Efficacy of Blackleg Major Resistance Genes in in Germany.

is one of the major pathogens of oilseed rape (). It causes blackleg disease, which accounts for significant yield losses worldwide. Using cultivars that harbor major resistance () genes is one of the most effective control methods. However, the efficacy of major genes is related to the frequency of the corresponding avirulence () genes in a population. In this paper, we report the profiles of populations and the ratio of its mating types in Northern and Central regions of Germany. Eleven genes in five-hundred and seventy-four isolates were characterized either by applying cotyledon tests on a differential set or by amplifying avirulence gene-specific PCR markers. Fifty-two races were determined, among which the most dominant race was . Results showed that the resistance gene is 100% ineffective, some other major genes such as , and are partially effective (with corresponding frequencies ≤ 42%), while , , , and can still provide relatively effective resistance in the German fields investigated (with corresponding frequencies of 63-100%). Sexual reproduction is a factor that enhances the potential of to evolve under selection pressure. Mating types of the populations did not deviate from the ratio of 1:1 in the examined regions, indicating that sexual reproduction and ascospores play central roles in the lifecycle. Overall, this study provides an important dataset for the establishment of a strategic plan to preserve the efficacies of major genes in Germany by applying cultivar rotations of oilseed rape.