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Parsimony tree from the analysis of nuclear ribosomal internal transcribed spacer (ITS) region sequence data of Puccinia coronata . Phylogenetic analysis resulted in three optimal trees, each with a tree length of 185 steps (CI = 0.9081, HI = 0.0919, RI = 0.9424, and RC = 0.8518), one of which is shown. Numbers above or below branches indicate percentage of congruent clusters in 1000 bootstrap trials, and only values above 80% are shown. Clades are indicated along the right-hand side . Two DNA sequences of P. graminis (AY114289, DQ355455) were used as an outgroup
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Species of macrocyclic, heteroecious grass rusts often have been defined with wide host ranges and variation in spore morphology.
Consequently, some are species complexes and contain genetically distinct forms. Molecular analyses, together with morphological
and biological methods, provide powerful means to dissect these complexes. Puccinia coronat...
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Context 1
... bp was sequenced for each sample including the 3 ′ -end of the nuclear ribosomal, the complete ITS region (ITS1, 5.8S, and ITS2), and the 5 -end of the 28S providing an aligned sequence of 1308 characters. Variation in the 5 ′ -end of the 28S was low and therefore not included in the phylogenetic analysis. Of the 649 aligned characters analyzed, 508 were constant, 34 were variable but uninfor- mative, and 107 characters were parsimony-informative. Parsimony analysis of ITS sequence data from 15 collections resulted in three optimal trees, each with a tree length of 185 steps, one of which is shown in Fig. 1. Only minor variation of the terminal structure occurred between the three trees. DNA sequences from 15 collections of P. coronata grouped into six well-supported clades with bootstrap values of 88% or greater. Clade I consisted of DNA sequences from one collection of Rhamnus catharticus (aecial host, HSZ1309) and two collections of Elytrigia repens (73MN873 and MN01), collected from the United States. All three sequences were nearly identical. Clade II consisted of one collection from R. saxatilis (aecial, PRC 247) and two from Bromus erectus (telial, PRC 194, PRC 196), collected from the Czech Republic and Slovakia. All three sequences were identical. Clade III consisted of two collections from R. catharticus (aecial host, HSZ0757 and HSZ0760) and two from Bromus inermis (telial host, HSZ1400 and HSZ1401), collected from the United States. Clades II and III are closely related and formed a well-supported branch with 85% bootstrap value. Clade IV consisted of one collection from Arrhenatherum elatius (telial host, PRC 190) and one from Holcus lanatus (telial host, PRC 200) collected from the Czech Republic and Ireland, respectively. The two sequences were nearly identical. Clade V consisted of collections from R. catharticus (aecial host, HSZ0761), Avena sativa (telial host, 93MN437), and Lolium perenne (telial host, PRC 203) collected from the United States and the Czech Republic. All three sequences were nearly identical. Clades IV and V are closely related and formed a well- supported branch (95% bootstrap). Clade VI consisted of the partial ITS sequence of P. coronata collected from the telial host Calamagrostis canadensis used in the analysis by Zambino and Szabo (1993). Approximately 1250 bp was sequenced for each collection, including the 3 ′ -end of the nuclear ribosomal, the complete ITS region (ITS1, 5.8S, and ITS2), and the 5 ′ -end of the 28S. Variation in the 5 ′ -end of the 28S was low, and therefore these data were not included in the phylogenetic analysis. Of the 700 aligned characters analyzed, 507 were constant, 74 were variable but parsimony-uninformative, and 119 characters were informative. Parsimony analysis of the ITS sequence data from 15 collections resulted in four optimal trees, each with a tree length of 288 steps, one of which is shown in Fig. 2. Only minor variation on the terminal structure occurred among the four trees. DNA sequences from 15 P. andropogonis collections grouped into five well-supported clades with bootstrap values of 99% or greater. All collections were made from the United States in two states (Minnesota and Wisconsin). Clade I consisted of one