Mycosphaerella
Mycosphaerella is a
The following introduction about the fungal genus Mycosphaerella is copied (with permission) from the dissertation of W. Quaedvlieg (named: Re-evaluating Mycosphaerella and allied genera).[1]
Species belonging to the fungal genus Mycosphaerella (1884) (Capnodiales, Dothideomycetes) have evolved as
The identification of Mycosphaerella species by morphological means is extremely difficult as these taxa produce very small fruiting structures with highly conserved morphologies, tending to grow and sporulate poorly in culture and for over 120 years, identification was based on morphology alone. These identification difficulties are amplified by the fact that up to six different species can inhabit the same lesion as either a primary or secondary pathogen, making even host-specific species difficult to identify. The introduction of affordable sequencing technology during the first decade of the 21st century allowed for much more accurate species delimitation and phylogenetic elucidation, leading to the conclusion that the broad taxonomic description of the genus Mycosphaerella and a lack of clear morphological features led to many Mycosphaerella and mycosphaerella-like species being misidentified. Because the classic taxonomic description of Mycosphaerella is broad and includes so many mycosphaerella-like species, the traditional generic concept of Mycosphaerella will hereafter be referred to as Mycosphaerella sensu lato (s. lat.) in order to avoid confusion.
Currently more than 3 000 species and close to 10 000 names are associated with Mycosphaerella s. lat., but work by Verkley et al. (2004) revealed that the genus Mycosphaerella s. str. (based on M. punctiformis) was in fact limited to species with Ramularia asexual morphs. Research by Braun (1990, 1998) showed that there are only about 500 Ramularia species known from literature, leaving the majority of mycosphaerella-like species that will need to be reclassified into taxonomically correct genera and families. Since the advent of mass sequencing technology, 39 taxonomically correct genera have already been confirmed as belonging to the Mycosphaerellaceae via molecular means:
(Amycosphaerella, Neopseudocercospora, Ramularia, Caryophylloseptoria, Neoseptoria, Ramulispora, Cercospora, Pallidocercospora, Ruptoseptoria, Cercosporella, Paracercospora, Scolecostigmina, Colletogloeum, Paramycosphaerella, Septoria, Cytostagonospora, Passalora*, Sonderhenia, Distocercospora, Periconiella, Sphaerulina, Dothistroma, Phaeophleospora, Stenella, Lecanosticta, Phloeospora, Stromatoseptoria, Microcyclosporella, Polyphialoseptoria, Trochophora, Neodeightoniella, Polythrincium, Xenomycosphaerella, Neomycosphaerella, Pseudocercospora, Zasmidium, Neopenidiella, Pseudocercosporella* and Zymoseptoria)
- The genera Passalora and Pseudocercosporella are known to be paraphyletic and will be treated separately in the near future.
Although at least 25 more genera with postulated Mycosphaerellaceae affinity have yet to be confirmed. The current generic and family concepts of both Mycosphaerella s. str., the Mycosphaerellaceae and the Teratosphaeriaceae have evolved indirectly from the work of Crous (1998), who used culture and asexual morphological characteristics to show that Mycosphaerella s. lat. was in fact polyphyletic, suggesting that it should be subdivided into natural genera as defined by its asexual morphs. In contrast to these findings, the first sequence-based phylogenetic trees published for Mycosphaerella s. lat. (based mainly on ITS
As such, the name Mycosphaerella should be limited to species with Ramularia sexual forms, but the name Ramularia actually predates the name Mycosphaerella, so the name Ramularia has preference over Mycosphaerella, and will be placed on the list of protected names.
Mating type
Three closely related Mycosphaerella species, M. fijiensis, M. musicola and M. eumusae cause a destructive disease of bananas. Each of these three species is heterothallic, that is, matings can only occur between individuals of different mating type. Although the mating type DNA sequences of the three species appear to have arisen from a common ancestral sequence, there also has been considerable evolutionary divergence between them.[2]
References
- hdl:1874/308485.
- ^ Arzanlou M, Crous PW, Zwiers LH. Evolutionary dynamics of mating-type loci of Mycosphaerella spp. occurring on banana. Eukaryot Cell. 2010 Jan;9(1):164-72. doi: 10.1128/EC.00194-09. Epub 2009 Nov 13. PMID 19915079