Cytogenetic Comparison among Three Cultivars of Cucumber (cucumis Sativus L.) by Using Post-Heated DAPI Band, 45S and 5S Rdna Sites

The positions of heterochromatic bands, 45S and 5S rDNA regions were detected on the chromosomes in three cultivars of cucumber (Cucumis sativus L.). The post-heated DAPI bands, which revealed heterochromatic region, were observed on the both terminal and pericentromeric regions of most of the chromosomes in three cultivars. However, these band patterns were different between European and Eastern Asian cultivars. The major 45S rDNA sites were found around the centoromeric region of the chromosomes 1, 2 and 5, and the minor 45S rDNA sites were found around centoromeric region of the chromosomes 3 and 7. The positional variation of this region was not found among three cultivars, but size difference was observed in the chromosome 5. The 5S rDNA site was observed on the interstitial region of the chromosome 6 in all of the cultivars studied. These results indicated that the variation of chromosome structure among cucumber cultivars occurred in the heterochromoatic region and suggested that the genetic variation in cucumber cultivars would be revealed by strict analysis and comparison for the position and size of heterochromatic region.