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Unravelling Mycosphaerella: do you believe in genera?

Crous PW, Summerell BA, Carnegie AJ, Wingfield MJ, Hunter GC, Burgess TI, Andjic V, Barber PA, Groenewald JZ - Persoonia (2009)

Bottom Line: The genus Schizothyrium with Zygophiala anamorphs is supported as belonging to the Schizothyriaceae, while Dissoconium and Ramichloridium appear to represent a distinct family.Several clades remain unresolved due to limited sampling.Mycosphaerella, which has hitherto been used as a term of convenience to describe ascomycetes with solitary ascomata, bitunicate asci and 1-septate ascospores, represents numerous genera and several families yet to be defined in future studies.

View Article: PubMed Central - PubMed

Affiliation: CBS-KNAW Fungal Biodiversity Centre, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands;

ABSTRACT
Many fungal genera have been defined based on single characters considered to be informative at the generic level. In addition, many unrelated taxa have been aggregated in genera because they shared apparently similar morphological characters arising from adaptation to similar niches and convergent evolution. This problem is aptly illustrated in Mycosphaerella. In its broadest definition, this genus of mainly leaf infecting fungi incorporates more than 30 form genera that share similar phenotypic characters mostly associated with structures produced on plant tissue or in culture. DNA sequence data derived from the LSU gene in the present study distinguish several clades and families in what has hitherto been considered to represent the Mycosphaerellaceae. In some cases, these clades represent recognisable monophyletic lineages linked to well circumscribed anamorphs. This association is complicated, however, by the fact that morphologically similar form genera are scattered throughout the order (Capnodiales), and for some species more than one morph is expressed depending on cultural conditions and media employed for cultivation. The present study shows that Mycosphaerella s.s. should best be limited to taxa with Ramularia anamorphs, with other well defined clades in the Mycosphaerellaceae representing Cercospora, Cercosporella, Dothistroma, Lecanosticta, Phaeophleospora, Polythrincium, Pseudocercospora, Ramulispora, Septoria and Sonderhenia. The genus Teratosphaeria accommodates taxa with Kirramyces anamorphs, while other clades supported in the Teratosphaeriaceae include Baudoinea, Capnobotryella, Devriesia, Penidiella, Phaeothecoidea, Readeriella, Staninwardia and Stenella. The genus Schizothyrium with Zygophiala anamorphs is supported as belonging to the Schizothyriaceae, while Dissoconium and Ramichloridium appear to represent a distinct family. Several clades remain unresolved due to limited sampling. Mycosphaerella, which has hitherto been used as a term of convenience to describe ascomycetes with solitary ascomata, bitunicate asci and 1-septate ascospores, represents numerous genera and several families yet to be defined in future studies.

No MeSH data available.


(five parts) Maximum likelihood tree from RAxML showing the phylogenetic relationships based on the LSU sequence alignment. The scale bar shows 5 substitutions per site, and bootstrap support values (> 69 %) from 1 000 replicates are shown at the nodes. Ex-type sequences are printed in bold face. The tree was rooted to Phaeobotryosphaeria visci (GenBank accession DQ377868).
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Figure 1: (five parts) Maximum likelihood tree from RAxML showing the phylogenetic relationships based on the LSU sequence alignment. The scale bar shows 5 substitutions per site, and bootstrap support values (> 69 %) from 1 000 replicates are shown at the nodes. Ex-type sequences are printed in bold face. The tree was rooted to Phaeobotryosphaeria visci (GenBank accession DQ377868).

Mentions: The manually adjusted LSU alignment contained 316 taxa (including the outgroup sequence) and 773 characters were included in the phylogenetic analysis. As the focus of this paper was the higher-order phylogeny of these fungi, the ITS sequences obtained were not used in the phylogenetic analyses. They were, however, used in a follow-up study on species (Crous et al. 2009c) and lodged in GenBank as part of that study, if not present there already. The three distance analyses yielded trees with identical overall topologies and supported the same lineages as the RAxML phylogeny but with some rearrangements of lineages at the deeper nodes (data not shown). Examples of these rearrangements include the swapping of Clade 18 (Dissoconium) and Clade 19 (Schizothyrium) from the Teratosphaeriaceae to the Mycosphaerellaceae compared to the RAxML phylogeny, highlighting the insecure phylogenetic position of these two genera. No significant increase or decrease in bootstrap support values was observed between the distance and RAxML analyses and the low bootstrap support values observed for some clades (see below) could be due to the choice of gene and/or the sampling for the analyses. The obtained RAxML phylogeny with a tree length of 2 357 547 is shown in Fig. 1. The final ML optimisation likelihood value obtained was −9197.49319 and the alpha value was estimated as 0.236078.


