| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Centro de Recursos Microbiológicos (CREM), Secção Autónoma de Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
Correspondence
Álvaro Fonseca
amrf{at}fct.unl.pt
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
Published online ahead of print on 9 August 2002 as DOI 10.1099/ijs.0.02437-0.
The GenBank accession numbers of sequences determined in this study are AF492024–AF492075 (D1/D2) and AF492076–AF492129 and AF494056 (ITS).
A dendrogram resulting from analysis of combined MSP-PCR banding patterns is available as supplementary material in IJSEM Online (http://ijs.sgmjournals.org).
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
to accommodate a heterogeneous assemblage of basal lineages of the phylum Ascomycota (for a discussion of the taxa in these lineages see: Alexopoulos et al., 1996; Kurtzman & Sugiyama, 2001). More recently, Eriksson & Winka (1997) have formally proposed the subphylum Taphrinomycotina for the archiascomycete lineages. The classical systematic studies of the genus Taphrina were carried out from the late 1800s through to the 1940s (Mix, 1936) and culminated in the monograph published by Mix (1949, 1954). No other comprehensive studies have been published since then, although some work has involved biochemical characterization of the few species that have been maintained in pure culture (reviewed by Kramer, 1987; Moore, 1998) and some authors have reported on regional surveys of the genus (e.g. Gjaerum, 1964; Bacigálová, 1997). More recently, molecular methods (namely sequencing of the 18S rRNA gene) have been used to unveil phylogenetic relationships among Taphrina species and other members of the archiascomycetes, but this study involved only a limited number of species represented by single strains (Sjamsuridzal et al., 1997).
All Taphrina species are dimorphic (Mix, 1949; Kramer, 1987). Their filamentous states are parasitic on vascular plants belonging to different families, where they cause diverse malformations of the infected tissue such as leaf curl, leaf blisters or spots, galls on stems or inflorescences and witches' brooms (Mix, 1949). Economically important hosts include some fruit trees, namely Prunus spp. (peach, plum, cherry). The best known species is Taphrina deformans (Berk.) Tulasne, the agent of peach leaf curl, a disease that affects orchards throughout the temperate regions of the world (Mix, 1935). Mycelium and the distinctive naked asci of Taphrina species are formed exclusively in their parasitic phase, whereas the yeast states, which result from budding of the ascospores, are saprobic and can be grown on artificial media (Mix, 1949; Kramer, 1987). The existing cultures correspond to yeast forms that were, in most cases, isolated from infected plant material using the spore-fall method. Differentiation from conventional yeasts can be accomplished by a unique combination of physiological and biochemical characteristics displayed by Taphrina yeast phases: a negative Diazonium blue B reaction; positive results in tests for the presence of urease and extracellular amyloid compounds; and cell-wall carbohydrate composition (Prillinger et al., 1990). However, there has been some confusion in the literature dealing with Taphrina due to the inadvertent study of strains of ascomycetous or basidiomycetous yeasts misidentified as Taphrina species (e.g. Heath et al., 1982; Sjamsuridzal et al., 1997; Moore, 1998).
Taphrina species have been differentiated mainly on the basis of host range, geographical distribution, type and site of infection, localization of the mycelium and morphology of sexual structures in the infected tissue (Mix, 1949). However, the validity of separating species on related hosts has been debated by several authors (Mix, 1949; Gjaerum, 1964). Molecular methods are a valuable tool for this purpose, but few studies have focused on members of the genus Taphrina (Sjamsuridzal et al., 1997; Prillinger et al., 2000). Here, we report on the re-evaluation of species differentiation within the genus based on the comparative analysis of selected genetic characteristics of strains obtained from culture collections that represent about one-third of the currently recognized species, and argue for the use of molecular methods to identify the actual Taphrina species causing infections.