collection from Penstemon gracilis (aecial host, Scrophulariacea, HSZ0262) and two collections from Schizachyrium scoparis (telial host, HSZ0217 and HSZ0225). All three sequences were similar but showed variation between the collections, with the P. gracilis sequence being the most different. Each of the collections was from a different site. Clade II consisted of two collections from Castilleja coccinea (aecial host, Scrophulariacea, HSZ0389 and HSZ0388) and one collection from S. scoparis (telial host, HSZ0562). The three collections were from a single site (Afton, Minnesota, USA), the only site in which C. coccinea was found infected with P. andropogonis. All three sequences were nearly identical. Clade III consisted of one collection from Comandra umbellata (aecial host, Santalaceae, HSZ0263) and two collections from Andropogon gerardii (telial host, HSZ0224 sand HSZ0237). All three sequences were nearly identical. Clade IV consisted of one collection from Zanthoxylum americanum (aecial host, Rutaceae, HSZ0265) and two collections from A. gerardii (telial host, HSZ0574 and HSZ0576). All three sequences were nearly identical. The three collections came from the same site (Fish Lake, WI, USA). Eight of the 15 collections came from this site and are grouped into four of the five clades. Clade V consisted of one collection from Lupinus perennis (aecial host, Fabaceae, HSZ0264) and two collections from A. gerardii (telial host, HSZ0027 and HSZ0219). The three collections came from the same site (Fish Lake, WI, USA). All three sequences were nearly identical. Phylogenetic analysis of the complete ITS region clearly demonstrated that P. coronata is a species complex consist- ing of at least six distinct clades (see Fig. 1). This result confirms the analysis by Zambino and Szabo (1993), which separated P. coronata into three distinct groups composed of collections from Calamagrostis canadensis (clade VI), Elytrigia repens ( = Agropyron repens , clade I), and Avena sativa and Lolium perenne (clade V). The latter group was previously shown to also include collections from Alopecurus aequalis and Festuca elatior . The three new groups consist of collections from the telial hosts Holcus lanatus and Arrhenatherum elatius (clade IV), Bromus erectus (clade II), and Bromus inermis (clade III). Four of the six clades also contain collections from Rhamnus aecial hosts, providing the first molecular confirmation of the link- age between telial and aecial hosts. Recently, collections of P. coronata from B. inermis (clade III) were described and shown to be distinct from other formae speciales and varieties based primarily on host range, teliospore morphology, and being self-fertile (Delgado et al. 2001; Anikster et al. 2003). This new morphotype was provisionally designated P. coronata f. sp. bromi sensu Mühlethaler by Delgado et al. (2001) and has only been found in North America. In Europe, crown rust ( P. coronata var. coronata ) has been described on several species of brome grass, including B. erectus, B. inermis , and B. ramosus (Urban and Marková 1994). The genetic connection between aecia on R. cathartica and uredinia/telia on B. erectus and B. inermis has been demonstrated (reviewed by Urban and Marková 1994). Two European collections of P. coronata from B. erectus formed a distinct but closely related clade (II) to P. coronata f. sp. bromi sensu Mühlethaler from B. inermis (clade III). The teliospores of the collections from B. erectus have shorter apical pro- jections (Y. Anikster, personal communication) than P. coronata f. sp. bromi . The molecular results presented here combined with morphological data suggest that the crown rust on Bromus is a separate species ( P. coronata species 1, PcSP1) and should be subdivide into at least two subspecies. Molecular and host range studies indicate that R. cathartica and R. saxatilis are aecial hosts of PcSP1. Fraser and Ledingham (1933) described crown rust ( P. coronata var. bromi ) of brome grass from Canada. Host range studies demonstrated that the aecial host was Lepargyraea canadensis rather than R. cathartica , and telial hosts did not include B. inermis . At present it is not clear what the relationship is between P. coronata var. bromi sensu Fraser and Ledingham and the two brome rusts, P. coronata var. coronata and P. coronata