Lemons, limes and citron constitute a group of closely related Citrus species, whose species delimitations and taxonomic relationships are unclear. In order to identify karyotypic similarities and species relationships within this group, the CMA+/DAPI– banding pattern and the distribution of the 5S and 45S rDNA sites of 10 accessions of lime, lemon, and citron were investigated. The four cultivars of C. limon analyzed showed the same pattern of CMA+ bands and rDNA sites, suggesting that they originated from a single germplasm, later differentiated by distinct somatic mutations. The lemons C. jambhiri, C. limonia and C. volkameriana displayed karyotypes very similar to each other, but they differed from C. limon by the absence of a single chromosome with one band in each telomere. The limes, C. aurantifolia and C. limettioides, seemed less related to each other and exhibited different heteromorphic chromosome pairs. In C. aurantifolia, the presence of a chromosome type unknown in all other Citrus species cytologically known so far supports the assumption that this accession may be derived from a hybrid with a species from the subgenus Papeda or from another genus. Citrus medica was the only homozygous accession of this group and all of its chromosome types were clearly represented in limes and lemons, some of them forming heteromorphic pairs. The analysis of the distribution of rDNA sites allowed a further refinement of the comparison among accessions. The lemons and limes were heterozygous for all rDNA sites, whereas C. medica was entirely homozygous. These data support the hypothesis that C. medica is a true species while the other nine accessions are hybrids.   

1.
Asíns MJ, Mestre PF, Herrero R, Navarro L, Carbonell EA: Molecular markers: a continuously growing biotechnology area to help citrus improvement. Fruits 53:293–302 (1998).
2.
Barrett HC, Rhodes AM: A numerical taxonomic study of affinity relationships in cultivated Citrus and its close relatives. Syst Bot 1:105–136 (1976).
3.
Befu M, Kitajima A, Hasegawa K: Chromosome composition of some Citrus species and cultivars based on the chromomycin A (3) (CMA) banding patterns. J Japan Soc Hort Sci 70:83–88 (2001).
4.
Befu M, Kitajima A, Hasegawa K: Classification of the citrus chromosome with same types of chromomycin A banding patterns. J Japan Soc Hort Sci 71:394–400 (2002).
5.
Bretó MP, Ruiz C, Pina JA, Asíns MJ: The diversification of Citrus clementina Hort. ex Tan., a vegetatively propagated crop species. Mol Phylogenet Evol 21:285–293 (2001).
6.
Cornélio MTMN, Figueirôa ARS, Santos KGB, Carvalho R, Soares Filho WS, Guerra M: Chromosomal relationships among cultivars of Citrus reticulata Blanco, its hybrids and related species. Plant Syst Evol 240:149–161 (2003).
7.
Esen A, Scora RW: Amylase polymorphism in Citrus and some related genera. Am J Bot 64:305–309 (1975).
8.
Fang DQ, Roose ML: Identification of closely related Citrus cultivars with inter-simple sequence repeat markers. Theor Appl Genet 95:408–417 (1997).
9.
Fann JY, Kovarik A, Hemleben V, Tsirekidze NI, Beridze TG: Molecular and structural evolution of Citrus satellite DNA. Theor Appl Genet 103:1068–1073 (2001).
10.
Federici CT, Fang DQ, Scora RW, Roose ML: Phylogenetic relationships within the genus Citrus (Rutaceae) and related genera as revealed by RFLP and RAPD analysis. Theor Appl Genet 96:812–822 (1998).
11.
Gottlob-McHugh SG, Lévesque M, MacKenzie K, Olson M, Yarosh O, Johnson DA: Organization of the 5S rRNA genes in the soybean Glycine max (L.) Merrill and conservation of the 5S rDNA repeat structure in higher plants. Genome 33:486–494 (1990).
12.
Guerra M: Cytogenetics of Rutaceae. V. High chromosomal variability in Citrus species revealed by CMA/DAPI staining. Heredity 71:234–241 (1993).
13.
