A phylogenetic redefinition of anamorph genera in Mycosphaerella based on ITS rDNA sequence and morphology
Anamorph genera associated with Mycosphaerella are separated on a combination of characters such as conidiomatal structure, the nature and arrangement of conidiophores, conidiogenesis, dehiscence scars and pigmentation. To date 27 genera have been reported as anamorphs of Mycosphaerella, 19 of which were included in this study. Based on the phylogeny of the ITS1, 5.8S, and ITS2 rDNA sequence data, Mycosphaerella proved to be monophyletic. The major group consisted of several small clusters correlating to specific anamorph genera, as well as other clusters containing an assemblage of anamorph genera. Although Mycosphaerella is monophyletic, it appears that many of the morphological characters defining different anamorph genera evolved more than once and for the most part do not represent true groups within Mycosphaerella. Nevertheless, the anamorph generic concepts contain valuable information of practical use to plant pathologists and mycologists working with these organisms. Based on these results, as well as a re-evaluation of the criteria upon which anamorph genera are distinguished in this complex, a reduced set of informative criteria and genera are proposed. The degree of scar thickening, darkening and refraction, as well as the presence or absence of pigmentation in conidiophores and conidia still appear to be useful features delimiting anamorph genera of Mycosphaerella.