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Molecular cytogenetic techniques and computer-aided karyotyping were applied to characterize the chromosomes of spinach (Spinacia oleracea L., 2n = 12). Chromosome lengths, arm ratios, and degrees of condensation at prometaphase chromosomes were analyzed using a software Chromosome Image Analyzing System III (CHIAS III). DNA probes prepared from rice (Oryza sativa L.) rDNA were applied to the spinach chromosomes by the fluorescence in situ hybridization (FISH) method. Three 45S rDNA loci were detected at the nucleolar organizing region (NOR) of Chromosome 5, and at terminal positions of short arms of Chromosomes 2 and 6. The loci of 5S rDNA were also found at three locations. One was at the subtelomeric region of the long arm of Chromosome 2 and the other two were at the proximal region of the long arm of Chromosome 5. All spinach chromosomes were identified which will provide valuable information for mapping genes on these chromosomes.

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5S ribosomal DNA (rDNA) was visualized on the somatic metaphase chromosome of persimmon (Diospyros kaki) and ten wild Diospyros species by fluorescent in situ hybridization (FISH). The digoxigenin (DIG)-labeled 5S rDNA probe was hybridized onto the chromosomes and visualized by incubation with anti-DIG-fluorescein isothiocyanate (FITC). Strong signals of 5S rDNA probe were observed on several chromosomes of Diospyros species tested. Furthermore, multicolor FISH using 5S and 45S rDNA probes differently labeled with DIG and biotin, revealed separate localization of the two rDNA genes on different chromosomes of Diospyros species tested, suggesting that 5S and 45S rDNA sites can be used as chromosome markers in Diospyros. The number of 5S rDNA sites varied with the Diospyros species. More 5S rDNA sites were observed in four diploid species native to Southern Africa than in three Asian diploid species. The former had four or six 5S rDNA sites while the latter had two. Three Asian polyploidy species had four to eight 5S rDNA sites. Among the Asian species, the number of 5S rDNA sites seemed to increase according to ploidy level of species. These features of 5S rDNA sites were very similar to those of 45S rDNA sites in Diospyros. Phylogenetic relationship between D. kaki and wild species tested are discussed based on the number and chromosomal distribution of 5S and 45S rDNA.

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higher eukaryotes, rDNAs are organized into two distinct multigene families, one coding for 45S rRNA and the other coding for 5S rRNA ( Suzuki et al., 1996 ). In plants, 45S rDNAs are highly repeated and arranged in tandem at one or a few chromosomal loci

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the late 1980s and has become a powerful tool for localizing specific DNA sequences on plant chromosomes ( Schwarzacher et al., 1989 ). The rDNAs (45S and 5S), which are repeated sequences in the genome, are commonly used for physical mapping of plant

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often are combined with more variable, rapidly evolving intergeneric spacer regions ( Volkov et al., 2017 ). Frequently used loci include the 5S and 45S ( Ribeiro et al., 2008 ; Volkov et al., 2017 ). The 45S and 5S rDNA loci are usually located at

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, FISH is another technique providing chromosomal markers that show the positions of specific genes, thereby permitting chromosomal identification. The use of FISH with 5S and 45S rDNA probes has provided molecular cytogenetic markers for the

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ribosomal RNA gene families (18S-28S rDNA and 5S rDNA) using fluorescent in situ hybridization (FISH). Fig. 1. Mature Christia obcordata plants grown under greenhouse environment at the U.S. Department of Agriculture, Agriculture Research Service unit in

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manufacturer's protocol. Total nucleic acid in the extracts was determined by spectrophotometry; 100 ng of total nucleic acid per sample was used as a template for quantitative polymerase chain reaction (qPCR). CLas was amplified using 16S rDNA primers and

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rDNA. Because the ITS1 and ITS2 regions exhibit high divergence among species and populations, they are suitable targets for species identification; in contrast, 18S, 5.8S, and 26S exhibit lower divergence among species and have been explored to study

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from colonies maintained on infected M. paniculata or infected Citrus spp. Because C Las bacterial numbers in infected M. paniculata often are too low to be detected by 16S rDNA-based C Las-specific quantitative polymerase chain reaction ( Li et

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