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1 Centraalbureau voor Schimmelcultures, Fungal Biodiversity Centre, P.O. Box
85167, 3508 AD, Utrecht, The Netherlands
2 Department of Microbiology and Plant Pathology, Forestry and Agricultural
Biotechnology Institute, University of Pretoria, South Africa
3 PROMEC Unit, Medical Research Council, P.O. Box 19070, 7505 Tygerberg,
South Africa
4 Centro de Recursos Microbiológicos, Faculdade de Ciências e
Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica,
Portugal
5 Centro de Biologia Celular, Departamento de Biologia, Universidade de
Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro,
Portugal
6 School of Biological Sciences & Biotechnology, Murdoch University,
Murdoch 6150, WA, Australia
*
Correspondence: Pedro W. Crous,
crous{at}cbs.knaw.nl
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Abstract |
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 TOP Abstract INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Taxonomic novelties: Neofusicoccum Crous, Slippers & A.J.L. Phillips gen. nov., Neofusicoccum andinum (Mohali, Slippers & M.J. Wingf.) Mohali, Slippers & M.J. Wingf. comb. nov., Neofusicoccum arbuti (D.F. Farr & M. Elliott) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum australe (Slippers, Crous & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum eucalypticola (Slippers Crous & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum eucalyptorum (Crous, H. Smith & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum luteum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum macroclavatum (Burgess, Barber & Hardy) Burgess, Barber & Hardy comb. nov., Neofusicoccum mangiferae (Syd. & P. Syd.) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum protearum (Denman & Crous) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum ribis (Slippers, Crous & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum viticlavatum (Niekerk & Crous) Crous, Slippers & A.J.L. Phillips comb. nov., Neofusicoccum vitifusiforme (Niekerk & Crous) Crous, Slippers & A.J.L. Phillips comb. nov., Neoscytalidium Crous & Slippers gen. nov., Neoscytalidium dimidiatum (Penz.) Crous & Slippers comb. nov., Pseudofusicoccum (Mohali, Slippers & M.J. Wingf.) Mohali, Slippers & M.J. Wingf. gen. nov., Pseudofusicoccum stromaticum (Mohali, Slippers & M.J. Wingf.) Mohali, Slippers & M.J. Wingf. comb. nov.
Keywords Ascomycetes / Botryosphaeria / Botryosphaeriaceae / Diplodia / Dothiorella / Fusicoccum / Lasiodiplodia / Macrophomina / Natrassia / Neofusicoccum / Neoscytalidium / Pseudofusicoccum / Scytalidium / Stenocarpella / Tiarosporella / systematics
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INTRODUCTION |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Botryosphaeria has been well circumscribed, and can be defined as forming uni- to multilocular ascomata with multi-layered walls, occurring singly or in clusters, often intermixed with conidiomata, which are pycnidial. Asci are bitunicate, with a thick endotunica, stalked or sessile, clavate, with a well-developed apical chamber, forming in a basal hymenial layer, intermixed among hyaline pseudoparaphyses that are frequently constricted at the septa. Ascospores are hyaline, aseptate, fusoid to ellipsoid or ovoid, bi- to triseriate, mostly without a mucoid sheath or appendages; ascospores turn brown and become septate and even slightly verruculose upon germination (von Arx & Müller 1954, Shoemaker 1964, Eriksson 1981, Sivanesan 1984, Denman et al. 2000, Alves et al. 2004).
Theissen & Sydow (1915) placed Botryosphaeria in the Botryosphaerieae, a sub-family of the Pseudosphaeriaceae, which was not assigned to any specific order. The Pseudosphaeriaceae was later placed in the Myriangiales (Theissen 1916), and in 1917 Theissen & Sydow were of the opinion that the Pseudosphaeriaceae should be united with the Dothideaceae (Luttrell 1951). The Dothideales were characterised by the formation of asci in locules embedded in stromata, and contained the Dothideaceae, a family established to accommodate multiloculate forms like Botryosphaeria. Petrak (1923) placed Botryosphaeria in the sub-family Pseudosphaerieae, which was placed in the Pleosporaceae (Sphaeriales).
Miller (1928) placed Botryosphaeria in the Dothideales because true perithecial walls were absent. He later recognised three orders, namely the Sphaeriales (with perithecia and paraphyses), the Dothideales (ascostromatic forms without paraphyses), and the Pseudosphaeriales (ascostromatic forms with interthecial threads) and assigned Botryosphaeria to the Pseudosphaeriales.
Luttrell (1955) identified eight types of centrum development, and highlighted the taxonomic value of sterile, interthecial tissues in the taxonomy of the Ascomycetes. He furthermore replaced the name Pseudosphaeriales with Pleosporales, and assigned Botryosphaeria to this order. Luttrell's views were supported by Eriksson (1981) and Barr (1987). The orders proposed by Luttrell and Barr were not accepted by von Arx & Müller (1975) and von Arx (1987), as they comprised a mixture of unrelated genera (von Arx 1987). Von Arx & Müller (1975) only delimited the Dothideales, with two sub-orders and 24 families. Their view was that this was a more appropriate means of dealing with the taxonomy of this very large heterogeneous group, at least until a more natural method of classification could be developed. Thus, Botryosphaeria was maintained in the Botryosphaeriaceae, but retained in the Dothideales. This delimitation is widely accepted and the Dictionary of Fungi accommodates Botryosphaeria in the Botryosphaeriaceae, and the Dothideales (Kirk et al. 2001). Although the Botryosphaeriaceae is treated in the present study, its ordinal position in the Dothideomycetes will be treated elsewhere as part of the AToL (Assembling the Tree of Life) project (Schoch et al., in prep.).
Anamorphs of Botryosphaeria have been assigned to 18 coelomycete
genera, of which only two were recognised by Denman et al.
(2000). This taxonomic
subdivision was supported by comparisons of ITS sequence data, which separated
the examined Botryosphaeria spp. into two groups, correlating to
those species with Diplodia-like anamorphs and those with
Fusicoccum-like anamorphs (Jacobs
& Rehner 1998, Denman
et al. 2000). Later studies including additional species
and a larger suite of DNA-based markers supported this view
(Zhou & Stanosz 2001,
Alves et al. 2004,
Slippers et al.
