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United States Department of Agriculture

Agricultural Research Service

Research Project: Molecular Approaches for Improved Cercospora Leaf Spot Control in Sugarbeet

Location: Sugarbeet and Potato Research

Title: Characterization of Fusarium secorum, a new species causing Fusarium yellowing decline of sugar beet in North Central USA

Authors
item Secore, Gary -
item Rivera-Varas, Viviana -
item Christ, Daniela -
item Mathew, Febina -
item Khan, Mohamed -
item Varrelmann, Mark -
item Bolton, Melvin

Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 3, 2014
Publication Date: N/A

Interpretive Summary: This manuscript formally describes and characterizes a new Fusarium species. The species was named Fusarium secorum and causes a disease named Fusarium yellowing decline on sugarbeet. Using a variety of methods, the pathogen was shown to be different than all other Fusarium species currently described. Fusarium secorum produces a single secondary metabolite called beauvericin. The fungus is the only known Fusarium species to produce circle-shaped hyphae that may bear microconidia as well as corkscrew-shaped hyphae. Fusarium yellowing decline is noted for early death in seedlings and half to full-leaf yellowing of leaves in adult plants.

Technical Abstract: This study characterized a novel sugar beet (Beta vulgaris L.) pathogen from the Red River Valley in north central USA, which was formally named Fusarium secorum. Molecular phylogenetic analyses of three loci (translation elongation factor1a, calmodulin, mitochondrial small subunit) and the morphological species recognition concept strongly supported the inclusion of F. secorum in the Gibberella fujikuroi species complex (GFSC). Phylogenetic analyses identified F. secorum as a sister taxon of F. acutatum and a member of the African subclade of the GFSC. Fusarium secorum can be distinguished from all other known species morphologically by the production of circinate hyphae that may produce microconidia and abundant corkscrew-shaped hyphae in culture. To assess mycotoxin production potential, 45 typical secondary metabolites were tested in F. secorum rice cultures, but only beauvericin was produced in detectable amounts by each isolate. Results of pathogenicity experiments revealed that F. secorum isolates are able to induce half- and full-leaf yellowing foliar symptoms and vascular necrosis in roots and petioles of sugar beet. Inoculation with F. acutatum did not result in any disease symptoms. The sugar beet disease caused by F. secorum is named Fusarium yellowing decline.

Last Modified: 7/25/2014
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