Submitted to: National American Phytopathology Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 7/31/1996
Publication Date: N/A
Technical Abstract: Phylogenetic relationships of the Gibberella fujikuroi and F. oxysporum species complexes of Fusarium were investigated by parsimony analysis of DNA sequences from multiple loci. Gene trees inferred from the beta-tubulin gene exons and introns, mitochondrial small subunit rDNA, and 5' portion of the nuclear 28S rDNA were largely concordant, and in a combined analysis, provide strong statistical support for an area cladogram corresponding to species radiations in America, Africa, and Asia within the G. fujikuroi complex. Africa is the most phylogenetically diverse area with 16 species, followed by America (12 species) and Asia (8 species). Discordance of the nuclear ribosomal internal transcribed spacer (ITS) based tree with gene trees from the other loci sequenced is due to paralogous or xenologous ITS2 loci. The molecular evidence suggests that the divergent ITS2 types were combined by an ancient interspecific hybridization or gene duplication that predates the evolutionary radiation of these fusaria. The results indicate that traditional sectional and species-level taxonomic schemes for these lineages are artificial and a more natural classification is proposed.