f. sp. bromi sensu Mühlethaler, examined in this study. Molecular and morphological studies are needed to clarify this issue. As previously described, molecular analysis placed collections of P. coronata from A. sativa and L. perenne in a distinct group (Zambino and Szabo 1993), which is con- firmed by these results (clade V). Based on morphological characters and host range, crown rust on A. sativa was classified as P. coronata var. avenae by Cummins (1971) and Urban and Marková (1994). Anikster et al. (2003) compared morphological and biological characteristics of P. coronata var. avenae and P. coronata f. sp. bromi sensu Mühlethaler and showed that these two crown rusts were distinctly different; characters included teliospore size, teliospore morphology, pycniospore DNA content, promycelium morphology, and substomatal vesicle morphology. In addition to L. perenne , DNA sequence analysis indicated that crown rust on A. aequalis and F. elatior be included with P. coronata var. avenae (Zambino and Szabo 1993). In contrast to the molecular data, crown rust on L. perenne , A. aequalis , and F. elatior were included in P. coronata var. coronata rather than in P. coronata var. avenae (Urban and Marková 1994). This classification is based primarily on differences in urediniospore morphology. P. coronata samples collected from the telial hosts Arrhenatherum elatius and Holcus lanatus formed a well- supported clade (IV) that is closely related to clade V. This molecular result is supported by taxonomic classification of Urban and Marková (1994). P. coronata var. avenae is subdivided into P. coronata var. avenae f. sp. avenae and P. coronata var. avenae f. sp. graminicola . The latter includes telial hosts A. elatius and H. lanatus . Based on the genetic similarities between these rust collections (clades IV and V) and the genetic distance between the clades IV/V and the other clades, P. coronata var. avenae should be considered a separate species, PcSP2. This new species would include crown rust on A. aequalis , A. elatius , A. sativa , F. elatior , H. lanatus , and L . perenne . PcSP2 should be divided into at least two subgroups corresponding to clades IV and V. Additional morphological studies are needed to verify the molecular data. Schwinghamer (1955) described a new morphotype of P. coronata collected from E. repens ( = Agropyron repens ) ...
Context 2
... sequences were initially aligned using the program Clustal W (Thompson et al. 1994) and then hand edited using the multiple sequence editor in MacVector (version 7.2.3; Accelrys, San Diego, CA, USA). Phylogenetic analysis of the data sets included the complete ITS1, 5.8S, and ITS2 region ( P. andropogonis, 700 characters, 1–719 minus 191–194 and 235–249; P. coronata , 649 characters) using an heuristic parsimony program (PAUP version 4.04b10; Swofford 2001) with random stepwise addition option with 10 replicas. Support for the nodes of the trees was deter- mined by analysis of 1000 bootstrap replicas. DNA sequence alignments and trees have been submitted to TreeBASE. Approximately 1250 bp was sequenced for each sample including the 3 ′ -end of the nuclear ribosomal, the complete ITS region (ITS1, 5.8S, and ITS2), and the 5 -end of the 28S providing an aligned sequence of 1308 characters. Variation in the 5 ′ -end of the 28S was low and therefore not included in the phylogenetic analysis. Of the 649 aligned characters analyzed, 508 were constant, 34 were variable but uninfor- mative, and 107 characters were parsimony-informative. Parsimony analysis of ITS sequence data from 15 collections resulted in three optimal trees, each with a tree length of 185 steps, one of which is shown in Fig. 1. Only minor variation of the terminal structure occurred between the three trees. DNA sequences from 15 collections of P. coronata grouped into six well-supported clades with bootstrap values of 88% or greater. Clade I consisted of DNA sequences from one collection of Rhamnus catharticus (aecial host, HSZ1309) and two collections of Elytrigia repens (73MN873 and MN01), collected from the United States. All three sequences were nearly identical. Clade II consisted of one collection from R. saxatilis (aecial, PRC 247) and two from Bromus erectus (telial, PRC 194, PRC 196), collected from the Czech Republic and Slovakia. All three