|
METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
. Species names conform with Mix (1949, 1954) and Gjaerum (1964, 1966). Host plant names follow the Germplasm Resources Information Network (GRIN) on-line database (USDA, ARS, National Genetic Resources Program, National Germplasm Resources Laboratory, Beltsville, MD, USA). Strains were obtained from the Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands (CBS) and the ARS Culture Collection, NCAUR, Peoria, IL, USA (NRRL). Additional strains were supplied by H. Prillinger, IAM, Vienna, Austria (HA strains) and F. Oberwinkler, University of Tübingen, Germany (F strains). One strain of T. deformans was isolated in Portugal from leaves of Prunus persica displaying peach leaf curl symptoms (AX1). Strains were maintained on yeast extract-malt extract (YM) agar slants at 4 °C.
|
without the final precipitation step. PCR amplification of polymorphic regions of genomic DNA using the microsatellite primers (GAC)5 and (GTG)5 (MSP-PCR) followed the protocol described in Gadanho et al. (2001) using 0·25 mM of each of the four dNTPs. Gel electrophoresis images were acquired with the Kodak Digital Science 1D image analysis software. DNA banding patterns were analysed with GELCOMPAR (version 4.1; Applied Maths) using Pearson's correlation coefficient and dendrograms were computed using the UPGMA clustering method. PCR amplification prior to sequencing employed primers NS7 (5'-GAGGCAATAACAGGTCTGTGATGC) or ITS5 (5'-GGAAGTAAAAGTCGTAACAAGG) and LR6 (5'-CGCCAGTTCTGCTTACC) using a Uno II thermal cycler (Biometra) and the resulting amplicon was purified with the GFX band purification kit (Amersham Pharmacia Biotech). Cycle sequencing of the D1/D2 variable domains of the 26S rDNA employed forward primer NL1 (5'-GCATATCAATAAGCGGAGGAAAAG) and reverse primer NL4 (5'-GGTCCGTGTTTCAAGACGG) and that of the internal transcribed spacer (ITS) region (comprising ITS1, 5.8S rRNA gene and ITS2) employed forward primer ITS1 (5'-TCCGTAGGTGAACCTGCGG) and reverse primer ITS4 (5'-TCCTCCGCTTATTGATATGC), following standard protocols. In a few cases, amplification for sequencing of the D1/D2 region employed primers NL1 and NL4. Sequences were obtained with an ALFexpress II DNA analyser (Amersham Biosciences), aligned with MegAlign (DNAStar software package) and visually corrected. Phylogenetic trees were computed with PAUP version 4.0b8 (Sinauer Associates) using the neighbour-joining method and Kimura's two-parameter model for calculating distances, or maximum-parsimony analysis (full heuristic search with the following options: random stepwise addition with 10 replications, branch swapping using tree bisection–reconnection and 100 maximum trees). Gaps were treated as missing data. GenBank accession numbers of D1/D2 (AF492024–AF492075) and ITS (AF492076–AF492129, AF494056) sequences are shown in Figs 1 and 2, together with additional sequences retrieved from GenBank.
|
|
|
RESULTS AND DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
) (data not shown). The similarity values between fingerprints obtained for strains of each pair, with both primers, were generally above 90 %, thus confirming not only the identity of the strains but also the reproducibility of the banding patterns. The ability of the selected primers to produce species-specific fingerprints was then investigated by the study of a larger set of strains (the dendrogram resulting from analysis of the combined banding patterns obtained with each of the two primers is available as supplementary material in IJSEM Online at http://ijs.sgmjournals.org). It was apparent that, in most cases, strains that were deemed to represent different species according to conventional criteria gave rise to distinct PCR fingerprints, whereas strains of the same species had similar banding patterns and clustered together in the dendrogram. However, there were some notable exceptions that may denote either misidentification of strains or misclassification of species. On the one hand, some strains of different species clustered together with both primers: e.g. T. betulina NRRL T-726, Taphrina carnea NRRL T-705 and Taphrina nana CBS 336.55; Taphrina tormentillae CBS 339.55 and T. carnea CBS 332.55; Taphrina pruni CBS 358.35 and Taphrina communis CBS 352.35; and Taphrina robinsoniana NRRL T-732 and T. betulina CBS 417.54. On the other hand, some strains deemed to be conspecific displayed very distinct PCR fingerprints and clustered separately with either primer: e.g. Taphrina caerulescens CBS 351.35 and NRRL T-878; Taphrina populina CBS 337.55 and NRRL Y-6300/Y-17788; T. betulina NRRL T-726 and CBS 417.54; T. robinsoniana NRRL T-732 and CBS 382.39; and T. carnea CBS 332.55 and NRRL T-705. The classification of these strains is discussed further below in the light of sequencing results.
