Opening the Pandora's box called Mycosphaerella

Phytopathogenic fungi that are mycosphaerella-like in morphology (Capnodiales, Dothideomycetes) represent close to 50 genera that are distributed over several families, including Cladosporiaceae, Dissoconiaceae, Mycosphaerellaceae and Teratosphaeriaceae. These genera represent a range of nutritional modes, being either plant pathogenic, lichenized, saprobic, or parasitic on other fungi or animals. In the strict sense the genus Mycosphaerella only applies to species with Ramularia anamorphs. Well-known model organisms such as the Sigatoka leaf spot disease complex of bananas involves members of the genus Pseudocercospora, while the septoria leaf blotch complex of cereals involve members of Zymoseptoria. Not only are most of the genera in the Mycosphaerella complex poly- or paraphyletic, but most of the known pathogens actually represent complexes of cryptic taxa that vary in their geographic distributions. A further interesting phenomenon that is common to phytopathogenic species in the Capnodiales is the co-occurrence of different species from the same or different genera in a single leaf lesion or stem canker. This finding has important implications for trade in agricultural and forestry produce, as pathogens of different hosts can be introduced into new environments on non-host material, which they colonise as secondary organisms.