Breeding of plum cultivars resistant to plum pox virus

Plum pox virus is a serious problem in plum production in Germany. Because of the poor fruit quality of the present resistant cultivars we started a plum breeding programme at Hohenheim in 1980. We used 'Stanley','Ruth Gerstetter' and 'President' as donors of resistance, of which 'Stanley' proved to be the best. In the progenies of this cultivar we found the quantitative type of resistance. Resistance tests were made in an orchard with naturally infected young trees of 'Hauszwetsche'. More than 40% of the tested seedlings were tolerant or resistant. From 1,000 seedlings of the first breeding cycle, six hybrids were selected as new tolerant or resistant cultivars and introduced recently. These new cultivars are described.