rDNA sequencing
D1/D2 region.
All sequences from the D1/D2 domains of the 26S rDNA of Taphrina species (contained by primers NL1 and NL4) were 573–574 bp long. A mismatch was found in the sequence complementary to primer NL1 in runs with reverse primer NL4 (confirmed in runs with ITS1, the forward primer for the ITS region): a C instead of a G at position 16 of the primer (i.e. a G instead of a C at position 5 of reverse primer ITS4). This mismatch did not appear to affect annealing of the sequencing primers significantly. Only a few gaps were introduced by alignment with the sequences of selected archiascomycetes, Protomyces species and Saitoella complicata, retrieved from GenBank. Analysis of the sequence data is summarized in the phylogenetic tree depicted in Fig. 1. Tree topologies from neighbour-joining and maximum-parsimony analyses were similar and only the former is shown. Phylogenetic analysis confirmed the monophyletic nature of Taphrina (interspecies sequence divergence within the genus did not exceed 5 %) and its clear separation from the closely related genus Protomyces Unger (interspecies sequence divergence <4 %), with strong statistical support (Fig. 1). The same conclusion ensued from the work of Nishida & Sugiyama (1994) and Sjamsuridzal et al. (1997), based on 18S rDNA data. However, Taphrina vestergrenii, a fern parasite not included in those studies, appeared to occupy an intermediate position between the two genera (Fig. 1): it differed from the remaining Taphrina species in more than 35 positions (>6 % sequence divergence) and from Protomyces species in more than 50 positions (>9 % sequence divergence). A possible decision to accommodate T. vestergrenii in a separate genus should, however, await additional data on this taxon and the study of other species from ferns. A sequence retrieved from GenBank, corresponding to a yeast strain isolated from flower-dwelling insects and labelled Taphrina sp. (Lachance et al., 2001), also had an isolated position, but was apparently basal to both Taphrina and Protomyces (Fig. 1). The sequence of strain NRRL T-857 of T. deformans retrieved from GenBank was identical to that of strain CBS 356.35 determined in this study. However, another sequence retrieved from GenBank, corresponding to strain MZ109 and identified as T. deformans, had 5 nt differences from those of the two above-mentioned strains, but had a single insertion when compared with the sequence of T. tormentillae NRRL T-422 and might thus represent the latter species (Fig. 1). This strain was isolated from the surface of plasticized PVC blocks exposed to the air (Webb et al., 2000) and constitutes one of the rare examples of the isolation of Taphrina from substrates other than infected plant tissues (e.g. Kramer, 1987).
