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.