INTERSPECIFIC HYBRIDIZATION IN GENUS FRAGARIA AND EVALUATION OF THE HYBRIDS FOR COLD HARDINESS AND RED STELE RESISTANCE USING IN VITRO METHODS

For the hybridization 10 Fragaria species and forms with different genomic constitution and ploidy level were used. The highest berry set (55.8%) was in combinations where parental forms were octoploids: F. virginiana, F. chiloensis and F. ananassa. The highest output of fertile hybrids was in combinations where estimated ploidy level of seedlings was 2, 6 and 8x. The hybridization results were highly influenced by genomic constitution of parental forms. Depending on genomic constitution of parental forms berry set in diploid level varied between 0 and 42.7%, hybrid fertility between 56.5 and 89%. Utilizing the method of isolated embryos, it was possible to increase the output of seedlings up to 16-58%. For some combinations, it was the only method to receive seedlings. For screening of the hybrids for cold hardiness, we used freezing in vitro at -11°C. The viability of strawberry plants after freezing in vitro varied from 20.7% (‘Elsanta’) to 100% (seedlings F. orientalis x F. vesca and F. ananassa x F. virginiana). RAPD markers were used to identify Phytophthora fragariae resistance gene rpf1 in the interspecific hybrids.