sequences were identical. Clade III consisted of two collections from R. catharticus (aecial host, HSZ0757 and HSZ0760) and two from Bromus inermis (telial host, HSZ1400 and HSZ1401), collected from the United States. Clades II and III are closely related and formed a well-supported branch with 85% bootstrap value. Clade IV consisted of one collection from Arrhenatherum elatius (telial host, PRC 190) and one from Holcus lanatus (telial host, PRC 200) collected from the Czech Republic and Ireland, respectively. The two sequences were nearly identical. Clade V consisted of collections from R. catharticus (aecial host, HSZ0761), Avena sativa (telial host, 93MN437), and Lolium perenne (telial host, PRC 203) collected from the United States and the Czech Republic. All three sequences were nearly identical. Clades IV and V are closely related and formed a well- supported branch (95% bootstrap). Clade VI consisted of the partial ITS sequence of P. coronata collected from the telial host Calamagrostis canadensis used in the analysis by Zambino and Szabo (1993). Approximately 1250 bp was sequenced for each collection, including the 3 ′ -end of the nuclear ribosomal, the complete ITS region (ITS1, 5.8S, and ITS2), and the 5 ′ -end of the 28S. Variation in the 5 ′ -end of the 28S was low, and therefore these data were not included in the phylogenetic analysis. Of the 700 aligned characters analyzed, 507 were constant, 74 were variable but parsimony-uninformative, and 119 characters were informative. Parsimony analysis of the ITS sequence data from 15 collections resulted in four optimal trees, each with a tree length of 288 steps, one of which is shown in Fig. 2. Only minor variation on the terminal structure occurred among the four trees. DNA sequences from 15 P. andropogonis collections grouped into five well-supported clades with bootstrap values of 99% or greater. All collections were made from the United States in two states (Minnesota and Wisconsin). Clade I consisted of one collection from Penstemon gracilis (aecial host, Scrophulariacea, HSZ0262) and two collections from Schizachyrium scoparis (telial host, HSZ0217 and HSZ0225). All three sequences were similar but showed variation between the collections, with the P. gracilis sequence being the most different. Each of the collections was from a different site. Clade II consisted of two collections from Castilleja coccinea (aecial host, Scrophulariacea, HSZ0389 and HSZ0388) and one collection from S. scoparis (telial host, HSZ0562). The three collections were from a single site (Afton, Minnesota, USA), the only site in which C. coccinea was found infected with P. andropogonis. All three sequences were nearly identical. Clade III consisted of one collection from Comandra umbellata (aecial host, Santalaceae, HSZ0263) and two collections from Andropogon gerardii (telial host, HSZ0224 sand HSZ0237). All three sequences were nearly identical. Clade IV consisted of one collection from Zanthoxylum americanum (aecial host, Rutaceae, HSZ0265) and two collections from A. gerardii (telial host, HSZ0574 and HSZ0576). All three sequences were nearly identical. The three collections came from the same site (Fish Lake, WI, USA). Eight of the 15 collections came from this site and are grouped into four of the five clades. Clade V consisted of one collection from Lupinus perennis (aecial host, Fabaceae, HSZ0264) and two collections from A. gerardii (telial host, HSZ0027 and HSZ0219). The three collections came from the same site (Fish Lake, WI, USA). All three sequences were nearly identical. Phylogenetic analysis of the complete ITS region clearly demonstrated that P. coronata is a species complex consist- ing of at least six distinct clades (see Fig. 1). This result confirms the analysis by Zambino and Szabo (1993), which separated P. coronata into three distinct groups composed of collections from Calamagrostis canadensis (clade VI), Elytrigia repens ( = Agropyron repens , clade I), and Avena sativa and Lolium perenne (clade V). The latter group was previously shown to also include collections from Alopecurus aequalis and Festuca elatior . The three new groups consist of collections from the telial hosts Holcus lanatus and Arrhenatherum elatius (clade IV), Bromus erectus (clade II), and Bromus inermis (clade III). Four of the six clades ...