The D1/D2 region appears to be somewhat conserved within the genus and it did not allow the discrimination of all Taphrina species (e.g. Taphrina virginica and Taphrina wiesneri or Taphrina americana and T. purpurascens, which were separated on the basis of MSP-PCR fingerprints). In several cases, interspecies differences amounted to fewer than 3 nt positions (<0·5 % sequence divergence) (Fig. 1). Moreover, most of the internal branches had weak statistical support. Nevertheless, in some instances, the D1/D2 sequences concurred with the results of PCR fingerprinting in suggesting the conspecificity of strains that supposedly represented different species on the basis of conventional criteria: e.g. T. carnea CBS 332.55 and T. tormentillae NRRL T-422 or CBS 339.55 (1 or 2 nt substitutions); T. robinsoniana NRRL T-732 and T. betulina CBS 417.54 (no differences); and T. betulina NRRL T-726 and T. nana CBS 336.55 (no differences). Identity of strains from different collections (Taphrina letifera strains CBS 335.55 and NRRL T-791 and T. populina strains CBS 337.55 and NRRL T-497) was also corroborated by the D1/D2 data. On the other hand, intraspecific heterogeneity, already hinted at by the PCR fingerprinting results, can be anticipated when different D1/D2 sequences were obtained for strains of the same species: e.g. strains of T. caerulescens from Quercus alba (CBS 351.35) and Quercus macrocarpa (NRRL T-878) (8 nt substitutions); strains of T. robinsoniana from Alnus rugosa (CBS 382.39) and Alnus serrulata NRRL T-732 (7 substitutions); and strains of T. populina on Populus nigra from Sweden (CBS 337.55) and Canada (NRRL Y-6300) (3 substitutions). It is worth noting that, according to phylogenetic analysis of the D1/D2 sequences, species parasitic on Quercus spp. (Fagaceae) and Populus spp. (Salicaceae) and some of the species parasitic on the Betulaceae formed separate clusters. This correlation was not apparent in the phylogenetic analysis of the 18S rDNA sequence data of Sjamsuridzal et al. (1997), which also resulted in a phylogenetic tree with poorly resolved branches within the genus. The 14 authentic species of Taphrina included in that study could be discriminated by their 18S rDNA sequences (including T. virginica and T. wiesneri) although, in many cases, nucleotide differences amounted to less than 1 % overall divergence.
ITS region.
To address some of the unresolved issues mentioned above, sequences were determined from the less-conserved ITS region for a selected set of strains. Length polymorphisms were apparent within ITS1 and ITS2, which resulted in total base counts for the region (contained by primers ITS1 and ITS4) ranging from about 580 bp in Taphrina alni to 630 bp in T. populina and led to a few alignment ambiguities due to the presence of insertions/deletions. In contrast, the 5.8S rRNA gene was conserved throughout. The only ITS sequence available in GenBank was that of an unspecified strain of T. deformans, which differed from those of all the T. deformans strains studied by us (Table 1) in a single nucleotide insertion at the 5' end of ITS1. Phylogenetic analysis yielded the tree depicted in Fig. 2. As in the case of the D1/D2 region, tree topologies from neighbour-joining and maximum-parsimony analyses of the ITS sequences were similar and only the former is shown. A major difference between the D1/D2 and ITS trees is the relatively larger number of statistically supported clusters in the ITS tree, which is probably due to a higher rate of nucleotide substitution displayed by this region (in many cases, interspecies sequence divergence ranged between 5 and 15 %). Moreover, the number of parsimony-informative characters in the ITS region analysis was 172 out of a total of 642 (27 %), compared with 95 of 580 (16 %) in the D1/D2 region. As a consequence, species separations were more evident by ITS sequence analysis (interspecies differences: 
5 nt substitutions). This was especially apparent for taxa that could not be differentiated by their D1/D2 sequences: e.g. T. virginica and T. wiesneri or T. americana and T. purpurascens (Figs 1 and 2). Intraspecies differences amounted to no more than 4 nt substitutions, e.g. T. communis, Taphrina sadebeckii, T. wiesneri. However, other strains that supposedly represented distinct species had fewer than 4 base differences: T. virginica and Taphrina polystichi (3 substitutions); Taphrina epiphylla HA 1439 and T. sadebeckii HA 1345 (3 substitutions); T. tormentillae CBS 339.55 and T. carnea CBS 332.55 (2 substitutions); T. robinsoniana NRRL T-732 and T. betulina CBS 417.54 (no differences); and T. betulina NRRL T-726, T. carnea NRRL T-705 and T. nana CBS 336.55 (no differences). These cases will be discussed further below. It is interesting to note that clustering of species according to host plant family (or genus) is more evident in the ITS tree (Fig. 2). For example, all species parasitic on Prunus spp. are found on a single, well-supported branch. In addition, species on Quercus spp. and Populus spp. and some of the species parasitic on the Betulaceae clustered separately, as already observed in the D1/D2 tree.
