Virulence monitoring and the structure of powdery mildew populations between 2003 and 2010

Breeding for powdery mildew resistant wheat varieties needs information on the presence of virulences and the virulence structure of the current powdery mildew populations. In this work, we present a novel approach for virulence analyses by global analysis and not by analyzing the constituants of the population, as this was done in previous studies. Here, by planting the tester lines directly in the field, it is possible to screen the upcome of virulences during the whole season. Monitoring plots have been installed between 2003 and 2010 at 8 up to 17 sites all over Switzerland. More than 104 powdery mildew populations could be screened. The results show only little changes among the dominating resistances, but multiple virulences are likely to have increased. The virulence structures of the populations show very changing patterns over the years and over the sites. This may be linked to the wheat varieties cultivated and, probably more important, due to environmental factors. Unfortunately, these factors could not be studied within the present work. Overall, the here presented method of global virulence analysis meets the needs for breeding of resistant varieties. Future virulence screenings will analyse the efficacy and the durability of new resistances.