susceptible to such outbreaks. We have previously found that an undescribed Sporobolomyces yeast is an abundant component of the mycobiome of commercial romaine lettuce (Lactuca sativa). Here, we formally describe this species as Sporobolomyces lactucae sp. nov. (Pucciniomycotina, Microbotryomycetes, and Sporidiobolales). We isolated multiple strains of this yeast from commercial romaine lettuce purchased from supermarkets in Illinois and Indiana; additional isolates were obtained from various plant phylloplanes in California. S. lactucae is a red-pigmented species that is similar in appearance to other members of the genus Sporobolomyces. However, it can be differentiated by its ability to assimilate glucuronate and D-glucosamine. Gene genealogical concordance supports S. lactucae as a new species. The phylogenetic reconstruction of a four-locus dataset, comprising the internal transcribed spacer and large ribosomal subunit D1/D2 domain of the ribosomal RNA gene, translation elongation factor 1-α, and cytochrome B, places S. lactucae as a sister to the S. roseus clade. Sporobolomyces lactucae is one of the most common fungi in the lettuce microbiome.

Current Insight into Traditional and Modern Methods in Fungal Diversity Estimates

Fungi are an important and diverse component in various ecosystems. The methods to identify different fungi are an important step in any mycological study. Classical methods of fungal identification, which rely mainly on morphological characteristics and modern use of DNA based molecular techniques, have proven to be very helpful to explore their taxonomic identity. In the present compilation, we provide detailed information on estimates of fungi provided by different mycologistsover time. Along with this, a comprehensive analysis of the importance of classical and molecular methods is also presented. In orderto understand the utility of genus and species specific markers in fungal identification, a polyphasic approach to investigate various fungi is also presented in this paper. An account of the study of various fungi based on culture-based and cultureindependent methods is also provided here to understand the development and significance of both approaches. The available information on classical and modern methods compiled in this study revealed that the DNA based molecular studies are still scant, and more studies are required to achieve the accurate estimation of fungi present on earth.

Gymnosporangium species on Malus: species delineation, diversity and host alternation

Gymnosporangium species (Pucciniaceae, Pucciniales, Basidiomycota) are the causal agents of cedar-apple rust diseases, which can lead to significant economic losses to apple cultivars. Currently, the genus contains 17 described species that alternate between spermogonial/aecial stages on Malus species and telial stages on Juniperus or Chamaecyparis species, although these have yet to receive a modern systematic treatment. Furthermore, prior studies have shown that Gymnosporangium does not belong to the Pucciniaceae sensu stricto (s.str.), nor is it allied to any currently defined rust family. In this study we examine the phylogenetic placement of the genus Gymnosporangium. We also delineate interspecific boundaries of the Gymnosporangium species on Malus based on phylogenies inferred from concatenated data of rDNA SSU, ITS and LSU and the holomorphic morphology of the entire life cycle. Based on these results, we propose a new family, Gymnosporangiaceae, to accommodate the genus Gymnosporangium, and recognize 22 Gymnosporangium species parasitic on Malus species, of which G. lachrymiforme, G. shennongjiaense, G. spinulosum, G. tiankengense and G. kanas are new. Typification of G. asiaticum, G. fenzelianum, G. juniperi-virginianae, G. libocedri, G. nelsonii, G. nidus-avis and G. yamadae are proposed to stabilize the use of names. Morphological and molecular data from type materials of 14 Gymnosporangium species are provided. Finally, morphological characteristics, host alternation and geographical distribution data are provided for each Gymnosporangium species on Malus.

