Trichothecene chemotypes of Fusarium culmorum infecting wheat in Tunisia

Fusarium culmorum is a major pathogen associated with Fusarium head blight (FHB) of wheat in Tunisia. It may cause yield loss or produce mycotoxins in the grain. The objectives of the present study were threefold: to evaluate by PCR assays the type of mycotoxins produced by 100 F. culmorum isolates recovered from different regions in Northern Tunisia, to determine the amount of mycotoxin production by HPLC analysis, and to analyse for correlations between the amount of mycotoxin produced and the aggressiveness of isolates. PCR assays of Tri5. Tri7,Tri13, and Tri3 were used to predict whether these isolates could produce nivalenol, 3-acetyl-deoxynivalenol, or 15-acetyl-deoxynivalenol. Two of the isolates were predicted to produce NIV, whereas the others were predicted to produce 3-AcDON. Trichothecene production was confirmed and quantified by high pressure liquid chromatography (HPLC) in 28 isolates, after growth on wheat grains, and in a liquid Mycotoxin Synthetic medium (MS). All strains produced DON/3-AcDON at detectable levels ranging from 21 mu g/g to 11.000 mu g/g of dry biomass on MS medium and from 10 mu g/g to 610 mu g/g on wheat grain. The evaluation of the relationship between 3-AcDON production and aggressiveness of 17 strains revealed a significant difference in aggressiveness among the isolates. Moreover, only a significant correlation was revealed between aggressiveness and the amount of 3-AcDON produced on MS medium (r= 0.36). Chemotyping of F. culmorum isolates is reported for the first time for isolates from Tunisia, and highlights the important potential of F. culmorum to contaminate wheat with 3-AcDON trichothecenes. (C) 2010 Elsevier B.V. All rights reserved.