2004). However, this apparently clear sub-division is questioned
by Saccharata proteae Denman & Crous (as Botryosphaeria
proteae (Wakef.) Denman & Crous with Fusicoccum and
Diplodia synanamorphs), which is morphologically and phylogenetically
distinct from representatives of the Diplodia- and
Fusicoccum-like groups (Crous
et al. 2004). Some authors have continued to use
Lasiodiplodia Ellis & Everh. as a genus distinct from
Diplodia Fr., because of its distinct phylogenetic (usually ITS or
EF-1
) and morphological (striate conidia and paraphyses)
characteristics (Pavlic et al.
2004). Recently, the name Dothiorella Sacc. has also been
re-introduced as a distinct Botryosphaeria anamorph (conidia brown,
septate while still attached to the conidiogenous cells)
(Phillips et al.
2005a) and Dichomera Cooke has been linked to
Botryosphaeria species with Fusicoccum anamorphs
(Barber et al. 2005).
Many of the other 18 coelomycete genera linked to Botryosphaeria
remain untested in terms of phylogenetic association to the above groups.
The representation and phylogenetic understanding of major groups within
Botryosphaeria remains poor. Previous analyses based on DNA sequence
comparisons have included limited numbers of species, not representing the
full anamorph diversity associated with Botryosphaeria. The value of
the intron-dominated sequences of the ITS, β-tubulin and EF 1-
loci (on which most previous studies were based) to infer phylogenetic
relationships across the diversity of the genus, is also unclear. The more
conserved mtSSU data have, for example, suggested that B. dothidea
and B. corticis (Demaree & Wilcox) Arx & E. Müll. are
unrelated to Fusicoccum s.str.
(Zhou & Stanosz 2001) even
though they are typically assigned to this genus.
Botryosphaeria as a single genus is clearly unaligned with evolutionary radiations in the group, as exemplified by the morphologically and phylogenetically distinct anamorph genera linked to it. A preferable approach would be natural unit classification, also referred to as the "genus for genus concept" (Seifert et al. 2000). Here, morphologically distinct anamorph genera are linked to unique teleomorphs on a one for one basis, correlating with phylogenetic DNA data. This is an approach that has been applied to genera such as Calonectria De Not. (Crous 2002), Cryphonectria (Sacc.) Sacc. & D. Sacc. (Gryzenhout et al. 2006 – this volume), Ophiostoma Syd. & P. Syd. (Zipfel et al. 2006 – this volume) and Botryosphaeria (Rossman & Samuels 2005). The primary aim of the present study is to delineate the phylogenetic lineages of the Botryosphaeriaceae, and to discuss the morphological differences and generic concepts that can be ascribed to them. For this purpose, we have chosen comparisons of sequences for the 28S rRNA gene (LSU) because of its favourable size (approx. 900–1000 bp. used), and its relatively conserved (medium–high level) nature, suitable to consider taxonomic sub-divisions at the generic level.
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MATERIALS AND METHODS |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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DNA phylogeny
The isolation protocol of Lee & Taylor
(1990) was used to extract
genomic DNA from fungal mycelia grown on MEA. The primers ITS1
(White et al. 1990)
and LR5 (Vilgalys & Hester
1990) were used to amplify part of the nuclear rRNA operon using
the PCR conditions recommended by the authors and spanning the 3' end of the
18S rRNA gene, the internal spacers, the 5.8S rRNA gene and a part of the 5'
end of the 28S rRNA gene. PCR products were separated by electrophoresis at 80
V for 1 h in a 0.8 % (w/v) agarose gel in 0.5x TAE running buffer (0.4
M Tris, 0.05 M NaAc, and 0.01 M EDTA, pH
7.85) and visualised under UV light using a GeneGenius Gel Documentation and
Analysis System (Syngene, Cambridge, U.K.) following ethidium bromide
staining. The amplification products were purified using a GFX PCR DNA and Gel
Band Purification Kit (Amersham Pharmacia Biotech Europe GmbH, Germany). The
purified products were sequenced in both directions using an ABI PRISM Big Dye
Terminator v. 3.1 Cycle Sequencing Ready Reaction Kit (PE Biosystems, Foster
City, CA) containing AmpliTaq DNA Polymerase as recommended by the
manufacturer. The primers LR0R (Rehner
& Samuels 1994), LR3R
(http://www.biology.duke.edu/fungi/mycolab/primers.htm),
LR16 (Moncalvo et al.
1993), and LR5 (Vilgalys &
Hester 1990) were used to ensure good quality sequences over the
entire length of the amplicon. The resulting fragments were analysed on an ABI
Prism 3100 DNA Sequencer (Perkin-Elmer, Norwalk, CN).
DNA sequences were assembled and added to the outgroups and additional GenBank sequences using Sequence Alignment Editor v. 2.0a11 (Rambaut 2002), and manual adjustments for improvement were made by eye where necessary. The phylogenetic analyses of sequence data were done in PAUP (Phylogenetic Analysis Using Parsimony) version 4.0b10 (Swofford 2002) and consisted of neighbour-joining analysis with the uncorrected ("p"), the Kimura 2-parameter and the HKY85 substitution model in PAUP. Alignment gaps were treated as missing data and all characters were unordered and of equal weight. Any ties were broken randomly when encountered. For parsimony analysis, alignment gaps were treated as both missing and as a fifth character state and all characters were unordered and of equal weight. Maximum parsimony analysis was performed using the heuristic search option with simple taxa additions and tree bisection and reconstruction (TBR) as the branch-swapping algorithm. Branches of zero length were collapsed and all multiple, equally parsimonious trees were saved. The robustness of the trees obtained was evaluated by 1000 bootstrap replications (Hillis & Bull 1993). Tree length (TL), consistency index (CI), retention index (RI) and rescaled consistency index (RC) were calculated and the resulting trees were printed with TreeView v. 1.6.6 (Page 1996).
Bayesian analysis was conducted on the same aligned LSU dataset as the distance analysis. First MrModeltest v. 2.2 (Nylander 2004) was used to determine the best nucleotide substitution model. Phylogenetic analyses were performed with MrBayes v. 3 (Ronquist & Huelsenbeck 2003) applying a general time-reversible (GTR) substitution model with gamma (G) and proportion of invariable site (I) parameters to accommodate variable rates across sites. The Markov Chain Monte Carlo (MCMC) analysis of 4 chains started from random tree topology and lasted 10 000 000 generations. Trees were saved each 100 000 generations, resulting in 1000 saved trees. Burn-in was set at 500 000 generations after which the likelihood values were stationary, leaving 950 trees from which the consensus trees and posterior probabilities were calculated. PAUP 4.0b10 was used to reconstruct the consensus tree, and maximum posterior probabilities were assigned to branches after a 50 % majority rule consensus tree was constructed from the 950 sampled trees.