Competing sexual-asexual generic names in Agaricomycotina (Basidiomycota) with recommendations for use

With the change to one scientific name for fungal taxa, generic names typified by species with sexual or asexual morph types are being evaluated to determine which names represent the same genus and thus compete for use. In this paper generic names of the Agaricomycotina (Basidiomycota) were evaluated to determine synonymy based on their type. Forty-seven sets of sexually and asexually typified names were determined to be congeneric and recommendations are made for which generic name to use. In most cases the principle of priority is followed. However, 16 generic names are recommended for use that do not have priority and thus need to be protected: Aleurocystis over Matula; Armillaria over Acurtis and Rhizomorpha; Asterophora over Ugola; Botryobasidium over Acladium, Allescheriella, Alysidium, Haplotrichum, Physospora, and Sporocephalium; Coprinellus over Ozonium; Coprinopsis over Rhacophyllus; Dendrocollybia over Sclerostilbum and Tilachlidiopsis; Diacanthodes over Bornetina; Echinoporia over Echinodia; Neolentinus over Digitellus; Postia over Ptychogaster; Riopa over Sporotrichum; Scytinostroma over Artocreas, Michenera, and Stereofomes; Tulasnella over Hormomyces; Typhula over Sclerotium; and Wolfiporia over Gemmularia and Pachyma. Nine species names are proposed for protection: Botryobasidium aureum, B. conspersum, B. croceum, B. simile, Pellicularia lembosporum (syn. B. lembosporum), Phanerochaete chrysosporium, Polyporus metamorphosus (syn. Riopa metamorphosa), Polyporus mylittae (syn. Laccocephalum mylittae), and Polyporus ptychogaster (syn. Postia ptychogaster). Two families are proposed for protection: Psathyrellaceae and Typhulaceae. Three new species names and 30 new combinations are established, and one lectotype is designated.

Inopinatum lactosum gen. & comb. nov., the first yeast-like fungus in Leotiomycetes

Sporobolomyces lactosus is a pink yeast-like fungus that is not congeneric with other members of Sporobolomyces (Basidiomycota, Microbotryomycetes, Sporidiobolales). During our ongoing studies of pink yeasts we determined that S. lactosus was most closely related to Pseudeurotium zonatum (Ascomycota, Leotiomycetes, Thelebolales). A molecular phylogenetic analysis using sequences of the ITS region and the small and large subunit (SSU, LSU) rRNA genes, indicated that four isolates of S. lactosus, including three ex-type isolates, were placed in Thelebolales with maximum support. A new genus is proposed to accommodate S. lactosus, Inopinatum. This is the first pink yeast reported in Leotiomycetes.

A higher-rank classification for rust fungi, with notes on genera

The rust fungi (Pucciniales) with 7000+ species comprise one of the largest orders of Fungi, and one for which taxonomy at all ranks remains problematic. Here we provide a taxonomic framework, based on 16 years of sampling that includes ca. 80 % of accepted genera including type species wherever possible, and three DNA loci used to resolve the deeper nodes of the rust fungus tree of life. Pucciniales are comprised of seven suborders - Araucariomycetineae subord. nov., Melampsorineae, Mikronegeriineae, Raveneliineae subord. nov., Rogerpetersoniineae subord. nov., Skierkineae subord. nov., and Uredinineae - and 18 families - Araucariomycetaceae fam. nov., Coleosporiaceae, Crossopsoraceae fam. nov., Gymnosporangiaceae, Melampsoraceae, Milesinaceae fam. nov., Ochropsoraceae fam. & stat. nov., Phakopsoraceae, Phragmidiaceae, Pileolariaceae, Pucciniaceae, Pucciniastraceae, Raveneliaceae, Rogerpetersoniaceae fam. nov., Skierkaceae fam. & stat. nov., Sphaerophragmiaceae, Tranzscheliaceae fam. & stat. nov., and Zaghouaniaceae. The new genera Araucariomyces (for Aecidium fragiforme and Ae. balansae), Neoolivea (for Olivea tectonae), Rogerpetersonia (for Caeoma torreyae), and Rossmanomyces (for Chrysomyxa monesis, Ch. pryrolae, and Ch. ramischiae) are proposed. Twenty-one new combinations and one new name are introduced for: Angiopsora apoda, Angiopsora chusqueae, Angiopsora paspalicola, Araucariomyces balansae, Araucariomyces fragiformis, Cephalotelium evansii, Cephalotelium neocaledoniense, Cephalotelium xanthophloeae, Ceropsora weirii, Gymnotelium speciosum, Lipocystis acaciae-pennatulae, Neoolivea tectonae, Neophysopella kraunhiae, Phakopsora pipturi, Rogerpetersonia torreyae, Rossmanomyces monesis, Rossmanomyces pryrolae, Rossmanomyces ramischiae, Thekopsora americana, Thekopsora potentillae, Thekopsora pseudoagrimoniae, and Zaghouania notelaeae. Higher ranks are newly defined with consideration of morphology, host range and life cycle. Finally, we discuss the evolutionary and diversification trends within Pucciniales. Citation: Aime MC, McTaggart AR (2020). A higher-rank classification for rust fungi, with notes on genera. Fungal Systematics and Evolution 7: 21-47. doi: 10.3114/fuse.2021.07.02.