Species delimitation
Species parasitic on Betulaceae.
Of the species parasitic on Alnus spp., T. alni and Taphrina tosquinetii were genetically homogeneous and well separated, T. sadebeckii displayed some intraspecific genetic variability and close proximity to T. epiphylla, whereas T. robinsoniana appeared to be heterogeneous (based on PCR fingerprints, D1/D2 and ITS sequences; e.g. Fig. 2). Relatedness between T. epiphylla (the cause of witches' brooms on Alnus incana) and T. sadebeckii (the cause of leaf spots on Alnus glutinosa) is supported by all the data obtained in the present study. Gjaerum (1964) had suggested that the latter is a synonym of the former, an opinion not shared by other authors (Mix, 1949; Bacigálová, 1994). Due to the genetic variability found among strains of T. sadebeckii in terms of PCR fingerprints (data not shown) and ITS sequences (Fig. 2), a decision to keep the two species separate requires the study of additional strains of T. epiphylla. PCR fingerprints (data not shown) and sequence data (Fig. 2) suggest conspecificity of T. robinsoniana NRRL T-732 and T. betulina CBS 417.54. However, synonymy of the two species is unlikely, due to the different nature and geographical distribution of the respective host plants (Table 1; Mix, 1949). Moreover, additional strains of each species (T. robinsoniana CBS 382.39 and T. betulina NRRL T-726) had very different ITS sequences and clustered on separate branches (Fig. 2). It is interesting to note that the two strains of T. robinsoniana clustered together with T. alni in the D1/D2 and ITS trees (Fig. 2), both species producing typical outgrowths (‘tongues’) on female catkins, albeit on distinct Alnus species: the first on North American alders (Alnus rugosa or Alnus serrulata) and the second on a European species (Alnus incana) (Table 1). It is possible that, as currently circumscribed (Mix, 1949, 1954), T. robinsoniana is heterogeneous and that the forms on Alnus rugosa (represented by strain CBS 382.39) and Alnus serrulata (NRRL T-732) are actually separate species. The situation of T. betulina CBS 417.54 is more difficult to explain, and this strain may have been misidentified or mislabelled. The other strain of T. betulina, NRRL T-726, clustered on the ITS tree with other species from birches (Fig. 2): T. carnea (represented by strain NRRL T-705), a species that causes leaf curl on Betula intermedia (=Betula pubescens?); T. nana, a species that induces witches' brooms on Betula nana; and T. americana, another species that induces witches' brooms but on a North American birch, Betula fontinalis (=Betula occidentalis) (Table 1; Mix, 1949). The molecular data point to the conspecificity of the species on European birches, T. betulina (represented by NRRL T-726), T. carnea (NRRL T-705) and T. nana (CBS 336·55), but support the separation of T. americana at the species level. A second strain of T. carnea, CBS 332.55, appeared to be conspecific with the two strains of T. tormentillae according to molecular data (Figs 1 and 2), an observation that suggests a possible misidentification of the former, since there are marked differences in host specificity and geographical distribution of each species (Table 1).
Possible conspecificity between T. virginica and T. polystichi was suggested by the sequence data (Figs 1 and 2), but not necessarily by the respective PCR fingerprints (data not shown), and it is highly unlikely due to the very different nature of the respective host plants (Table 1). Their closest relative on the ITS tree (Fig. 2) appears to be Taphrina carpini, a species that, like T. virginica, is also parasitic on a member of the Betulaceae (Table 1; Mix, 1949). The placement of T. polystichi was thus quite unexpected, considering the very distinct phylogenetic position of the other species parasitic on ferns (T. vestergrenii) included in the present study (Fig. 1). A final decision on the status of T. virginica and T. polystichi would be premature at this stage and should await the study of additional strains of both species.
Species parasitic on Prunus.
