Molecular Cytogenetic Organization of 5S and 18S rDNA Loci in Aster ageratoides var. ageratoides, A. iinumae (=Kalimeris pinnatifida) and A. microcephalus var. ovatus in Japan

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Detailed karyotypes of diploid Aster ageratoides var. ageratoides (2n=18), diploid A. iinumae (=Kalimeris pinnatifida) (2n=18) and tetraploid A. microcephalus var. ovatus (2n=36) 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.
財団法人日本メンデル協会の論文