The dominant component of the genome of angiosperms are repetitive sequences, including retroelements. Various content of these sequences results in variation in size of the genome within both species and genus. Any type of repetitive sequences may be species-specific or-genomowo commonly occur either within the genus or families exhibiting the characteristic chromosomal location. The characteristics of species include speckled pattern and chromosomal location of 18S-5, 8S-25S rDNA and 5S rDNA. U allopoliploidów, compared with ancestralnymi genomes, changes can occur translocation involving chromosome fragments and translocation of repetitive sequences specific for one of the other genomes, and reducing the number of rDNA loci and their expression. In determining the relationship between the species are important GISH results.