Unravelling Mycosphaerella: do you believe in genera?

Crous PW, Summerell BA, Carnegie AJ, Wingfield MJ, Hunter GC, Burgess TI, Andjic V, Barber PA, Groenewald JZ - Persoonia (2009)

(five parts) Maximum likelihood tree from RAxML showing the phylogenetic relationships based on the LSU sequence alignment. The scale bar shows 5 substitutions per site, and bootstrap support values (> 69 %) from 1 000 replicates are shown at the nodes. Ex-type sequences are printed in bold face. The tree was rooted to Phaeobotryosphaeria visci (GenBank accession DQ377868).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2802725&req=5

Figure 1: (five parts) Maximum likelihood tree from RAxML showing the phylogenetic relationships based on the LSU sequence alignment. The scale bar shows 5 substitutions per site, and bootstrap support values (> 69 %) from 1 000 replicates are shown at the nodes. Ex-type sequences are printed in bold face. The tree was rooted to Phaeobotryosphaeria visci (GenBank accession DQ377868).
Mentions: The manually adjusted LSU alignment contained 316 taxa (including the outgroup sequence) and 773 characters were included in the phylogenetic analysis. As the focus of this paper was the higher-order phylogeny of these fungi, the ITS sequences obtained were not used in the phylogenetic analyses. They were, however, used in a follow-up study on species (Crous et al. 2009c) and lodged in GenBank as part of that study, if not present there already. The three distance analyses yielded trees with identical overall topologies and supported the same lineages as the RAxML phylogeny but with some rearrangements of lineages at the deeper nodes (data not shown). Examples of these rearrangements include the swapping of Clade 18 (Dissoconium) and Clade 19 (Schizothyrium) from the Teratosphaeriaceae to the Mycosphaerellaceae compared to the RAxML phylogeny, highlighting the insecure phylogenetic position of these two genera. No significant increase or decrease in bootstrap support values was observed between the distance and RAxML analyses and the low bootstrap support values observed for some clades (see below) could be due to the choice of gene and/or the sampling for the analyses. The obtained RAxML phylogeny with a tree length of 2 357 547 is shown in Fig. 1. The final ML optimisation likelihood value obtained was −9197.49319 and the alpha value was estimated as 0.236078.

Bottom Line: The genus Schizothyrium with Zygophiala anamorphs is supported as belonging to the Schizothyriaceae, while Dissoconium and Ramichloridium appear to represent a distinct family.Several clades remain unresolved due to limited sampling.Mycosphaerella, which has hitherto been used as a term of convenience to describe ascomycetes with solitary ascomata, bitunicate asci and 1-septate ascospores, represents numerous genera and several families yet to be defined in future studies.

View Article: PubMed Central - PubMed

Affiliation: CBS-KNAW Fungal Biodiversity Centre, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands;

ABSTRACT
Many fungal genera have been defined based on single characters considered to be informative at the generic level. In addition, many unrelated taxa have been aggregated in genera because they shared apparently similar morphological characters arising from adaptation to similar niches and convergent evolution. This problem is aptly illustrated in Mycosphaerella. In its broadest definition, this genus of mainly leaf infecting fungi incorporates more than 30 form genera that share similar phenotypic characters mostly associated with structures produced on plant tissue or in culture. DNA sequence data derived from the LSU gene in the present study distinguish several clades and families in what has hitherto been considered to represent the Mycosphaerellaceae. In some cases, these clades represent recognisable monophyletic lineages linked to well circumscribed anamorphs. This association is complicated, however, by the fact that morphologically similar form genera are scattered throughout the order (Capnodiales), and for some species more than one morph is expressed depending on cultural conditions and media employed for cultivation. The present study shows that Mycosphaerella s.s. should best be limited to taxa with Ramularia anamorphs, with other well defined clades in the Mycosphaerellaceae representing Cercospora, Cercosporella, Dothistroma, Lecanosticta, Phaeophleospora, Polythrincium, Pseudocercospora, Ramulispora, Septoria and Sonderhenia. The genus Teratosphaeria accommodates taxa with Kirramyces anamorphs, while other clades supported in the Teratosphaeriaceae include Baudoinea, Capnobotryella, Devriesia, Penidiella, Phaeothecoidea, Readeriella, Staninwardia and Stenella. The genus Schizothyrium with Zygophiala anamorphs is supported as belonging to the Schizothyriaceae, while Dissoconium and Ramichloridium appear to represent a distinct family. Several clades remain unresolved due to limited sampling. Mycosphaerella, which has hitherto been used as a term of convenience to describe ascomycetes with solitary ascomata, bitunicate asci and 1-septate ascospores, represents numerous genera and several families yet to be defined in future studies.

No MeSH data available.