|Van Coller, Gert|
Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2011
Publication Date: 9/20/2011
Citation: Boutigney, A., Ward, T.J., Van Coller, G.J., Flett, B., Lamprecht, S.C., O Donnell, K., Viljoen, A. 2011. Analysis of the Fusarium graminearum species complex from wheat, barley, and maize in South Africa provides evidence of species-specific differences in host preference. Fungal Genetics and Biology. 48(9):914-920. Interpretive Summary: Fungi within the Fusarium graminearum species complex (FGSC) are responsible for economically destructive diseases of wheat, barley, and other cereals world-wide. In addition, these fungi contaminate grain with are trichothecene mycotoxins that pose a significant threat to food safety and animal health. As part of a project to establish a global picture of FGSC diversity, we determined the prevalence of FGSC species and toxins associated with diseased wheat, barley, and corn (maize) crops in South Africa. Fusarium graminearum, which is the most common FGSC species in the United States, accounted for more than 85% of the isolates collected from diseased wheat and barley. However, this species was completely absent from infected ears of corn, from which almost all isolates were identified as F. boothii. The predominance of F. graminearum among wheat and barley isolates, and the near exclusivity of F. boothiii among corn isolates, was observed across all cultivars, collection dates, and provinces sampled. These results indicate that F. graminearum may be less able to cause disease on corn than are other members of the FGSC. Currently, F. graminearum is the only member of the FGSC that is commonly found in U.S. cereals. As such, the results reported here are critical to promoting food safety and cereal production through improved detection of novel FGSC pathogens and through plant quarantine and variety improvement efforts that account for the entire spectrum of FGSC pathogens and toxin types.
Technical Abstract: Species identity and trichothecene toxin potential of 560 members of the Fusarium graminearum species complex (FGSC) collected from diseased wheat, barley and maize in South Africa was determined using a microsphere-based multilocus genotyping assay. Although three trichothecene types (3-ADON, 15-ADON and NIV) were represented among these isolates, strains with the 15-ADON type predominated on all three hosts. A significant difference, however, was identified in the composition of FGSC pathogens associated with Gibberella ear rot (GER) of maize as compared to Fusarium head blight (FHB) of wheat or barley (P < 0.001). Fusarium graminearum accounted for more than 85% of the FGSC isolates associated with FHB of wheat and barley (N = 425), and was also the dominant species among isolates from maize roots (N = 35). However, with the exception of a single isolate identified as an interspecific hybrid between F. boothii and F. graminearum, GER of maize (N = 100) was exclusively associated with F. boothii. The predominance of F. graminearum among FHB isolates, and the near exclusivity of F. boothiii among GER isolates, was observed across all cultivars, collection dates, and provinces sampled. Because these results suggest a difference in host preference among species of the FGSC, we hypothesize that F. graminearum may be less well adapted to infect maize ears than other members of the FGSC.