To expand our knowledge of Fusarium head blight (FHB) pathogen and trichothecene toxin diversity, a global collection of 2100 isolates was screened for novel genetic variation, resulting in the identification of 16 phylogenetically divergent FHB isolates. The affinities and taxonomic status of these novel isolates were evaluated via phylogenetic analyses of multilocus DNA sequence data (13 genes; 16.3 kb/strain) together with analyses of their morphology, pathogenicity to wheat, and trichothecene toxin potential. Based on the results of these analyses, we formally describe two novel species (Fusarium vorosii and Fusarium gerlachii) within the Fusarium graminearum species complex (Fg complex), and provide the first published report of Fg complex isolates with either a nivalenol or 3-acetyldeoxynivalenol chemotype within the U.S. In addition, we describe a highly divergent population of F. graminearum from the Gulf Coast of the U.S., and divergent isolates of F. acaciae-mearnsii from Australia and South Africa.
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