Submitted to: International Congress of Mycology Proceedings and Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/2/2002
Publication Date: N/A
Technical Abstract: Species of the filamentous fungal genus Fusarium collectively represent the most important group of toxigenic plant pathogens. DNA sequences of multiple, mostly single copy nuclear protein coding genes are being used to investigate species limits within Fusarium using a genealogical concordance version of the phylogenetic species concept [GCPSR; Taylor et al. 2000]. Knowledge of species boundaries within a phylogenetic framework is essential for understanding the evolution of mycotoxins, host range and biogeography of these mycotoxigenic phytopathogens. Application of GCPSR in Fusarium revealed that this genus contains at least 10 times more species than previously recognized using a morphological species concept [Nelson et al. 1983]. In addition, GCPSR has also proven to be a powerful method for identifying gene-gene discordances. This is important because gene tree-species tree problems have been encountered in all major lineages of Fusarium. Genealogical discordances are due to several diverse evolutionary processes, including transspecies evolution, introgressive hybridization and paralogy. A striking example of discordance is illustrated by the evolution of the trichothecene toxin gene cluster within the F. graminearum species complex. The evolutionary history of this gene cluster is highly discordant with species phylogenies inferred from genes outside the toxin gene cluster. Several examples of genealogical concordance and discordance will be presented.