Taxonomy
Morphological descriptions were made for isolates sporulating on 2 % water
agar (WA) with sterilised pine needles as substratum, at 25 °C under
near-UV light, to induce sporulation. Structures were mounted in lactic acid,
and 30 measurements at x 1000 magnification were made of each structure
where possible. The 95 % confidence levels were determined, and the extremes
of spore measurements given in parentheses. All cultures used in this study
are maintained in the CBS culture collection.
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RESULTS |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Twelve clades could be identified in the distance tree obtained using the HKY85 substitution model (Fig 1). These are discussed in the Taxonomy and Discussion sections. Parsimony analysis with gaps treated as missing characters yielded 79604 equally parsimonious trees (TL = 582 steps; CI = 0.509; RI = 0.905; RC = 0.460). Treating gaps as new states resulted in 79775 equally parsimonious trees (TL = 603 steps; CI = 0.524; RI = 0.910; RC = 0.477). The strict consensus trees calculated from the equally parsimonious trees were identical to each other and are shown in TreeBASE. Between the neighbour-joining and parsimony analyses, the same clades were supported with two exceptions. The first exception is Botryosphaeria mamane D.E. Gardner (CBS 117444), which resides in Clade 3 (Fig. 1), but is basal to Clades 1 to 6 in the strict consensus trees. Also, Clade 7 groups with Clade 10 in the strict consensus trees, but this is not supported with a bootstrap analysis (data not shown).
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Bayesian analysis resulted in a tree with largely the same topology and clades (Fig. 2). Differences observed were related to the position of B. mamane, which clustered close to Clade 3 in the distance analysis, but clustered in Clade 4 in the Bayesian analysis. A further difference was that in the Bayesian analysis Clades 8–9 clustered basal to the Botryosphaeriaceae.
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Clade 1 includes species with Diplodia, Sphaeropsis Sacc. and
Lasiodiplodia anamorphs clustering together. Although sequences of
gene regions such as ITS, EF-1 and β-tubulin, support the synonymy
of Sphaeropsis under Diplodia, in various cases they
separate Lasiodiplodia from the Diplodia clade
(Pavlic et al. 2004,
Phillips et al.
2005a). This is in contrast to the LSU dataset
(Fig. 1) in which species
having Diplodia anamorphs could not be separated from those in
Lasiodiplodia. Inclusion of additional strains resulted in a basal
polytomy with low bootstrap support. Furthermore, uncertainty remains as to
which teleomorph name is best suited for this clade, as the form genus
Diplodia is known to be polyphyletic
(Sutton 1980,
Sivanesan 1984). The
clustering of three species of Tiarosporella Höhn. in this clade
was also unexpected.
Clade 2 is represented by the type species of the genus Botryosphaeria, namely B. dothidea, and its anamorph Fusicoccum aesculi Corda. The genus Macrophomopsis N.E. Stevens & Baechler, represented by a strain identified as M. coronillae (Desm.) Petr. (type species) (CBS 769.71), clusters in this clade, as does the genus Dichomera Cooke, represented by a strain identified as D. saubinetii (Mont.) Cooke (type species) (CBS 990.70).
Clade 3 is represented by isolates of Macrophomina phaseolina (Tassi) Goid. This fungus is the coelomycete synanamorph of "Rhizoctonia" bataticola (Taubenh.) E.J. Butler, which is shown to be a member of the Botryosphaeriaceae. Conidia also have apical mucous appendages early in their development, which has in the past led to confusion, and the allocation of this species to the genus Tiarosporella (von Arx 1981). With age, conidia lose their apical appendages, and become brown and slightly roughened, appearing more Diplodia-like in morphology.
Clade 4 represents Fusicoccum dimidiatum (Penz.) D.F. Farr. This species, which has a large number of synonyms (Farr et al. 2005), is unusual in having a Fusicoccum-like coelomycete anamorph (with mucoid apical appendages). It also has a powdery Scytalidium-like hyphomycete synanamorph that is lacking in other species in the Botryosphaeriaceae. Scytalidium, typified by S. lignicola Pesante (CBS 233.57) clusters outside of the Botryosphaeriaceae. However, DNA sequence data derived from the Scytalidium species present in the CBS collection lead us to conclude that this genus is also polyphyletic (results not given).
Botryosphaeria mamane has a Fusicoccum anamorph and clusters most closely with species in either Clade 3 or Clade 4 in the various analyses. The Fusicoccum anamorph is morphologically most similar to species residing in Clade 2 (Fusicoccum s.str.). It does not have the apical appendages or discoloration found in species residing in Clade 3, nor does it have a Scytalidium-like synanamorph occurring in species residing in Clade 4. Consequenctly, its taxomic position remains unresolved.
Clade 5 represents Botryosphaeria-like teleomorphs with pigmented, septate ascospores for which the genus Dothidotthia Höhn. is available (Barr 1987, 1989). Anamorphs of this genus reside in Dothiorella Sacc. (Phillips et al. 2005a).
Clade 6 represents Botryosphaeria-like species with Fusicoccum-like anamorphs and Dichomera-like synanamorphs, for which the name Neofusicoccum gen. nov. is introduced. The Dichomera-like synanamorphs in this clade are characterised by globose to pyriform conidia. The older, brown conidia in Clade 2 (Botryosphaeria s.str.) are obovoid, ellipsoid or fusiform, never globose or subglobose (Phillips et al. 2005b, Barber et al. 2005).
Clade 7 represents isolates of "Fusicoccum"stromaticum Mohali, Slippers & M.J. Wingf. (Mohali et al. 2006). This taxon is distinguished from Fusicoccum aesculi and other Fusicoccum-like genera by having conidia that are enclosed in a persistent mucous sheath, for which the genus Pseudofusicoccum is proposed.
Clade 8 is represented by a single species, Botryosphaeria quercuum (Schwein.) Sacc., for which the genus Melanops Nitschke ex Fuckel is available. Saccharata Denman & Crous (anamorph Fusicoccum-like; synanamorph Diplodia-like) (Clade 9) is morphologically distinguished from Botryosphaeria s. str. by having unilocular ascomata that develop under a clypeus.
