Over the last 10 years the sensitivity of Septoria tritici, an important fungal pathogen of cereals, towards triazole fungicides decreases (shifting). Different mutations have been found within the target enzyme of the fungicides, a sterol-alpha-demethylase (CYP51) which are belived to be the reason for different resistance classes. Because today, there are no data aivalable about the appearance of the mutations and their proportion, a reltime-PCR assay was established to distinguish and quantify the most important mutations to close this gap (fig. 1).

 

Fig. 1 Development of a realtime-PCR assay for relative quantification of resistance classes

 

 

On the basis of S. tritici-isolats, primer systems were developed to detect the main resistance classes (R4, R6, R7) and the unmutated wildtype (S). The detection and relative quantification of the races was validated by field samples (hplotype mixtures) with known ration of resistance classes, determined by sequencing. A first screening of wheat samples from more than 50 sites all over germany showed changes in the composition of S. tritici populations (fig 2.).

 

         R7                                                                                                   R6    

Distribution

 

Fig. 2 Distribution of different resistance classes in the beginning (EC37) and the end of the vegetation period.