BREEDING FOR HOST RESISTANCE TO FIRE BLIGHT
M. Kellerhals, S. Schütz, A. Patocchi
Breeding for fire blight resistance in apple and pear has a long tradition. It was primarily related to the importance of the disease in the area where breeding programs are located. The main sources of resistance are wild species with low quality fruits. To introgress these sources of resistance, several breeding generations are required to develop resistant varieties with commercial fruit quality. Different methods are currently applied to speed up the generation cycle. However, also commercial cultivars and modern breeding material show considerable differences in susceptibility. Genotypes carrying a high level of resistance can be used as parents in breeding. Phenotypic scoring of resistance is mainly done by shoot inoculation tests on grafted plants in greenhouses. These tests can be complemented by outdoor flower inoculation tests to achieve a more comprehensive resistance evaluation. Progress in the development of molecular markers closely linked to fire blight resistance loci allow breeders for more efficient selection.