Clade 10 includes species of Guignardia Viala & Ravaz with Phyllosticta Pers. anamorphs (Van der Aa & Vanev 2002). Clade 11 contains several distinct genera, namely Camarosporium Schulzer [type = C. quaternatum (Hazsl.) Sacc.], "Phyllosticta" flevolandica Aa, and other morphologically distinct taxa. "Diplodia" macrospora Earle and "Diplodia" maydis (Berk.) Sacc. (Clade 12) are shown to be distinct from the Botryosphaeriaceae. Stenocarpella Syd. & P. Syd. is appropriate for them, as they cluster apart from the Botryosphaeriaceae. Surprisingly, they cluster in the Diaporthales although no teleomorph connections are currently known for species of Stenocarpella.
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DISCUSSION |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Clade 1: Diplodia/Lasiodiplodia (several teleomorph genera available)
Species in Clade 1 are poorly resolved in both distance and Bayesian
analyses. This is due to the few informative sites in this clade (19) in the
section of LSU selected for this study. A larger segment of the LSU or
additional gene regions will be required to resolve the phylogenetic
relationships of species residing in this clade.
In the past, anamorphs of Botryosphaeria have been described in up to 18 different genera (Denman et al. 2000), many of which were not clearly defined and contain dark conidia typical or similar to those typical of Diplodia. Sutton (1980) reduced Macrophoma (Sacc.) Berl. & Voglino to synonymy with Sphaeropsis. Pennycook & Samuels (1985) reduced Macrophomopsis to synonymy with Fusicoccum. Crous & Palm (1999) showed that Botryodiplodia (Sacc.) Sacc. was a nomen dubium, and reduced Dothiorella to synonymy with Diplodia. Denman et al. (2000) also regarded Sphaeropsis and Lasiodiplodia as synonyms of Diplodia. Phillips et al. (2005a) again separated Dothiorella from Diplodia, and also provided evidence to show that the teleomorphs were different.
Recent treatments of Botryosphaeria anamorphs have revealed that they cluster in two clades, namely Diplodia (dark, mostly >10 µm broad, thick-walled conidia), and Fusicoccum (hyaline, mostly <10 µm broad, thin-walled conidia) (Jacobs & Rehner 1998, Denman et al. 2000, Zhou & Stanosz 2001, Alves et al. 2004). With age, however, conidia in species of Fusicoccum become dark, and frequently also septate. This complicates identification, especially where this is attempted based on structures occurring on natural substrates and in the absence of fresh cultures.
Pavlic et al. (2004) described a new species of Lasiodiplodia based on its characteristic conidial ornamentation typical of the genus (von Arx 1987). Xiao & Rogers (2004) described a new species of Diplodia, and placed it in Sphaeropsis. The correct generic names to be used for the dark-spored anamorphs of Botryosphaeria thus remains uncertain.
The genus Sphaeropsis is based on S. visci (Fr.) Sacc., while the genus Lasiodiplodia is based on L. theobromae (Pat.) Griff. & Maubl. In the present study we included cultures of both species. Based on the LSU phylogeny, it is clear that strains of Sphaeropsis visci reside in this clade (CBS 186.97, 100163). Furthermore, our data also reveal that the strains deposited in CBS under the name L. theobromae represent several distinct species with this typical conidial ornamentation; the LSU phylogenetic data could not resolve the Lasiodiplodia/Diplodia clade. Lasiodiplodia gonubiensis and three new species of Lasiodiplodia recently described (Burgess et al., unpubl. data), were interspersed among species of Diplodia. The rather atypical Diplodia species recently described by Van Niekerk et al. (2004) as D. porosum Van Niekerk & Crous, also clustered in this clade. Botryosphaeria subglobosa (C. Booth) Arx & E. Müll. is another interesting example, as it has an anamorph described as Sphaeropsis subglobosa C. Booth. Although the latter species is illustrated to have what appears to be a germ slit in its aseptate conidia (Punithalingam 1969, De Hoog et al. 2000), conidia of CBS 448.91 were found to be hyaline, thick-walled, and to become pigmented with age. Mature conidia were observed to have more than one "germ slit", actually appearing more like striations (Fig. 3). This observation suggests that if Diplodia and Lasiodiplodia are seen as separate genera, S. subglobosa would be better accommodated in the latter genus.
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Clade 2: Botryosphaeria (anamorph Fusicoccum)
Barber et al.
(2005) have recently shown that
species of Fusicoccum can have Dichomera Cooke synanamorphs.
Furthermore, two species of Dichomera, D. versiformis Z.Q. Yuan,
Wardlaw & C. Mohammed and D. eucalypti (G. Winter) B. Sutton also
cluster in Clade 6 with the majority of the "Fusicoccum"
species. Phillips et al.
(2005b) also reported that
conidia of Fusicoccum aesculi from olives can become pigmented,
ovoid, ellipsoid or fusiform, 1–2-septate, similar to those observed by
Barber et al. (2005)
for F. aesculi. Phillips et al.
(2005b) also revealed
Fusicoccum dalmaticum (Thüm.) Vanev is the same as
Camarosporium dalmaticum (Thüm.) Zachos & Tzav.-Klon., both
being later synonyms of F. aesculi. Sutton
(1980) stated that
Camarosporium Schulzer was the pycnidial analogue of
Dichomera, which had more stromatic conidiomata. Given our current
knowledge of the phylogenetic value of conidiomatal structure in the
Dothideomycetes, it seems redundant to separate these anamorph genera
based on this character alone (also see illustrations in
Sutton 1980). The generic name
Camarosporium (1870) is older, and thus has preference over
Dichomera (1876). When a strain identified as D. saubinetii
(Mont.) Cooke (CBS
990.70; sterile, morphology unconfirmed) was subjected to sequence
analysis, it clustered in Clade 2, while strains identified as C.
quaternatum (CBS
134.97,
483.95; fertile,
matching the original description) clustered outside of the
Botryosphaeriaceae. In Fusicoccum s.str. (F.
aesculi) conidia are fusiform to ellipsoid, and with age become septate
and brown, to some extent appearing Dichomera-like. Whether strains
matching D. saubinetii in morphology will cluster in Clade 2 remains
to be determined.
