Breeding of plums and prunes resistant to plum pox virus.

At Hohenheim we started a plum breeding programme to get new sharka-resistant cultivars with better fruit quality. In the last years we have recognized that the resistance of all cultivated plums is based on quantitative criteria and therefore relative. For this reason we changed our strategy for the resistance breeding. For the first breeding cycle we used special donors with quantitative resistance. Today, the qualitative resistance is more integrated. We intend to combine both types of resistance in the hexaploid genome of Prunus domestica to obtain an absolute and durable resistance. To achieve this aim, we have to consider the evaluation of resistance, the genetic resources, the inheritance of the resistance and also the breeding methods. The results of our resistance breeding study are presented.