Uromyces rebeccae, sp. nov., a newly described rust on the federally endangered plant, California sea-blite (Suaeda californica)

Rust disease was observed on populations of Suaeda californica near Morro Bay, California. The pathogen was identified as a species of Uromyces based on teliospore and urediniospore morphology and nuc 28S rDNA sequence analysis. The isolate was compared with previously described species of Uromyces that infect members of Chenopodiaceae, prompting a taxonomic reevaluation of Uromyces species on Suaeda. Herein, Uromyces rebeccae is described. It can be differentiated from the closely related U. chenopodii (syn.: Aecidium chenopodii-fruticosi; U. giganteus) based on host range, teliospore morphology, and 28S sequence data. The new combination, Uromyces chenopodii-fruticosi, is made for Aecidium chenopodii-fruticosi, the oldest name for Eurasian Suaeda rust. Finally, it was determined that U. giganteus likely does not occur in the United States and that the rust of S. taxifolia in the United States likely comprises a third, yet unnamed taxon, different from both U. rebeccae and U. chenopodii-fruticosi. This is the first record of a rust fungus on S. californica. An identification key for Uromyces species reported on Chenopodiaceae is provided.

Notes, outline and divergence times of Basidiomycota

The Basidiomycota constitutes a major phylum of the kingdom Fungi and is second in species numbers to the Ascomycota. The present work provides an overview of all validly published, currently used basidiomycete genera to date in a single document. An outline of all genera of Basidiomycota is provided, which includes 1928 currently used genera names, with 1263 synonyms, which are distributed in 241 families, 68 orders, 18 classes and four subphyla. We provide brief notes for each accepted genus including information on classification, number of accepted species, type species, life mode, habitat, distribution, and sequence information. Furthermore, three phylogenetic analyses with combined LSU, SSU, 5.8s, rpb1, rpb2, and ef1 datasets for the subphyla Agaricomycotina, Pucciniomycotina and Ustilaginomycotina are conducted, respectively. Divergence time estimates are provided to the family level with 632 species from 62 orders, 168 families and 605 genera. Our study indicates that the divergence times of the subphyla in Basidiomycota are 406–430 Mya, classes are 211–383 Mya, and orders are 99–323 Mya, which are largely consistent with previous studies. In this study, all phylogenetically supported families were dated, with the families of Agaricomycotina diverging from 27–178 Mya, Pucciniomycotina from 85–222 Mya, and Ustilaginomycotina from 79–177 Mya. Divergence times as additional criterion in ranking provide additional evidence to resolve taxonomic problems in the Basidiomycota taxonomic system, and also provide a better understanding of their phylogeny and evolution.

Species identification of European forest pathogens of the genus Milesina (Pucciniales) using urediniospore morphology and molecular barcoding including M.woodwardiana sp. nov

Species of rust fungi of the genus Milesina (Pucciniastraceae, Pucciniales) are distributed mainly in northern temperate regions. They host-alternate between needles of fir (Abies spp.) and fronds of ferns (species of Polypodiales). Milesina species are distinguished based on host taxonomy and urediniospore morphology. In this study, 12 species of Milesina from Europe were revised. Specimens were examined by light and scanning electron microscopy for urediniospore morphology with a focus on visualising germ pores (number, size and position) and echinulation. In addition, barcode loci (ITS, nad6, 28S) were used for species delimitation and for molecular phylogenetic analyses. Barcodes of 72 Milesina specimens were provided, including 11 of the 12 species.