Sutton (1980) stated that Macrophomopsis coronillae was closely related to F. aesculi, but distinguishable by its annellidic conidiogenous cells. Crous & Palm (1999) showed that percurrent proliferation occurred in the type of F. aesculi, and concluded that Pennycook & Samuels (1985) were probably correct to reduce M. coronillae to synonymy with F. aesculi. As shown in the current study, an isolate of M. coronillae (CBS 769.71) was indistinguishable from F. aesculi based on sequence data. However, this isolate produced pycnidial paraphyses in culture, which had not been observed on the type specimen of F. aesculi (Sutton 1980). Phillips (2000) used this feature to distinguish F. populi A.J.L. Phillips from F. aesculi. DNA sequence comparisons revealed, that this feature is uninformative at the species level (F. aesculi = F. populi), and that not all strains of F. aesculi form paraphyses. Furthermore, some pycnidia in the culture CBS 769.71 produced numerous paraphyses, while they were almost completely absent in others. A note by H.A. van der Aa in the CBS database mentions the fact that this isolate had also formed microconidia when it was first collected.
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Clade 3: Macrophomina (teleomorph unknown)
The asexual, sterile basidiomycete genus Rhizoctonia DC. has been
linked to a number of teleomorphs in different families, namely the
Platygloeaceae, Exidiaceae, Tulasnellaceae, Ceratobasidiaceae, etc.
(Stalpers & Andersen
1996). The reason these species are treated in the form-genus
Rhizoctonia, is that they are mostly sterile, and share the same
vegetative features typical of Rhizoctonia spp. Species have thus
been distinguished based on features such as sclerotium production, mycelial
colour, wide hyphae, all with two or several nuclei, length of cells, shape
and size of monilioid cells, and sclerotial size
(Parmeter & Whitney
1970).
Macrophomina phaseolina is the type species of the genus Macrophomina Petr., and is also the name given to the coelomycete synanamorph of Rhizoctonia bataticola (Taubenh.) E.J. Butler. The latter fungus is a root inhabitant, and has been implicated in numerous root rot diseases of a wide range of crops, commonly causing charcoal rot and ashy stem blight (Holliday & Punithalingam 1998). The name of the synanamorph, and its taxonomic placement, has been the topic of much controversy. In their IMI description sheet of the fungus, Holliday & Punithalingam (1988) mention that the conidiophores are hyaline phialides, short obpyriform to cylindrical, 5–13 x 4–6 µm. Conidia are described as being hyaline, ellipsoid to obovoid, 14–30 x 5–10 µm. Von Arx (1981) introduced the name Tiarosporella phaseolina (Tassi) van der Aa for this fungus, and also reduced the genus Macrophomina to synonymy under Tiarosporella Höhn. As no explanation was given, this treatment has largely been ignored by the plant pathological and mycological community, though von Arx (1987) retained it. The genus Tiarosporella [based on T. paludosa (Sacc. & Fiori ex P. Syd.) Höhn.] is characterised by having conidia formed from smooth, hyaline conidiogenous cells that lack periclinal thickenings and percurrent proliferations, and hyaline, subcylindrical to fusiform conidia that have irregular apical mucoid appendages (Nag Raj 1993). H.A. van der Aa (pers. comm.) informed the first author that the decision was based upon the fact that he had succeeded to induce sporulation of M. phaseolina in culture, and observed that the conidia have apical mucoid appendages, which prompted von Arx to place this fungus in Tiarosporella. In the present study we have been able to induce numerous strains of M. phaseolina to sporulate on sterile pine needles, and found that conidia form apical mucoid appendages (Figs 5, 6) as previously suggested by van der Aa. As this is inconsistent with the description provided by Holliday & Punithaligham (1988), we provide an emended description below:
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Basionym: Macrophoma phaseolina Tassi, Bull. Lab. Ort bot. Siena IV: 9. 1901.
Additional synonyms listed by Holliday & Punithalingam (1988).
Sclerotia occurring in host tissue or in soil, black, smooth, hard, 100–1000 µm diam. Conidiomata pycnidial, dark brown to black, solitary or gregarious, up to 200 µm diam, opening by a central ostiole; wall multilayered, cells dark brown, thick-walled. Conidiogenous cells lining the inner surface of the conidioma, hyaline, short obpyriform to subcylindrical, proliferating several times percurrently near the apex, 6–12 x 4–6 µm; young condiogenous cells covered by a mucous layer that extends over the apex of the developing conidium. Conidia ellipsoid to obovoid, (16–)20–24(–32) x (6–) 7–9(–11) µm; immature conidia hyaline, enclosed in a mucous sheath, that upon dehiscence encloses the top half of the conidium, transformed into two lateral tentaculiform, apical mucoid appendages (type C, Nag Raj 1993); mature conidia becoming medium to dark brown, with a granular outer layer that in some cases appears pitted, without any mucoid appendages; conidial hilum frequently with a marginal frill.
Notes: Although Macrophomina phaseolina can have conidia with apical mucoid appendages as found in Tiarosporella (Sutton & Marasas 1976), it is distinguished by having percurrently proliferating conidiogenous cells [not seen in any species of Tiarosporella sensu Nag Rag (1993), nor in those investigated here], and conidia that become dark brown at maturity. Based on these differences (and in the absence of authentic cultures of T. paludosa), the genus Macrophomina and the name M. phaseolina is retained. The three species of Tiarosporella that were available for this study clustered in Clade 1 (Figs 7, 8), suggesting that the latter clade is still unresolved.
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Clade 4: Neoscytalidium dimidiatum (teleomorph unknown)
Several distinct Fusicoccum-like fungi with conidia that become
septate with a darker central cell have been treated under the epithet
"mangiferae". Some isolates, however, formed a
Scytalidium-like synanamorph, while others did not.
Dothiorella mangiferae Syd. & P. Syd. was originally described from mango (Sydow et al. 1916). Nattrass (1933) described a similar fungus from pome and stone fruit trees, but noticed a pigmented conidial state, which led him to describe Hendersonula toruloidea Nattrass. Sutton & Dyko (1989) revised the genus Hendersonula Speg. and synonymised both D. mangiferae and H. toruloidea under the redescribed Nattrassia mangiferae (Syd. & P. Syd.) B. Sutton & Dyko. Furthermore, the mycelial synanamorph was described as Scytalidium dimidiatum (Penz.) B. Sutton & Dyko. Farr et al. (2005) made the point that the oldest name for the fungus was Torula dimidiata Penz., and hence introduced the combination Fusicoccum dimidiatum (Penz.) D.F. Farr, stating that the type species of the genera Nattrassia and Scytalidium were synonyms of F. dimidiatum. As seen in the present study, this fungus, with its powdery disarticulating aerial mycelium, is a genus in its own right within the Botryosphaeriaceae. Furthermore, the ex-type strain of Scytalidium, S. lignicola Pesante, (CBS 233.57) clusters outside the Botryosphaeriaceae (results not given), and hence Scytalidium is unavailable for this fungus.
