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United States Department of Agriculture

Agricultural Research Service

Title: Discordant Evolution of Trichothecene Toxins and Species Within the Fusarium Graminearum Species Complex: Phylogenetic Evidence from Multigene Genealogies

item O`donnell, Kerry
item Ward, Todd
item Kistler, H

Submitted to: International Fusarium Workshop
Publication Type: Abstract Only
Publication Acceptance Date: January 30, 2003
Publication Date: N/A

Technical Abstract: Fusarium head blight [FHB] or scab of small grain cereals today ranks as one of the most devastating plant diseases worldwide. These pathogens often contaminate seeds with trichothecene and estrogenic mycotoxins which can result in significant reduction in seed yields and quality. In order to understand the host range, geographic distribution and mycotoxin potential of the trichothecene producing fusaria, species limits are being investigated using a genealogical concordance version of the phylogenetic species. Results of these ongoing studies have revealed that the primary etiological agent of FHB, F. graminearum, actually consists of 9 biogeographically structured, reciprocally monophyletic cryptic species. A preliminary global molecular epidemiology survey has shown that at least 3 of these cryptic species are in Australia, and 2 of these are also in New Zealand. The evolutionary history of the trichothecene mycotoxin gene cluster was investigated to elucidate the discord between species limits and trichothecene chemotypes. Trans-specific polymorphism within these virulence-associated genes appears to have been maintained by balancing selection acting on chemotype differences that originated in the ancestor of this species complex. At least 5 of the species within this clade are still segregating for trichothecene chemotype. Keywords: Evolution, trichothecenes, phylogeny, species

Last Modified: 4/18/2015
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