Whereas urediniospore morphology features were sufficient to distinguish all 12 Milesina species except for 2 (M.blechni and M.kriegeriana), ITS sequences separated only 4 of 11 species. Sequencing with 28S and nad6 did not improve species resolution. Phylogenetic analysis, however, revealed four phylogenetic groups within Milesina that also correlate with specific urediniospore characters (germ pore number and position and echinulation). These groups are proposed as new sections within Milesina (sections Milesina, Vogesiacae M. Scholler & Bubner, sect. nov., Scolopendriorum M. Scholler & Bubner, sect. nov. and Carpaticae M. Scholler & Bubner, sect. nov.). In addition, Milesinawoodwardiana Buchheit & M. Scholler, sp. nov. on Woodwardiaradicans, a member of the type section Milesina, is newly described. An identification key for European Milesina species, based on urediniospore features, is provided.

Pest categorisation of Cronartium spp. (non-EU)

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Cronartium spp. (non-EU), a well-defined and distinguishable group of fungal pathogens of the family Cronartiaceae. There are at least 40 species described within the Cronartium genus, of which two are considered native to the EU (C. gentianeum and C. pini) and one has been introduced in the 19th century (C. ribicola) and is now widespread in the EU - these three species are thus not part of this pest categorisation. In addition, the non-EU C. harknessii, C. kurilense and C. sahoanum were already dealt with in a previous pest categorisation. All the non-EU Cronartium species are not known to be present in the EU and are regulated in Council Directive 2000/29/EC (Annex IAI) as harmful organisms whose introduction into the EU is banned. Cronartium spp. are biotrophic obligate plant pathogens. Many of the North American Cronartium species alternate between the aecial host Pinus spp. and telial hosts of various dicotyledonous plants. C. conigenum, C. orientale, C. quercuum and C. strobilinum have different Quercus spp. as their telial hosts. C. orientale and C. quercuum also infect Castanea spp. and Castanopsis spp. The pathogens could enter the EU via host plants for planting and cut flowers and branches. Non-EU Cronartium spp. could establish in the EU, as climatic conditions are favourable to many of them and Pinus and Quercus spp. are common. The pathogens would be able to spread following establishment by movement of host plants, as well as natural spread. Should non-EU Cronartium spp. be introduced in the EU, impacts can be expected on pine, oak and chestnut woodlands, plantations, ornamental trees and nurseries. The Cronartium species present in North America cause important tree diseases. Symptoms on Pinus spp. differ between Cronartium spp., but include galls, cankers, dieback of branches and stems, deformity, tree and cone death. The main knowledge gap concerns the limited available information on (sub)tropical Cronartium spp. The criteria assessed by the Panel for consideration of Cronartium spp. (non-EU) as potential quarantine pests are met, while, for regulated non-quarantine pests, the criterion on the pest presence in the EU is not met.

Pest categorisation of Cronartium harknessii, Cronartium kurilense and Cronartium sahoanum

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Cronartium harknessii, Cronartium kurilense and Cronartium sahoanum, which are well‐defined and distinguishable tree fungal pathogens of the family Cronartiaceae. In 2018, these species were moved from the genus Endocronartium to the genus Cronartium. These pathogens are not known to be present in the EU and are regulated in Council Directive 2000/29/EC (Annex IAI) (as non‐European Endocronartium spp.) as harmful organisms whose introduction into the EU is banned. These three fungi are autoecious rusts completing their life cycle on Pinus spp. C. harknessii is known as the western gall rust or pine‐pine gall rust in North America (Canada, the USA and Mexico). C. kurilense and C. sahoanum are reported from Russia (North Kuril Islands) and Japan. The pathogens could enter the EU via host plants for planting and cut branches. The pathogens could establish in the EU, as climatic conditions are favourable and Pinus spp. are common. The pathogens would be able to spread following establishment by movement of host plants for planting and cut branches, as well as natural spread. Should these pathogens be introduced in the EU, impacts can be expected on pine forests, plantations, ornamental trees and nurseries. The pathogens cause formation of stem galls, which kill young trees and result in stem defect in older trees. The main knowledge gap concerns the limited available information on C. kurilense and C. sahoanum compared to C. harknessii. The criteria assessed by the Panel for consideration of C. harknessii, C. kurilense and C. sahoanum as potential quarantine pests are met, whilst, for regulated non‐quarantine pests, the criterion on the pest presence in the EU is not met.

