Abstract: A rising number of pathogens along with a diminishing choice of plant protectants and an increasing public concern about pesticide use demand a multi-pronged strategy in order to guarantee healthy plants in many apple-growing areas. Plant breeding can significantly contribute to reach this objective. The apple breeding program of Agroscope in Waedenswil, Switzerland, has considered breeding for disease resistance as an important objective since 1984. In order to develop sustainable new multi-resistant varieties several cruxes have to be solved. The search for potential diseases resistance sources is one of those, especially challenging with new appearing diseases. However, wild and exotic sources are often a useful source for monogenic resistance loci. Additionally, heirloom cultivars and accessions together with selected modern genotypes are promising to be the basis for polygenic resistance. A broad range of traditional Swiss apple genetic resources was evaluated for their resistance and tolerance towards apple scab, powdery mildew and fire blight. Moreover, their eating quality and storage performance were analysed. This is a valuable basis for the choice of interesting accessions for new crosses in breeding. The approach was conducted in collaboration with the NGO FRUCTUS, the Research Institute of Organic Agriculture as well as the private breeding program Poma Culta. First progenies of such crosses are fruiting and will be tested for market performance. The approach to achieve more durable resistance, using monogenic disease resistance is followed by pyramiding several resistance genes in one genotype. Marker-assisted breeding is a valuable tool to achieve this goal. With the switch from SSR markers towards single nucleotide polymorphism (SNP) markers the selection of genotypes with pyramided resistance genes (R-genes) against e.g. apple scab is facilitated and more economic. Pyramiding several R-genes against apple scab and combining them with R-genes against several other disease as well as with markers for genetic loci related to high fruit quality and good production is a major goal of the Agroscope apple breeding program. The implementation of modern technologies in breeding additionally to the use of genetic material of traditional accessions could help to solve important plant pathology problems.