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... Rust fungi are wind-dispersed obligate biotrophic pathogens, typically heteroecious and host-specific on their grass (telial) host 55 . The aecial host of P. andropogonis is bastard toadflax (Comandra umbellata) 38,54 . Disease severity on big bluestem increases with proximity to bastard toadflax due to dispersal of aeciospores, although this effect fades beyond 40 m 37 . ...
Plant disease often increases with N, decreases with CO2, and increases as biodiversity is lost (i.e., the dilution effect). Additionally, all these factors can indirectly alter disease by changing host biomass and hence density-dependent disease transmission. Yet over long periods of time as communities undergo compositional changes, these biomass-mediated pathways might fade, intensify, or even reverse in direction. Using a field experiment that has manipulated N, CO2, and species richness for over 20 years, we compared severity of a specialist rust fungus (Puccinia andropogonis) on its grass host (Andropogon gerardii) shortly after the experiment began (1999) and twenty years later (2019). Between these two sampling periods, two decades apart, we found that disease severity consistently increased with N and decreased with CO2. However, the relationship between diversity and disease reversed from a dilution effect in 1999 (more severe disease in monocultures) to an amplification effect in 2019 (more severe disease in mixtures). The best explanation for this reversal centered on host density (i.e., aboveground biomass), which was initially highest in monoculture, but became highest in mixtures two decades later. Thus, the diversity-disease pattern reversed, but disease consistently increased with host biomass. These results highlight the consistency of N and CO2 as drivers of plant disease in the Anthropocene and emphasize the critical role of host biomass—despite potentially variable effects of diversity—for relationships between biodiversity and disease.
... For each of the four single pustule isolates (Table 1), consensus sequences generated for the ITS, COI, RPB2, and b-tubulin loci were used for phylogenetic analysis. Original sequences and selected sequences from Kenaley et al. (2017), Liu and Hambleton (2013), and Szabo (2006) were aligned with MAFFT v7.450 and edited in Geneious. In MEGA v. 7.0.26 ...
... Trees were reformatted in FigTree v1.4.4 (Rambaut 2009) and Microsoft PowerPoint. Other samples were identified with a local BLASTn search (Zhang et al. 2000) using a library containing all sequences from Kenaley et al. (2017), Liu and Hambleton (2013), Szabo (2006), and from the four isolates identified by phylogenetic analysis. ...
Puccinia coronata var. coronata (Pcc) causes crown rust disease of glossy buckthorn (Frangula alnus) and reed canarygrass (Phalaris arundinacea), two highly invasive plant species in North America. Pcc is closely related to major pathogens of cereals, turfgrasses, and forage grasses. It occurs throughout Europe but was first recorded in North America in 2013. Where its hosts co-occur, such as in wetlands in the Twin Cities metro area in Minnesota, we have observed Pcc causing significant infection that results in defoliation and fruit loss in glossy buckthorns and premature leaf senescence in reed canarygrass. In this research, we mapped the distribution of this likely recently introduced rust fungus and provide a description of disease signs and symptoms and pathogen morphology. Samples were acquired by two primary means: by surveys in Minnesota and by correspondence with users of iNaturalist.org, a social network for nature enthusiasts and community scientists. With an Oxford Nanopore MinION, we sequenced two to four loci from twenty-two samples across thirteen states and identified samples by phylogenetic analysis and sequence similarity. Notably, four pure isolates appear to have intragenomic variation of the ITS region. We find that Pcc is present throughout the range of glossy buckthorn in the eastern United States. In Minnesota, Pcc is not common outside the range of glossy buckthorn, however, despite the presence of susceptible grass hosts.