Fusicoccum mangiferae (Syd. & P. Syd.) Johnson, Slippers &
M.J. Wingf. (
D. mangiferae, N. mangiferae)
is a distinct taxon (see Clade 6, Neofusicoccum) that should not be
confused with F. dimidiatum. When Sutton & Dyko
(1989) and Johnson
(1992) re-examined the type of
D. mangiferae, they did not observe the Scytalidium-like
anamorph on the type specimen, in accordance with Sydow et al.
(1916). Slippers et
al. (2005) studied
isolates identified as D. mangiferae (= N. mangiferae) from
mango in Australia, and found them to belong to Fusicoccum, for which
they introduced the name F. mangiferae (now Neofusicoccum,
Clade 6). They also did not observe the Scytalidium-like synanamorph
as described by Sutton & Dyko
(1989). The synonymy of H.
toruloidea (which has a Scytalidium-like synanamorph) with
F. mangiferae (which does not appear to have a
Scytalidium-like synanamorph), is thus rejected here. A new genus is
proposed to accommodate this fungus.
Neoscytalidium Crous & Slippers, gen. nov. MycoBank MB500868.
Genus anamorphosis hyphomyceticum. Arthroconidia catenata in mycelio aerio, pulverulenta, disarticulantia, cylindrica-truncata, oblongo-obtusa vel doliiformia, fusca, crassitunicata, 0–2-septata.
Conidia occurring in arthric chains in aerial mycelium, powdery to the touch, disarticulating, cylindrical–truncate, oblong–obtuse to doliiform, dark brown, thick-walled, 0–2-septate.
Type species: Neoscytalidium dimidiatum (Penz.) Crous & Slippers, comb. nov.
Neoscytalidium dimidiatum (Penz.) Crous & Slippers, comb. nov. MycoBank MB500869. Fig. 9.
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Scytalidium dimidiatum (Penz.) B. Sutton & Dyko,
Mycol. Res. 93: 484. 1989. Fusicoccum dimidiatum (Penz.) D.F. Farr, Mycologia 97:
740. 2005.
Clade 5: Dothidotthia (anamorph Dothiorella)
Concepts defining morphological features of Botryosphaeria
(ascomata, asci and hamathecium) have developed slowly
(Denman et al. 2000).
This has resulted in confusion between Botryosphaeria and
superficially similar genera such as Physalospora Niessl. and
Guignardia (von Arx &
Müller 1954, Hanlin
1990), Auerswaldiella Theiss. & Syd.,
Discochora Höhn., Dothidotthia Höhn.,
Neodeightonia C. Booth, Homostegia Fuckel and
Otthia Nitschke. Subsequent to the review of Denman et al.
(2000), two of these genera,
namely Otthia and Dothidotthia, have been variously treated,
and they are discussed here.
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In the phylogenetic analysis of DNA sequence data of the ITS region and EF
1- gene, Phillips et al.
(2005a) demonstrated that the
"Botryosphaeria" species with pigmented, septate
ascospores and Diplodia-like anamorphs formed a separate clade.
Dothiorella had been reduced to synonymy under Diplodia by
Crous & Palm (1999), who
did not have access to cultures and DNA sequence data and thus used a wider
morphological concept for Diplodia. Phillips et al.
(2005a) re-examined the type
of Dothiorella pyrenophora Sacc. (K 54912)
(Fig. 10), and stated that it
differs from Diplodia by having conidia that are brown and 1-septate
early in their development, while they are still attached to the conidiogenous
cells. In Diplodia (D. mutila), conidial darkening and
septation takes place after discharge. We have re-examined the types of both
genera in the present study, and concur with Phillips et al.
(2005a) that the genera have
distinct conidial characeristics. Teleomorphs of Dothiorella have
pigmented, septate ascospores, for which the genus Dothidotthia is
available. The latter genus had been recognised as a member of the
Botryosphaeriaceae by Barr
(1987,
1989), and is known to have
Diplodia-like anamorphs, which are now accommodated in
Dothiorella. The new taxa described by Phillips et al.
(2005a) must thus be placed in
Dothidotthia. These taxa will be treated elsewhere (A.J.L. Phillips,
in prep.).
Clade 6: Neofusicoccum (teleomorph Botryosphaeria-like)
An interesting issue to resolve is the morphological distinction between
the two larger Fusicoccum clades, namely Fusicoccum s.str.
(based on F. aesculi, and linked to the name
Botryosphaeria), and the larger Fusicoccum-like clade
(linked to Botryosphaeria-like teleomorphs), which includes most of
the species that are currently known from DNA sequence data. Although the
teleomorphs are similar in both clades, their anamorphs provide some clues for
a possible separation. There is little to choose in their Fusicoccum
anamorphs, but as seen in Saccharata, the distinguishing feature is
to be found in their synanamorphs. In Fusicoccum s. str. (F.
aesculi) conidia are fusiform to ellipsoid, and with age turn septate and
brown. In the Fusicoccum-like clade, two distinct conidial types are
seen, namely the first with a Fusicoccum-like morphology, which can
turn brown and septate with age (as seen in Clade 2). The second conidial form
has globose to pyriform conidia, which are brown, slightly verruculose, and
muriformly septate. It is debatable if Fusicoccum s.str. (Clade 2)
forms a distinct synanamorph. The synanamorph observed in the
Fusicoccum-like clade (Clade 6) cannot be accommodated in
Camarosporium (the stromatic analogue of Dichomera), as the
type species of Camarosporium, C. quaternatum
(CBS 134.97,
483.95) clusters
outside the Botryosphaeriaceae. As far as we could establish,
however, no genus is presently available for this clade, and thus a new one is
proposed below. We introduce a single generic name, namely for the anamorph
(which occurs with a Dichomera-like synanamorph), which is the more
informative morphological state:
Neofusicoccum Crous, Slippers & A.J.L. Phillips, gen. nov. MycoBank MB500870.
Teleomorph: Botryosphaeria-like
Synanamorph: Dichomera-like
Genus anamorphosis coelomyceticum. Fusicocco simile sed synanamorphe Dichomerae simili et conidiis brunneis, globosis vel pyriformibus, distinguendum.
