Characterization of Fusarium strains recovered from wheat with symptoms of head blight in Kentucky

Authors: BEC, S - University Of Kentucky; Ward, Todd; FARMAN, M - University Of Kentucky; O Donnell, Kerry; HERSHMAN, D - University Of Kentucky; VAN SANFORD, D - University Of Kentucky; VAILLANCOURT, L - University Of Kentucky

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2014
Publication Date: 11/15/2015
Citation: Bec, S., Ward, T.J., Farman, M., O'Donnell, K., Hershman, D., Van Sanford, D., Vaillancourt, L.J. 2015. Characterization of Fusarium strains recovered from wheat with symptoms of head blight in Kentucky. Plant Disease. 99(11):1622-1632.

Interpretive Summary: Fungi within the Fusarium graminearum species complex (FGSC) are responsible for Fusarium head blight (FHB), an economically destructive disease of wheat, barley, and other cereals. In addition, these fungi contaminate grain with trichothecene mycotoxins that pose a significant threat to food safety and animal health. The U.S. population is diverse, and includes several genetically distinct local subpopulations, some of which are more aggressive towards wheat and produce greater amounts of toxin. In this study we used a variety of genetic tools to characterize the FHB pathogens found in Kentucky and Indiana, which is a transition zone between the Mid-Atlantic and Midwestern wheat production areas. Comparative genetic analysis indicated that the FHB population in Kentucky and Indiana belonged to the dominant North American population, and has not been significantly influenced by novel populations that have recently been described from other parts of the U.S. and Canada. However, the population in Kentucky and Indiana is diverse, with unique strain types found at each location, and multiple strains isolated from the same wheat head. These findings provide an important baseline for continued monitoring of population dynamics among FGSC strains causing FHB in Kentucky. A detailed understanding of the population structure, and timely detection of shifts in that population, will be valuable for breeding programs focused on developing wheat varieties with a broad and durable resistance to the targeted pathogen population.

Technical Abstract: Fusarium graminearum species complex (FGSC) members cause Fusarium head blight (FHB) of wheat (Triticum aestivum L.) and small grains in the United States. The U.S. population is diverse, and includes several genetically distinct local emergent subpopulations, some more aggressive and toxigenic than the majority population. Kentucky is a transition zone between the Mid-Atlantic and Midwestern wheat production areas. Sixty-eight Fusarium strains were isolated from symptomatic wheat heads from central and western Kentucky and southern Indiana in 2007. A multilocus genotyping assay and a variety of additional molecular markers, including some novel markers developed using the F. graminearum genome sequence, were used to characterize the pathogen population. Five of the isolates were identified as members of two non-FGSC species, F. acuminatum and F. cf. reticulatum, but they did not cause symptoms in greenhouse tests. All the FGSC isolates belonged to the 15-ADON chemotype of F. graminearum. Comparative genetic analysis using variable nuclear tandem repeat (VNTR) markers indicated that the population in Kentucky and Indiana belonged to the dominant North American population, with some diversification likely due to local evolution. Telomere and restriction fragment length polymorphism (RFLP) fingerprinting markers based on repetitive sequences revealed a high degree of genetic diversity within the population, with unique genotypes found at each location, and multiple genotypes isolated from the same head.