Guerra M, Pedrosa A, Silva AEB, Cornélio MTM, Santos KGB, Soares Filho WS: Chromosome number and secondary constriction variation in 51 accessions of a Citrus germplasm bank. Braz J Genet 20:489–496 (1997).
14.
Guerra M, Santos KGB, Silva AEB, Ehrendorfer F: Heterochromatin banding patterns in Rutaceae-Aurantioideae – A case of parallel chromosomal evolution. Am J Bot 87:735–747 (2000).
15.
Herrero R, Asíns MJ, Carbonell EA, Navarro L: Genetic diversity in the orange subfamily Aurantioideae. I. Intraspecies and intragenus genetic variability. Theor Appl Genet 92:599–609 (1996).
16.
Hirai M, Kozaki I, Kajiura I: Isozyme analysis and phylogenetic relationships of Citrus. Jpn J Breed 36:377–389 (1986).
17.
Longley AE: Polycarpy, polyspory and polyploidy in Citrus relatives. J Washington Acad Sci 15:347–351 (1925).
18.
Malik MN, Scora RW, Soost RK: Studies on the origin of the lemon. Hilgardia 42:361–382 (1974).
19.
Matsuyama T, Akihama T, Ito Y, Omura M, Fukui K: Characterization of heterochromatic regions in “Trovita” orange (Citrus sinensis Osbeck) chromosomes by the fluorescent staining and FISH methods. Genome 39:941–945 (1996).
20.
Miranda M, Ikeda F, Endo T, Moriguchi T, Omura M: Comparative analysis on the distribution of heterochromatin in Citrus, Poncirus and Fortunella chromosomes. Chromosome Res 5:86–92 (1997).
21.
Moore GA: Oranges and lemons: clues to the taxonomy of Citrus from molecular markers. Trends Genet 17:536–540 (2001).
22.
Moore GA, Castle WS: Morphology and isozymic analysis of open-pollinated Citrus rootstock populations. J Hered 79:59–63 (1988).
23.
Moscone EA, Matzke MA, Matzke AJM: The use of combined FISH/GISH in conjunction with DAPI counterstaining to identify chromosomes containing transgene inserts in amphidiploid tobacco. Chromosoma 105:231–236 (1996).
24.
Nicolosi E, Deng ZN, Gentile A, La Malfa S, Continella G, Tribulato E: Citrus phylogeny and genetic origin of important species as investigated by molecular markers. Theor Appl Genet 100:1155–1166 (2000).
25.
Pedrosa A, Schweizer D, Guerra M: Cytological heterozygosity and the hybrid origin of sweet orange [Citrus sinensis (L.) Osbeck]. Theor Appl Genet 100:361–367 (2000).
26.
Raghuvanshi SS: Cytological studies in Citrus IV. Evolution in genus Citrus. Cytologia 27:172–188 (1962).
27.
Roose ML, Schwarzacher T, Heslop-Harrison JS: 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. J Hered 89:83–86 (1998).
28.
Scora RW: IX. On the history and origin of Citrus. Bull Torrey Bot Club 102:369–375 (1975).
29.
Swingle WT, Reece PC: The botany of Citrus and its wild relatives, in Reuther W, Weber HJ, Batchelor LD (eds): The Citrus Industry. History, World Distribution, Botany and Varieties, vol I, pp 190–430 (University of California Press, Berkeley 1967).
30.
Tanaka T: Fundamental discussion of Citrus classification. Stud Citrol 14:1–6 (1977).
31.
Torres AM, Soost RK, Diedenhofen U: Leaf isozymes as genetic markers in Citrus. Am J Bot 65:869–881 (1978).
32.
Unfried I, Gruendler P: Nucleotide sequence of the 5.8S and 25S rRNA genes and of the internal transcribed spacers from Arabidopsis thaliana. Nucleic Acids Res 18:4011 (1990).
33.
Unfried I, Stocker U, Gruendler P: Nucleotide sequence of the 18S rRNA gene from Arabidopsis thaliana Co10. Nucleic Acids Res 17:7513 (1989).
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