... Herpotrichiellaceae, with many documented decomposers of plants or fungi (Untereiner and Malloch, 1999). Among indicators that were significant prior to FDR correction were Puccinia andropogonis, a common rust pathogen of the dominant grasses in the Great Plains (Szabo, 2006) and Phyllozyma linderae (basionym Sporobolomyces linderae Nakase, M. Takash. & Hamam.), a basidiomycetous phyllosphere yeast in the Phylum Pucciniomycotina, whose ecology remains elusive (Wang et al., 2015). ...
Plant communities and fungi inhabiting their phyllospheres change along precipitation gradients and often respond to changes in land use. Many studies have focused on the changes in foliar fungal communities on specific plant species, however, few have addressed the association between whole plant communities and their phyllosphere fungi. We sampled plant communities and associated phyllosphere fungal communities in native prairie remnants and post-agricultural sites across the steep precipitation gradient in the central plains in Kansas, USA. Plant community cover data and MiSeq ITS2 metabarcode data of the phyllosphere fungal communities indicated that both plant and fungal community composition respond strongly to mean annual precipitation (MAP), but less so to land use (native prairie remnants vs. post-agricultural sites). However, plant and fungal diversity were greater in the native remnant prairies than in post-agricultural sites. Overall, both plant and fungal diversity increased with MAP and the communities in the arid and mesic parts of the gradient were distinct. Analyses of the linkages between plant and fungal communities (Mantel and Procrustes tests) identified strong correlations between the composition of the two. However, despite the strong correlations, regression models with plant richness, diversity, or composition (ordination axis scores) and land use as explanatory variables for fungal diversity and evenness did not improve the models compared to those with precipitation and land use (ΔAIC < 2), even though the explanatory power of some plant variables was greater than that of MAP as measured by R2. Indicator taxon analyses suggest that grass species are the primary taxa that differ in the plant communities. Similar analyses of the phyllosphere fungi indicated that many plant pathogens are disproportionately abundant either in the arid or mesic environments. Although decoupling the drivers of fungal communities and their composition – whether abiotic or host-dependent – remains a challenge, our study highlights the distinct community responses to precipitation and the tight tracking of the plant communities by their associated fungal symbionts.
... Although it has been used for species delimitation of some groups (Weber et al. 2002;Szabo 2006;Chatasiri et al. 2006;Alaei et al. 2009), the ITS region is not an effective barcode for rust fungi; intra-specific and intra-individual variation are observed in a wide range of taxa potentially misleading identification, but it is also difficult to amplify without rustspecific primers and the presence of indels inhibits direct sequencing (McTaggart and Aime 2018). The LSU has been used as an alternative barcode for rust fungi instead, alone or with other markers (e.g., Bennett et al. 2011;McTaggart et al. 2015a;Maier et al. 2016;Ebinghaus et al. 2018). ...
Species delimitation is one of the most fundamental processes in biology. Biodiversity undertakings, for instance, require explicit species concepts and criteria for species delimitation in order to be relevant and translatable. However, a perfect species concept does not exist for Fungi. Here, we review the species concepts commonly used in Basidiomycota, the second largest phylum of Fungi that contains some of the best known species of mushrooms, rusts, smuts, and jelly fungi. In general, best practice is to delimitate species, publish new taxa, and conduct taxonomic revisions based on as many independent lines of evidence as possible, that is, by applying a so-called unifying (or integrative) conceptual framework. However, the types of data used vary considerably from group to group. For this reason we discuss the different classes of Basidiomycota, and for each provide: (i) a general introduction with difficulties faced in species recognition, (ii) species concepts and methods for species delimitation, and (iii) community recommendations and conclusions.
... Po raz pierwszy opisana została przez Cordę w 1837 r. [Liu i Hambleton 2013]. Według Szabo [2006] P. coronata jest kompleksem gatunkowym obejmującym wiele linii filogenetycznych. Na podstawie badań Liu i Hambleton [2013] uwzględniających morfologię, właściwości molekularne, zasięg telialnego żywiciela i rozmieszczenie geograficzne, rozpoznano siedem taksonów, m.in. ...