Microbial enrichment and gene functional categories revealed on the walls of a spent fuel pool of a nuclear power plant

Microorganisms developing in the liner of the spent fuel pool (SFP) and the fuel transfer channel (FTC) of a Nuclear Power Plant (NPP) can form high radiation resistant biofilms and cause corrosion. Due to difficulties and limitations to obtain large samples from SFP and FTC, cotton swabs were used to collect the biofilm from the wall of these installations. Molecular characterization was performed using massively parallel sequencing to obtain a taxonomic and functional gene classification. Also, samples from the drainage system were evaluated because microorganisms may travel over the 12-meter column of the pool water of the Brazilian Nuclear Power Plant (Angra1), which has been functioning since 1985. Regardless of the treatment of the pool water, our data reveal the unexpected presence of Fungi (Basidiomycota and Ascomycota) as the main contaminators of the SFP and FTC. Ustilaginomycetes (Basidiomycota) was the major class contributor (70%) in the SFP and FTC reflecting the little diversity in these sites; nevertheless, Proteobacteria, Actinobacteria, Firmicutes (Bacilli) were present in small proportions. Mapping total reads against six fungal reference genomes indicate that there is, in fact, a high abundance of fungal sequences in samples collected from SFP and FTC. Analysis of the ribosomal internal transcribed spacer (ITS) 1 and 2 regions and the protein found in the mitochondria of eukaryotic cells, cytochrome b (cytb) grouped our sample fungi in the clade 7 as Ustilago and Pseudozyma. In contrast, in the drainage system, Alphaproteobacteria were present in high abundances (55%). The presence of Sphingopyxis, Mesorhizobium, Erythrobacter, Sphingomonas, Novosphingobium, Sphingobium, Chelativorans, Oceanicaulis, Acidovorax, and Cyanobacteria was observed. Based on genomic annotation data, the assessment of the biological function found a higher proportion of protein-coding sequences related to respiration and protein metabolism in SFP and FTC samples. The knowledge of this biological inventory present in the system may contribute to further studies of potential microorganisms that might be useful for bioremediation of nuclear waste.

Classiculasinensis, a new species of basidiomycetous aquatic hyphomycetes from southwest China

Classiculasinensis, isolated from decaying leaves from Mozigou, Chongqing Municipality, China, is described as a new species. The new species is a member of basidiomycetous aquatic hyphomycetes which represent a small proportion of all aquatic hyphomycetes. This species falls within the genus Classicula (Classiculaceae, Pucciniomycotina) and is closely related to C.fluitans, based on multiple gene sequence analyses. Morphologically, it is characterised by the apical, hyaline, obclavate or navicular conidia with several hair-like lateral appendages and by its holoblastic and monoblastic conidiogenesis, with a flat un-thickened conidiogenous locus. Clamp connections and haustorial branches were often observed in culture.

The species of Coleosporium (Pucciniales) on Solidago in North America

Species of Coleosporium (Pucciniales) are rust fungi that typically alternate between pines and angiosperms. In North America, species of Coleosporium often infect Solidago (goldenrods), although their taxonomy on these hosts is unresolved. Joseph. C. Arthur and George B. Cummins regarded these as a single species, Coleosporium solidaginis (fide Arthur) or C. asterum (fide Cummins), but later inoculation studies demonstrated the presence of more than one species, distinguishable by their aecial hosts. A more recent taxonomic study of Coleosporium found that specimens on Solidago identified as C. asterum in North America were not conspecific with the type, which is from Japan, prompting the present study. Herein, we conducted a systematic study on ca. 60 collections of Coleosporium infecting species of Asteraceae from North America using regions of ribosomal DNA and morphology of teliospores and basidia. Our data indicate at least three species of Coleosporium occur on Solidago in North America, C. solidaginis, C. montanum comb. nov., which is proposed for the taxon that has commonly been identified as C. asterum in North America, and C. delicatulum, all of which can be differentiated by morphology of their basidia. In addition, the challenges of marker selection for molecular barcoding of rust fungi is discussed.