title: The chromosomes of Citrus and Poncirus species and hybrids: identification of characteristic chromosomes and physical mapping of rDNA loci using in situ hybridization and fluorochrome banding.
abstract: In situ hybridization of 18S-5.8S-25S rDNA probes labeled with biotin or rhodamine and 5S rDNA probes labeled with digoxigenin was used to locate rDNA sites on root-tip metaphase chromosomes of Citrus sinensis L. (2n = 2x = 18), Poncirus trifoliata L. Raf. (2n = 2x = 18), and Citrus x Poncirus hybrids (2n = 2x = 18). Counterstaining with the fluorochromes chromomycin A3 and DAPI uniquely identified many but not all chromosomes. C. sinensis had five 18S-25S rDNA sites, P. trifoliata had seven, and three different Citrus x Poncirus hybrids had five or six sites. Four 5S rDNA sites were detected, mostly linked to 18S-25S rDNA sites. Overall we observed high levels of chromosomal heterozygosity in all accessions examined.
authors.affiliation: Department of Cell Biology, John Innes Centre, Norwich, England.
authors.forename: M L
authors.initials: ML
authors.lastname: Roose
authors.forename: T
authors.initials: T
authors.lastname: Schwarzacher
authors.forename: J S
authors.initials: JS
authors.lastname: Heslop-Harrison
mesh_terms: D002871:Chromosome Banding / Q000379:methods*; D002874:Chromosome Mapping; D002875:Chromosomes; D002957:Citrus / Q000235:genetics*; D004275:DNA, Ribosomal; D005456:Fluorescent Dyes; D017403:In Situ Hybridization / Q000379:methods*; D007211:Indoles; D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D012341:RNA, Ribosomal, 5S
chemical_list: D004275:DNA, Ribosomal; D005456:Fluorescent Dyes; D007211:Indoles; D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D012341:RNA, Ribosomal, 5S; C065039:RNA, ribosomal, 25S; C007293:DAPI