EN
First programs of apple and pear breeding for resistance to fire blight were worked out in the United States of America in second half of XIX century. At present such programs are also conducted in other countries, particularly in Europe. It was found that the resistance to diseases is polygenically inherited. In apple it is governed by dominant additive genes carried in the heterozygous conditions, but in pear – presumably by recessive genes. Till now it was not possible to develop the immune cultigens, however there are forms with high degree of resistance, e.g. apples marked with code Re, clones G of rootstocks, or pears 'Harrow Queen', 'Harrow Delight' and 'Harrow Sweet'. Also 2 of 10 new Polish apple cultivars and clones: 'Free Redstar' and J-79 appeared to be highly resistant. It was found that the sources of resistance occur in some old local, of ten wild growing, genotypes originating from Asia, Near East and some European countries. The advanced molecular technologies utilizing genes for lytic proteins, proteins inducing resistance as well as those directed for silencing or over-expression of native genes, allowed to obtain clones with increased resistance to fire blight. Intensive research works on development of molecular markers for resistance are also performed.