The results of PCR fingerprinting of all the strains representing species parasitic on Prunus spp. are shown in Fig. 3. T. purpurascens and T. tormentillae were also included; the former due to its apparent relatedness to T. communis (Fig. 2) and the latter since it represents the only other species parasitic on a different genus of the Rosaceae (Table 1). The different species appeared to be adequately discriminated by their PCR fingerprints (Fig. 3) and ITS sequences (Fig. 2), but not by the D1/D2 data (not shown). Several species were genetically homogeneous, namely Taphrina confusa, T. deformans, Taphrina flavorubra and Taphrina padi. PCR fingerprints of T. deformans strains showed some variability (Fig. 3), but they always clustered together and no nucleotide differences were found among them in the ITS sequences (Fig. 2). Of the species that deform fruits (plum pockets) and/or shoots, T. communis, T. flavorubra, Taphrina mirabilis and Taphrina pruni-subcordatae, which are parasitic on North American Prunus spp., formed a well-supported clade on the ITS tree (Fig. 2). Species separations appeared to parallel those of the hosts (Table 1). Surprisingly, T. pruni CBS 358.35 and T. purpurascens CBS 338.55 clustered with the strains of T. communis (number of base differences among the five strains ranged from 1 to 4; Fig. 2), an observation that is also supported by the MSP-PCR results (Fig. 3). T. pruni CBS 358.35 was apparently isolated from Prunus domestica, but its geographical origin is not known (CBS Yeast Database). In the light of the molecular data, it is likely that it originated in North America and should thus be transferred to T. communis, lending support to Mix's statement that ‘plum pockets found on domestica plums in [the USA] should be ascribed to T. communis’ (Mix, 1949). In agreement with this hypothesis, two T. pruni strains from European plums (HA 1306 from Prunus domestica and HA 1340 from Prunus spinosa; Table 1) were genetically distinct from T. communis (Figs 2 and 3) and appear to be authentic representatives of the former species (the two forms most likely being conspecific; Figs 2 and 3). The position of T. purpurascens is more difficult to explain, as this species produces leaf curl on Rhus copallinum, a member of the Anacardiaceae (Table 1; Mix, 1949). A formal proposal to consider T. purpurascens as a synonym of T. communis would be premature at this stage and should await the study of additional strains of the former species. To sum up, T. communis should therefore include all forms that cause plum pockets on Prunus americana, Prunus domestica and Prunus nigra in North America, although the latter, represented by strain NRRL T-755, showed some deviation in the PCR fingerprints (Fig. 3).
|
, but the results of the molecular characterization suggest otherwise: the two strains had a single nucleotide substitution in the ITS region between them and in spite of being closely related to the T. communis cluster (Fig. 2), differed from the latter in two insertions and at least 6 nt substitutions. In spite of the genetic variability displayed by the two strains of T. mirabilis [they clustered together on the MSP-PCR dendrogram but at low similarity (Fig. 3) and differed by 2 bp in the D1/D2 region] and by the strains of the T. communis cluster, it seems reasonable to keep the two species separate, although a final decision would benefit from additional data (e.g. results of DNA–DNA hybridization experiments) and the study of more strains.
T. padi, a species that causes deformed fruits on Prunus padus in Europe, has been considered synonymous with T. pruni (e.g. Mix, 1936), but Mix (1949) sustained their separation, stating that T. padi was more closely related to T. confusa than to T. pruni. Our results (Fig. 2) fully corroborate Mix's hypothesis, and a recent study by Prillinger et al. (2000) has also confirmed the separation of T. padi from T. pruni based on RAPD analysis and on partial 18S rDNA sequences.