... Po raz pierwszy opisana została przez Cordę w 1837 r. [Liu i Hambleton 2013]. Według Szabo [2006] P. coronata jest kompleksem gatunkowym obejmującym wiele linii filogenetycznych. Na podstawie badań Liu i Hambleton [2013] uwzględniających morfologię, właściwości molekularne, zasięg telialnego żywiciela i rozmieszczenie geograficzne, rozpoznano siedem taksonów, m.in. ...
... Modern molecular phylogenetics has reshaped our understanding of the realized host range of many pathogens. Many pathogens with a similar morphology and which were once thought to be generalists on a wide range of host species have been shown to be species complexes, composed of multiple cryptic species each specialized to a small number of hosts (Szabo 2006;Le Gac et al. 2007;Malenke et al. 2009;Rouxel et al. 2013;Vialle et al. 2013). However, phylogenetic methods alone may be insufficient for determining a pathogen's potential host range if sampling of host diversity is limited. ...
Determining the processes that drive the evolution of pathogen host range can inform our understanding of disease dynamics and the potential for host‐shifts. In natural populations, patterns of host range could be driven by genetically based differences in pathogen infectivity or ecological differences in host availability. In northwestern Italy, four reproductively isolated lineages of the fungal plant‐pathogen Microbotryum have been shown to co‐occur on several species in the genus Dianthus. We carried out cross‐inoculation experiments to determine whether patterns of realized host range in these four lineages were driven by differences in infectivity and to test whether there was evidence of a trade‐off between host range and within‐host reproduction. We found strong concordance between field patterns of host range and pathogen infectivity on different Dianthus species using experimental inoculation, indicating that infection ability is a major driving force of host range. However, we found no evidence of a trade‐off between the ability to infect a wider range of host species and spore production on a shared host.
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... The adoption of molecular-based phylogenetic approaches, in lieu of or integrated with morphologic comparisons, over the last two decades has led to the increasing discovery of cryptic rust fungi, indicating that phenotypic similarities can be due to morphological convergence rather than genetic inheritance from a shared ancestor (synapomorphies). Thus, morphological-based classification can be misinformative for inference(s) of evolutionary relationships and delimiting species (Roy et al. 1998;Szabo 2006;van der Merwe et al. 2007;Maier et al. 2003;Hambleton 2010, 2013;Bennett et al. 2011;Yun et al. 2011;Kenaley et al. 2014;Vialle et al. 2013;Hambleton 2010, 2013). This is exemplified by the genus Uromyces, whereby numerous taxa within the genus have long been considered one-celled, teliospore variants of the Puccinia spp. ...
... The absence of flowering spurge within the P. emaculata and P. novopanici groups confirms that E. corollata is not an alternate host to P. emaculata nor P. novopanici, as proposed by Demers et al. 2017. Considering the close phylogenetic relationship between P. emaculata and P. novopanici as well as the influence of aecial hosts on the evolutionary trajectory of rust fungi (Aime 2006;Szabo 2006;van der Merwe et al. 2008;Alaei et al. 2009;Liu and Hambleton 2013;Vialle et al. 2013;Aime et al. 2018), these species likely share an ancestral or extant related aecial host. Thus, elucidating the aecial host for either P. emaculata or P. novopanici could provide a definite starting point for identifying the aecial host(s) for the other. ...
... Of the three rust fungi identified on bioenergy cultivars of switchgrass, only P. pammelii has the characteristic heteroecious, macrocyclic life cycle commonly associated with rust fungi in tall prairie ecosystems (Szabo 2006). Herein, as also reported by Demers et al. (2017), P. pammelii was resolved to a well-supported monophyletic group (clade III), consisting of one isolate (PUC-24) and the aecial state, Aecidium pammelii, on Euphorbia corollata (Figs. 1 and 4). ...
