Regional differences in species composition and toxigenic potential among Fusarium head blight isolates from Uruguay indicate a risk of nivalenol contamination in new wheat production areas.

Members of the Fusarium graminearum species complex (FGSC) are the primary cause of Fusarium head blight (FHB) of wheat, and frequently contaminate grain with trichothecene mycotoxins that pose a serious threat to food safety and animal health. The species identity and trichothecene toxin potential of 151 FGSC isolates collected from wheat in Uruguay were determined via multilocus genotyping. Although F. graminearum with the 15ADON trichothecene type accounted for 86% of the isolates examined, five different FGSC species and all three trichothecene types were identified in this collection. This is the first report of Fusarium asiaticum, Fusarium brasilicum, Fusarium cortaderiae, and Fusarium austroamericanum from Uruguay. In addition, we observed significant (P<0.001) regional differences in the composition of FGSC species and trichothecene types within Uruguay. Isolates of F. graminearum with the 15ADON type were the most prevalent in western provinces (95%), while F. asiaticum (43%) and the NIV type (61%) predominated in the new wheat production zone in Cerro Largo along Uruguay's eastern border with Brazil. F. graminearum isolates (15ADON type) were significantly (P<0.005) more aggressive on wheat than were isolates from the other species examined (NIV or 3ADON types). However, F. graminearum isolates (15ADON type) were significantly (P<0.05) more sensitive to tebuconazole than isolates from other species (NIV type). These results document substantial heterogeneity among the pathogens responsible for FHB in Uruguay. In addition, the regional predominance of the NIV trichothecene type is of significant concern to food safety and indicates that additional monitoring of nivalenol levels in grain may be required.

High-throughput method for ranking the affinity of peptide ligands selected from phage display libraries.

The use of phage display peptide libraries allows rapid isolation of peptide ligands for any target selector molecule. However, due to differences in peptide expression and the heterogeneity of the phage preparations, there is no easy way to compare the binding properties of the selected clones, which operates as a major "bottleneck" of the technology. Here, we present the development of a new type of library that allows rapid comparison of the relative affinity of the selected peptides in a high-throughput screening format. As a model system, a phage display peptide library constructed on a phagemid vector that contains the bacterial alkaline phosphatase gene (BAP) was selected with an antiherbicide antibody. Due to the intrinsic switching capacity of the library, the selected peptides were transferred "en masse" from the phage coat protein to BAP. This was coupled to an optimized affinity ELISA where normalized amounts of the peptide-BAP fusion allow direct comparison of the binding properties of hundreds of peptide ligands. The system was validated by plasmon surface resonance experiments using synthetic peptides, showing that the method discriminates among the affinities of the peptides within 3 orders of magnitude. In addition, the peptide-BAP protein can find direct application as a tracer reagent.