Resembling species of Fusicoccum, but distinct in forming a Dichomera-like synanamorph with brown, globose to pyriform conidia.
Type species: Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, comb. nov.
Most species that have thus far been described in Fusicoccum appear to reside in this clade, as can be seen in the present, as well as other recent studies. To facilitate clarity, new combinations are proposed for those known to us from culture:
Neofusicoccum andinum (Mohali, Slippers & M.J. Wingf.) Mohali, Slippers & M.J. Wingf. comb. nov. MycoBank MB500871.
Basionym: Fusicoccum andinum Mohali, Slippers & M.J. Wingf., Mycol. Res. 10: 408. 2006.
Neofusicoccum arbuti (D.F. Farr & M. Elliott) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500872.
Basionym: Fusicoccum arbuti D.F. Farr & M. Elliott, Mycologia 97: 731. 2005.
Neofusicoccum australe(Slippers, Crous & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500873.
Basionym: Fusicoccum australe Slippers, Crous & M.J. Wingf., Mycologia 96: 1035. 2004.
Teleomorph: "Botryosphaeria" australis Slippers, Crous & M.J. Wingf., Mycologia 96: 1035. 2004.
Neofusicoccum eucalypticola (Slippers, Crous & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500874.
Basionym: Fusicoccum eucalypticola Slippers, Crous & M.J. Wingf., Stud. Mycol. 50: 351. 2005.
Teleomorph: "Botryosphaeria" eucalypticola Slippers, Crous & M.J. Wingf., Stud. Mycol. 50: 351. 2005.
Neofusicoccum eucalyptorum (Crous, H. Sm. ter & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500875.
Basionym: Fusicoccum eucalyptorum Crous, H. Sm. ter & M.J. Wingf., Mycologia 93: 280. 2001.
Teleomorph: "Botryosphaeria" eucalyptorum Crous, H. Sm. ter & M.J. Wingf., Mycologia 93: 280. 1998.
Neofusicoccum luteum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500876.
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Teleomorph: "Botryosphaeria" lutea Phillips, Sydowia 54: 59. 2002.
Neofusicoccum macroclavatum (Burgess, Barber & Hardy) Burgess, Barber & Hardy, comb. nov. MycoBank MB500877.
Basionym: Fusicoccum macroclavatum Burgess, Barber & Hardy, Austral. Pl. Pathol. 34: 562. 2005.
Note: For further information about this recently published species, see Burgess et al. (2005).
Neofusicoccum mangiferae (Syd. & P. Syd.) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500878.
Basionym: Dothiorella mangiferae Syd. & P. Syd., Ann. Mycol. 14: 192. 1916.
Nattrassia mangiferae (Syd. & P. Syd.) B. Sutton &
Dyko, Mycol. Res. 93: 484. 1989. Fusicoccum mangiferae (Syd. & P. Syd.) Johnson,
Slippers & M.J. Wingf., Mycologia 97: 106. 2005. Teleomorph: "Botryosphaeria" sp.
Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500879.
Basionym: Fusicoccum parvum Pennycook & Samuels, Mycotaxon 24: 455. 1985.
Teleomorph: "Botryosphaeria" parva Pennycook & Samuels, Mycotaxon 24: 455. 1985.
Neofusicoccum protearum(Denman & Crous) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500880.
Basionym: Fusicoccum protearum Denman & Crous, Mycologia 95: 301. 2003.
Teleomorph:"Botryosphaeria" protearum Denman & Crous, Mycologia 95: 301. 2003.
Neofusicoccum ribis (Slippers, Crous & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500881.
Basionym: Fusicoccum ribis Slippers, Crous & M.J. Wingf., Mycologia 96: 96. 2004.
Teleomorph: "Botryosphaeria" ribis Grossenb. & Duggar, Tech. Bull. N.Y. Agric. Exp. St. 18: 128. 1911.
Neofusicoccum viticlavatum (Niekerk & Crous) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500882.
Basionym: Fusicoccum viticlavatum Niekerk & Crous, Mycologia 96: 792. 2004.
Neofusicoccum vitifusiforme (Niekerk & Crous) Crous, Slippers & A.J.L. Phillips, comb. nov. MycoBank MB500883.
Basionym: Fusicoccum vitifusiforme Niekerk & Crous, Mycologia 96: 793. 2004.
Clade 7: "Fusicoccum" stromaticum (teleomorph unknown)
"Fusicoccum" stromaticum Mohali, Slippers
& M. J. Wingf. (Mohali et al.
2006) was described for a new Fusicoccum-like species
occurring on Eucalyptus and Acacia spp. in Venezuela. The
taxon was distinguished from other species of Fusicoccum based on its
unusually large conidiomata, the ability to grow at 35 °C, and
thick-walled conidia. Strains of this species have conidia that are encased in
a persistent mucous sheath, which is absent in other species of
Fusicoccum, and is the character that distinguishes it as genus from
Fusicoccum s.str.
Pseudofusicoccum Mohali, Slippers & M.J. Wingf. gen. nov. MycoBank MB500884.
Genus anamorphosis coelomyceticum. Fusicocco simile, sed conidiis strato mucido persistente circumdatis distinguendum.
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Type species: Pseudofusicoccum stromaticum (Mohali, Slippers & M.J. Wingf.) Mohali, Slippers & M. J. Wingf., comb. nov.
Pseudofusicoccum stromaticum (Mohali, Slippers & M.J. Wingf.) Mohali, Slippers & M.J. Wingf., comb. nov. MycoBank MB500885. Fig. 11.
Basionym: Fusicoccum stromaticum Mohali, Slippers & M.J. Wingf., Mycol. Res. 110: 408. 2006.
Clade 8: "Botryosphaeria" quercuum (anamorph Diplodia-like)
Von Arx & Müller
(1954) placed B.
melanops (Tul. & C. Tul.) G. Winter under B. quercuum
(Schwein.) Sacc., which is a complex in need of revision, including
Melanops tulasnei (Tul. & C. Tul.) Fuckel, the oldest generic
name available for this clade. To resolve the status of B. quercuum,
however, authentic cultures of all these names need to be studied, and linked
to existing names. The strain in Clade 8 closely matches the morphology of the
type specimen (Phillips et al., unpubl. data). No name is, however,
proposed for this genus pending the outcome of studies based on authentic
isolates.