T. wiesneri induces witches' brooms on cherry trees and has forms on different species throughout the world (Mix, 1949). Our molecular data suggest that the strains from Prunus avium (F-297, NRRL T-293 and HA 1437) and Prunus fruticosa (HA 1388) in Europe are probably conspecific, although the latter shows some deviation in its PCR fingerprints (Fig. 3) and ITS sequence (Fig. 2). Strain NRRL T-460, representing the form on the North American Prunus pennsylvanica, most probably represents a separate species, a hypothesis that is corroborated by the PCR fingerprinting and ITS data (Figs 2 and 3). Future studies including strains from Japanese cherry trees will undoubtedly help to ascertain whether there are additional species within T. wiesneri.
Concluding remarks
Analysis of the molecular data determined in this study revealed that Taphrina species previously defined on the basis of conventional criteria (host plant, geographical origin, type of infection symptom and/or ascus morphology) were, in most cases, genetically distinct. MSP-PCR fingerprinting adequately discriminated the majority of Taphrina species and proved to be a reproducible and simple method that allowed the rapid analysis of large numbers of strains. Of the sequenced rDNA regions, D1/D2 was somewhat conserved and did not allow the discrimination of all Taphrina species, but phylogenetic analysis showed the genus Taphrina to be monophyletic (probably excluding T. vestergrenii) and confirmed its distinction from the closely related genus Protomyces. The ITS region appeared to be more adequate for species discrimination and phylogenetic reconstruction within the genus. Furthermore, clustering of Taphrina species according to ITS sequence data corresponded grossly to host plant genera (and/or families), namely for species parasitic on Quercus (Fagaceae), Populus (Salicaceae), Prunus (Rosaceae), Alnus or Betula (Betulaceae) and possibly also on Acer (Aceraceae). This evidence constitutes a strong indication of the importance of co-evolution in the speciation of Taphrina species, as has been found for other genera of phytopathogenic fungi (e.g. Bakkeren et al., 2000). In a few cases, a correlation was also observed between the clustering of Taphrina species in the ITS tree and the type of infection symptom (e.g. species inducing tongues on Alnus or species causing fruit pockets on Prunus; Fig. 2). The results of PCR fingerprinting and ITS sequencing additionally suggested some cases of possible conspecificity (e.g. T. betulina, T. carnea and T. nana), others of intraspecific heterogeneity (T. caerulescens, T. populina, T. robinsoniana, T. wiesneri) and yet others of mislabelled or misidentified strains: e.g. T. carnea CBS 332.55 (=T. tormentillae); T. betulina CBS 417.54 (=T. robinsoniana); T. purpurascens CBS 338.55 (=T. communis); and T. pruni CBS 358.35 (=T. communis). Confirmation of some of these hypotheses would benefit from the study of additional isolates and the implementation of inoculation experiments.
In our view, progress in the systematics and phylogeny of Taphrina will undoubtedly require the isolation and study of more cultures of the many species that have been recognized but are not currently available (Mix, 1949). It is our hope that this study will stimulate a renewed interest in the genus Taphrina by providing the tools that enable the accurate diagnosis of the various infections caused by the different species, e.g. by direct amplification and sequencing of the appropriate rDNA regions from infected tissues, without the need for isolation of the yeast phase. These approaches will conceivably lead to a more complete knowledge of the biology and ecology of these widespread phytopathogenic fungi.
|
ACKNOWLEDGEMENTS |
|---|
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
Bacigálová, K. (1994). Species of Taphrina on Alnus in Slovakia. Czech Mycol 47, 223–236.
Bacigálová, K. (1997). Ecological notes to the distribution of Taphrinales fungi in Slovakia. Biologia (Bratisl) 52, 7–10.
Bakkeren, G., Kronstad, J. W. & Lévesque, C. A. (2000). Comparison of AFLP fingerprints and ITS sequences as phylogenetic markers in Ustilaginomycetes. Mycologia 92, 510–521.
Eriksson, O. E. & Winka, K. (1997). Supraordinal taxa of Ascomycota. Myconet 1, 1–16.
Gadanho, M., Sampaio, J. P. & Spencer-Martins, I. (2001). Polyphasic taxonomy of the basidiomycetous yeast genus Rhodosporidium: R. azoricum sp. nov. Can J Microbiol 47, 213–221.[Medline]
Gjaerum, H. B. (1964). The genus Taphrina Fr. in Norway. Nytt Mag Bot 11, 5–26.