Research was undertaken to clarify the taxonomic identity of leaf rust (Pucciniales) fungi on bioenergy switchgrass in the Eastern and Central U.S. We integrated internal transcribed spacer 2 (ITS2) and partial 28S ribosomal RNA gene sequence data from collections taken from cultivated switchgrass and herbarium specimens, including purported aecial and telial states of Puccinia graminicola and Puccinia pammelii. Maximum likelihood and Bayesian analyses revealed four monophyletic clades: Puccinia emaculata sensu stricto (s.s.), P. pammelii, P. graminicola, and Puccinia novopanici. Results also indicated that P. emaculata s.s. was not affecting cultivated, bioenergy switchgrass. Aecidium pammelii and P. pammelii were distinct phylogenetically from P. emaculata s.s. and grouped within a well-supported clade, demonstrating aecial-telial host alternation for P. pammelii between Euphorbia corollata and switchgrass. Aecidium stillingiae on queen’s delight (Stillingia sylvatica)—a purported aecial state host for P. graminicola—shared identical sequences with the recently described species Puccinia pascua. The latter fungus, however, was recovered within a subclade of P. graminicola. Hence, queen’s delight likely is not an aecial host to P. graminicola s.s. Additional molecular studies are warranted to determine species boundaries within the P. graminicola complex. The majority of contemporary collections from cultivated switchgrass were recognized as P. novopanici. Collectively, bioenergy switchgrass is host to at least three phylogenetically distinct species, presenting a significant challenge to the future selection and breeding of switchgrass with improved rust resistance.
... S3, S4) confirm that the signs of fungal infections on J. formosana and S. randaiensis belong to G. corniforme. This evidence of host alternation is analogous to the studies of heteroecious rusts in the genera Gymnosporangium (Cao et al., 2017;Zhao et al., 2016), Puccinia (Shen, Huang, Chung, & Hung, 2017;Szabo, 2006), Phakopsora (Chatasiri & Ono, 2008), and Uromyces (Pfunder, Schürch, & Roy, 2001). The method used to obtain sequences covering the SSU rDNA, ITS, and LSU rDNA regions is not only applicable to Puccinia species (Shen et al., 2016a(Shen et al., , 2017 but also works well for Gymnosporangium species. ...
Three rust fungi from high mountains and pear-producing areas in Taiwan were described using morphological and molecular data based on 34 specimens. Gymnosporangium corniforme was demonstrated to produce spermogonia and aecia on Sorbus randaiensis based on molecular analyses and inoculation experiments. The pear rust pathogen G. unicorne was discovered in Taiwan for the first time. Gymnosporangium niitakayamense sp. nov. was observed on the leaves of Photinia niitakayamensis. It was distinct from other species in peridial cell wall structures, i.e., smooth outer wall, rugose side wall, and coralloid projections on the inner wall, and in having echinulate aeciospores.
... Nonetheless, some of these designations remain in use to indicate the major grass hosts, as in the case of Pca. Most recently, the implementation of molecular analysis has shown that P. coronata encompasses multiple species (Szabo, 2006) and suggests the division of the complex into seven species (Liu and Hambleton, 2013). For the purpose of this review, we refer to Pca as a pathogen affecting primarily cultivated and wild oat, as well as some grasses, such as Lolium, and which, in previous publications, has been denominated as P. coronata var. ...
... avenae (Liu and Hambleton, 2013) or P. coronata var. avenae, PcSP2 (Szabo, 2006). In this review, we summarize the current knowledge on this pathogen, including the economic importance and life cycle, as well as perspectives on rust virulence, disease management and future research directions. ...
Control:
Most crown rust management strategies involve the use of rust-resistant crop varieties and the application of fungicides. The attainment of the durability of resistance against Pca is difficult as it is a highly variable pathogen with a great propensity to overcome the genetic resistance of varieties. Thus, adult plant resistance is often exploited in oat breeding programmes to develop new crown rust-resistant varieties. Useful website: https://www.ars.usda.gov/midwest-area/st-paul-mn/cereal-disease-lab/docs/cereal-rusts/race-surveys/.