Clade 9: Saccharata (anamorph Fusicoccum-like)
Wakefield (1922) described
an ascomycete associated with leaf spots and stem cankers of Protea
and Leucospermum species as Phyllachora proteae Wakef. This
latter fungus is characterised by having unilocular ascomata that develop
under a very small epidermal clypeus, cylindrical asci, pseudoparaphyses, and
hyaline, aseptate, ellipsoidal ascospores. Doidge
(1942) found the ascomatal
walls are continuous with, and similar in structure to the clypeus, and stated
that the fungus should be allocated elsewhere, possibly in
Botryosphaeria. Denman et al.
(1999) recollected this
species, placed it in Botryosphaeria, and also established a cultural
link with its anamorph, "Fusicoccum" proteae
Denman & Crous, which also forms a Diplodia-like synanamorph in
culture. On the basis of ITS DNA sequence comparisons, Denman et al.
(2000) later showed that the
fungus clustered outside the Botryosphaeria clades that accommodated
Fusicoccum and Diplodia anamorphs. Given its unilocular
ascomata, the presence of a clypeus, and its unusual Fusicoccum- and
Diplodia-like synanamorphs, Crous et al.
(2004) established a new
genus, Saccharata Denman & Crous to accommodate S.
proteae (Wakef.) Denman & Crous. The LSU phylogenies in this study
supports Saccharata as a distinct genus that is basal to, but
probably outside the Botryosphaeriaceae.
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Clade 11: Camarosporium and relatives
Several morphologically discordant taxa group in this clade, including
C. quaternatum, the type species of Camarosporium
(Fig. 12), but also an
unidentified Dothiorella-like strain (1-septate, brown conidia), and
another seen as an atypical Phyllosticta, namely P.
flevolandica (hyaline, 0–1-septate conidia)
(Van der Aa 1973). Other taxa
include Karstenula Speg. (anamorph Microdiplodia Tassi),
Letendraea Sacc. (Tubeufiaceae?), and Byssothecium
Fuckel (anamorph Chaetophoma-like). It appears that the
Dothiorella-like strain (CPC 12268) is, in fact, a species of
Microdiplodia. Sutton
(1977) reported that the genus
was introduced for stem- or branch-inhabiting species with small, brown,
1-septate conidia. This is consistent with the results of this study where the
strain examined was isolated from branches of Sophora chrysophylla
collected in Hawaii. As we have shown here that the genus
Microdiplodia Tassi could be used for these small-spored
Dothiorella-like species, the genus needs to be lectotypified
according to Tassi's original concept (see
Sutton 1977).
Clade 12: Stenocarpella (teleomorph unknown)
The genus Stenocarpella Syd. & P. Syd. is based on S.
macrospora (Earle) B. Sutton. The genus contains two species that cause
Diplodia ear rot of maize, namely S. macrospora and S.
maydis (Berk.) B. Sutton. These taxa were formerly treated in
Diplodia by Sutton
(1964), and
Macrodiplodia Sacc. by Petrak & Sydow
(1927). Sutton
(1964,
1980) was of the opinion that
these species should be accommodated in a genus other than Diplodia,
and because the status of Macrodiplodia was unknown, he placed them
in Stenocarpella (Sutton
1977). This treatment has not been widely accepted, and plant
pathologists refer to "Diplodia ear rot", and continue to use the
Diplodia names.
Because cultures were not available for S. maydis and S. macrospora, these two species were recollected as part of the present study, and subjected to DNA sequence comparisions. Interestingly, they clustered in the Diaporthales, clearly supporting the decision by Sutton (1964, 1980) to move them to their own genus, Stenocarpella. Species of Diplodia are quite variable in morphology, and hence it is difficult to see immediately which morphological features separate Stenocarpella from Diplodia. Species of Stenocarpella tend to have unilocular, thick-walled pycnidia with walls of brown textura angularis. Under moist conditions, they exude a long cirrhus of brown conidia via a central ostiole (reminiscent of Phaeophleospora Rangel). Conidiogenous cells are phialidic, thin-walled and hyaline, but also proliferating percurrently. Conidia are septate, brown, smooth, thin-walled, subcylindrical to narrowly obclavate (Fig. 13), thus different from typical fusoid to ellipsoid, thick-walled conidia of Diplodia. To facilitate future research with these pathogens, epitype specimens and cultures are designated below:
Stenocarpella maydis (Berk.) B. Sutton, in Sutton, The coelomycetes, fungi imperfecti with pycnidia, acervuli and stromata: 432. 1980.
Basionym: Sphaeria maydis Berk., Hooker's J. Bot. London 6: 15. 1847.
Additional synonyms listed in Sutton (1980).
Types: U.S.A., Salem, Bethlehem, Zea mays, Schweinitz, 1832, IMI 96546 isotype. South Africa, KwaZulu-Natal, Simdlangentsha, Bt Zea mays hybrid from 2003-04 season, J. Rheeder, epitype designated here, CBS 117558, preserved as freeze-dried inactive strain (= MRC 8613); ibid. CBS 117557 = MRC 8612; Hlabisa, commercial hybrid PAN-6043, MRC 8614 = CBS 117559.
Stenocarpella macrospora (Earle) B. Sutton, Mycol. Pap. 141: 202. 1977. Fig. 13.
Basionym: Diplodia macrospora Earle, Bull. Torrey Bot. Cl. 24: 29. 1897.
Additional synonyms in Sutton (1980).
Types: U.S.A., Alabama, Auburn, Lee Co., F.S. Earle, 1896, IMI 12790, isotype. South Africa, KwaZulu-Natal, Hlabisa, rain damaged Bt Zea mays hybrid, 2003-04 season, J. Rheeder, epitype designated here, CBS 117560, preserved as freeze-dried inactive strain (= MRC 8615).
This study provides a framework to align the taxonomy of the Botryosphaeriaceae with the phylogenetic lineages within the group. It also highlights the previously unrealised morphological and evolutionary complexity of the group. Specific studies are now needed to clarify some remaining, and arising, taxonomic and phylogenetic questions within this family. To resolve remaining taxonomic uncertainties, epitypes of key species, representing the oldest names in the respective groups, will need to be collected, studied and designated. To resolve the phylogenetic uncertainties (e.g. Clade 1 and B. mamane) sequences for additional gene regions (to add more informative sites, and from unlinked loci) will have to be added. Specific studies focussing on the phylogenies within the clades, and expanding on the current set of available cultures (e.g. Clades 1, 10 and 11), will add valuable information on the evolution within these groups, and also help identify definitive morphological characters.
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Acknowledgments |
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References |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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