, H. 2007. Chromosomal study of lettuce and its allied species (Lactuca spp., Asteraceae) by means of karyotype analysis and fluorescence in situ hybridization. * Hereditas 144: 235Á243. Lund, Sweden. eISSN 1601-5223. Received May 14, 2007. Accepted October 5, 2007 In this study, in addition to the karyotype analysis, the chromosomal distributions of 5S and 18S rDNAs, and the Arabidopsis-type (T 3 AG 3 ) telomeric sequences were detected by means of fluorescence in situ hybridization (FISH) to promote the information of chromosomal organization and evolution in the cultivated lettuce and its wild relatives, L. sativa, L. serriola, L. saligna and L. virosa. The karyotype analysis revealed the dissimilarity between L. virosa and the remaining species. In all four Lactuca species studied, one 5S rDNA and two 18S rDNA loci were detected. The simultaneous FISH of 5S and 18S rDNAs revealed that both rDNA loci of L. sativa, L. serriola and L. saligna were identical, however, that of L. virosa was different from the other species. These analyses indicate the closer relationships between L. sativa/L. serriola and L. saligna rather than L. virosa. Arabidopsis-type telomeric sequences were detected at both ends of their chromatids of all chromosomes not in the other regions. This observation suggests the lack of telomere-mediated chromosomal rearrangements among the Lactuca chromosomes.

The fluorescence in situ hybridization (FISH) using 5S and 18S rDNA probes was applied to four species of the genus Artemisia. In all four Artemisia species, 5S and 18S rDNA were located in the terminal position. Moreover, all 18S rDNA sites were the same number and collocated with 5S rDNA. The collocation of the 5S and 18S rDNA might be a common feature of chromosome evolution in the genus Artemisia. In section Dracunculus have eight and nine rDNA sites while section Artemisia has four rDNA sites. Despite the polyploidy had been observed, the number of rDNA sites were relatively constant within the section Dracunculus and Artemisia respectively.

SummaryTo resolve the discrepancy among previous karyotype descriptions, chromosome comparative study between two closely related cucumber cultivars, C. sativus L. cv. Borszczagowski and cv. Monastyrski, was performed by chromosome preparation technique with enzymatic maceration, and fluorescent banding method with chromomycin A 3 (CMA) and 4Ј,6-diamidino-2-phenylindole (DAPI). Heterochromatic band polymorphisms were detected in chromosomes 2, 3, 5 and 7, whereas no chromosomal polymorphism was found in chromosomes 1, 4 and 6. In cv. Borszczagowski chromosome 2, CMA

Summary Detailed karyotypes and the fluorescence in situ hybridization (FISH) using 5S and 18S rDNA probes was applied to 3 species of the genus Juniperus. The number of chromosomes of J. chinensis var. sargentii and J. lutchuensis was 2nϭ22, except for J. chinensis var. procumbens (2nϭ44). Chromosomal sites of 5S rDNA were on one pair of the short arm of the median-centromeric chromosome and 18S rDNA were at the secondary constriction. No minor signals of 5S and 18S rDNA probes were detected in the Juniperus chromosomes. We developed karyotypes using McFISH with 5S and 18S rDNA, and reported the first time chromosome makers of the family Cupressaceae.

Detailed karyotypes of diploid Aster ageratoides var. ageratoides (2nϭ18), diploid A. iinumae (ϭKalimeris pinnatifida) (2nϭ18) and tetraploid A. microcephalus var. ovatus (2nϭ36) were constructed on the basis of chromosome lengths, arm ratios and multi color fluorescence in situ hybridization (McFISH) with 5S and 18S ribosomal RNA gene sequences as probes. The karyotype of A. iinumae was morphologically similar to those of A. ageratoides var. ageratoides, however, the size of the chromosomes of A. iinumae was apparently smaller (S-type chromosomes) compared to those of A. ageratoides (L-type chromosomes). The chromosomes of A. microcephalus var. ovatus, a putative amphidiploid between them consisted of the 18 large chromosomes (L-type chromosomes) and the 18 smaller chromosomes (S-type chromosomes). The McFISH with 5S rDNA and 18S rDNA of each A. ageratoides and A. iinumae chromosomes tagged 4 out of 18 chromosomes. Whereas A. microcephalus var. ovatus have 5S rDNA and 18S rDNA sites equal to the sum of the numbers in the two diploids (A. ageratoides and A. iinumae), 4 on the L-type chromosomes and 4 on the S-type chromosomes. The locations of the rDNA sites in A. microcephslus var. ovatus are corresponding to those of A. ageratoides and A. iinumae.