ABSTRACT
Disease-and pest-resistant cultivars can significantly contribute to sustainable and resilient cultivation of apples. Developing pest-resistant and especially disease-resistant varieties has been a major objective in most apple breeding programmes worldwide for several decades. However, specific breeding aims differ for different production areas and their climatic conditions. For example in Washington State (the United States), owing to little rainfall and very dry climatic conditions, apple scab (Venturia inaequalis) is rarely present and therefore scab-resistant cultivars would not bring an added value. However, breeding for resistance to scab is a major target for breeders elsewhere. A survey in 1996 of 42 apple breeders from 29 countries representing four continents reported a common principle objective of combining high fruit quality with disease and pest resistance in new cultivars (Laurens, 1999). Typically, pest resistances are less frequently considered as breeding objectives. In apple breeding, it is necessary to focus on a limited number of objectives as the breeding cycle is long due to the juvenile phase and a high level of heterozygosity.
