While the taxonomy and pathology of Botryosphaeria and Neofusicoccum has been studied intensively, Diplodia has several taxonomic problems that need to be resolved. This genus contains well-known plant pathogens including D. pinea (blight on pine trees), D. corticola (canker and dieback of cork oak) and D. mutila and D. seriata, which occur on a wide range of hosts. This suggests that these two species may in fact represent species complexes. The aim of this work was to resolve these cryptic species complexes - species that are morphologically indistinguishable and can be only separated at the phylogenetic level. Isolates were characterized on the basis of their micromorphology, including conidial dimensions, shape, pigmentation and septation, colony morphology and mycelial growth rate. Phylogenetic relationships were determined, firstly by microsatellite fingerprinting and then through analysis of ITS nucleotide sequences, supplemented with partial sequences of the translation elongation factor 1-α and β-tubulin genes. By integrating morphological characters with phylogenetic data several species were resolved within the Diplodia mutila complex, two new species (D. bulgarica and D. intermedia) were described, the status of D. fraxini and D. malorum was clarified and it was revealed that the D. pinea group may also be a complex of species.

Mestrado em Engenharia Agronómica - Instituto Superior de Agronomia