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United States Department of Agriculture

Agricultural Research Service

Title: Two Divergent Intragenomic Rdna Its2 Types Within a Monophyletic Lineage Ofthe Fungus Fusarium Are Nonorthologous

item O`donnell, Kerry
item Cigelnik, Elizabeth

Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Proceedings
Publication Acceptance Date: July 26, 1996
Publication Date: N/A

Interpretive Summary: Fusarium is a large genus of filamentous fungi whose members collectively represent the single most important fungal plant pathogen. Fusaria traditionally placed in the morphologically-defined Sections Liseola and Elegans represent some of the most important plant pathogens and they are noted for the production of a plethora of fungal toxins, including fumonisins and moniliformin. Traditional microbiological methods for the accurate identification of these agronomically important fungi are unavailable. In this study, we have used DNA evidence to develop objective methods for the early detection and rapid, identification of these toxigenic molds. Compared with the several weeks required using current microbiological procedures that involve considerable guess-work, our molecular-based identifications are 100% accurate and can be made within 24 hours.

Technical Abstract: The evolutionary history of the phytopathogenic Gibberella fujikuroi- complex of Fusarium and related species was elucidated by cladistic analysis of DNA sequences obtained from multiple unlinked loci. Gene phylogenies inferred from the mitochondrial small subunit (mtSSU) rDNA, nuclear large subunit (LSU) rDNA, and beta tubulin gene introns were concordant, providing strong support for a fully resolved phylogeny of all biological and most morphological species. Discordance of the nuclear rDNA internal transcribed spacer 2 (ITS2) gene tree indicates that it is not a species tree. Instead, phylogenetic reconstruction revealed that two divergent ITS2 types exhibit a stochastic pattern of lineage sorting within Fusarium, thus obscuring true sister group relationships. The results suggest that the ancestral ITS2 types may have been combined by interspecific hybridization.

Last Modified: 4/18/2015
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