Cytogenetic comparison among three cultivars of cucumber (Cucumis sativus L.) by using post-heated DAPI band, 45S and 5S rDNA sites

Abstract

ABSTRACT. 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.

Karyotype Analysis and Chromosomal Distribution of Repetitive DNA Sequences of <b><i>Cucumis metuliferus</i></b> Using Fluorescence in situ Hybridization

“…Images were taken under an Olympus AX70 Provis microscope equipped with an Olympus DP50 digital camera. After CMA staining, the slides were destained and FISH was carried out according to Tagashira et al [2009]. After single FISH, some of the probes were mixed and applied for multi-FISH.…”

“…Root-tips from 1-2 cm germinated seeds were collected, pretreated with 0.05% colchicine solution for 2 h at 4 ° C, fixed in 3: 1 ethanol:acetic acid for 1 h on ice, and washed in distilled water for 1 h. Root tip microscope slides were prepared according to previously described protocols [Tagashira et al, 2009;Hoshi et al, 2013].…”

Chromosomal localization of rDNA and DAPI bands in solanaceous medicinal plant Hyoscyamus niger L.

“…Although it does not necessarily reflect corresponding AT-rich regions, but the DAPI positive bands have proved to be similar to C-banding or Q-banding in most cases (Heng and Tsui 1993;Ali et al 2000). As such, the combination of DAPI banding pattern, localization of rDNA loci and conventional chromosome markers could be an effective tool to refine karyotypes facilitating chromosomal structural changes and identification of individual linkage groups (Ali et al 2000;Abd El-Twab and Kondo 2009;Tagashira et al 2009). …”

“…Further the same metaphase preparation could be used for delineation of DAPI bands. After FISH, DAPI preferentially stains heterochromatic regions (Tagashira et al 2009). Although it does not necessarily reflect corresponding AT-rich regions, but the DAPI positive bands have proved to be similar to C-banding or Q-banding in most cases (Heng and Tsui 1993;Ali et al 2000).…”

“…They may be unlinked on the same chromosome arm, or located on different chromosomes, but variation in locus size/copy number is known to occur across genotypes and geographical regions (Tagashira et al 2009). Although the occurrence of 5S rDNA sites has been shown to be associated with nucleolus in soybean, common bean (Shi et al 1996) and wheat (Mukai et al 1991), the occurrence of two rDNA gene families on the same chromosome as observed in Chlorophytum (Lavania et al 2005) as well as here is unusual and may serve as a marker to aid chromosome identification.…”