Gjaerum, H. B. (1966). Oretunge forarsaket av Taphrina alni (B. & Br.) n. comb. i Norge. Blyttia 24, 188–195 (in Norwegian).
Heath, I. B., Ashton, M.-L., Rethoret, K. & Heath, M. C. (1982). Mitosis and the phylogeny of Taphrina. Can J Bot 60, 1696–1725.
Kramer, C. L. (1987). The Taphrinales. In The Expanding Realm of Yeast-like Fungi, pp. 151–166. Edited by G. S. de Hoog, M. Th. Smith & A. C. J. Weijman. Amsterdam: Elsevier.
Kurtzman, C. P. & Sugiyama, J. (2001). Ascomycetous yeasts and yeast-like taxa. In The Mycota, vol. VIIA, pp. 179–200. Edited by D. J. McLaughlin, E. G. McLaughlin & P. A. Lemke. Berlin: Springer.
Lachance, M.-A., Starmer, W. T., Rosa, C. A., Bowles, J. M., Barker, J. S. F. & Janzen, D. H. (2001). Biogeography of the yeasts of ephemeral flowers and their insects. FEMS Yeast Res 1, 1–8.[Medline]
Mix, A. J. (1935). The life history of Taphrina deformans. Phytopathology 25, 41–66.
Mix, A. J. (1936). The genus Taphrina. II: a list of valid species. Univ Kans Sci Bull 24, 151–176.
Mix, A. J. (1949). A monograph of the genus Taphrina. Univ Kans Sci Bull 33, 3–167.
Mix, A. J. (1954). Additions and emendations to a monograph of the genus Taphrina. Trans Kans Acad Sci 57, 55–65.
Moore, R. T. (1998). Lalaria R. T. Moore. In The Yeasts, a Taxonomic Study, 4th edn, pp. 77–100. Edited by C. P. Kurtzman & J. W. Fell. Amsterdam: Elsevier.
Nishida, H. & Sugiyama, J. (1994). Archiascomycetes: detection of a major new lineage within the Ascomycota. Mycoscience 35, 361–366.[CrossRef]
Prillinger, H., Dörfler, Ch., Laaser, G., Eckerlein, B. & Lehle, L. (1990). Ein Beitrag zur Systematik und Entwicklungsbiologie höherer Pilze: Hefe-Typen der Basidiomyceten. Teil I: Schizosaccharomycetales, Protomyces-Typ. Z Mykol 56, 219–250.
Prillinger, H., Bacigálová, K., Lopandic, K. & Binder, M. (2000). Taphrina padi in Bayern und der Slowakei. Hoppea Denkschr Regensb Bot Ges 61, 275–294.
Sjamsuridzal, W., Tajiri, Y., Nishida, H., Thuan, T., Kawasaki, H., Hirata, A., Yokota, A. & Sugiyama, J. (1997). Evolutionary relationships of members of the genera Taphrina, Protomyces, Schizosaccharomyces, and related taxa within the archiascomycetes: Integrated analysis of genotypic and phenotypic characters. Mycoscience 38, 267–280.[CrossRef]
Webb, J. S., Nixon, M., Eastwood, I. M., Greenhalgh, M., Robson, G. D. & Handley, P. S. (2000). Fungal colonization and biodeterioration of plasticized polyvinyl chloride. Appl Environ Microbiol 66, 3194–3200.
This article has been cited by other articles:
|
|
 |
|
  J. Sugiyama, K. Hosaka, and S.-O. Suh Early diverging Ascomycota: phylogenetic divergence and related evolutionary enigmas Mycologia, November 1, 2006; 98(6): 996 - 1005. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| INT J SYST EVOL MICROBIOL | MICROBIOLOGY | J GEN VIROL |
| J MED MICROBIOL | ALL SGM JOURNALS | |
