Magdy Hussein Abd El-Twab

Molecular cytogenetic identification of the parental genomes in the intergeneric hybrid between Leucanthemella linearis and Nipponanthemum nipponicum during meiosis and mitosis

Abstract The genomes of Leucanthemella linearis (2n=18) and Nipponanthemum nipponicum (2n=18) were studied in the chromosome complement of their F1 hybrid (2n=18) during meiosis and mitosis by DNA in situ hybridization and fluorochrome banding. Genomic in situ hybridization (GISH) using the total genomic DNA of N. nipponicum as a probe showed that the parental genomes in the chromosome complement of the hybrid were generally in separate domains during meiosis. Chromosome translocations were encountered and 18 univalents were usually observed at diakinesis and metaphase I. Meiotic abnormalities of chromosomes such as bridges, laggards and fragments were manifested mainly in the genome of L. linearis and after fluorescence in situ hybridization (FISH)using the 45S rDNA pTa71 probe showed that the parental genomes were differentiable in the hybrid. One 45S rDNA signal appeared on one of the nine chromosomes originating from N. nipponicum and thr e signals appeared in three of the nine chromosomes originating from L. linearis. Analysis of mitotic metaphase chromosomes after GISH using the total genomic DNA of N. nipponicum as a probe, positive GISH bands at the terminal region of chromosomes were correlated with positive DAPI (AT-rich) banded regions.

Structural Differences of Chromosomes in Plants Detected by Fluorescence in situ Hybridization Using Probes of rDNA, Arabidopsis-type Telomere Sequence Repeats and pCrT7-4

The chromosomal sites of 5S rDNA, 45S rDNA and Arabidopsis-iypt telomere sequence repeats characterize individual species and population constitutions in chrysanthemums and cycads and those of Sau3A in spruces. The sites of the telomere sequence repeats in the cycad chromosomes occur not only in the usual terminal regions of chromosome-arms as small dots, but also in several centromeric to proximal regions as relatively large signals. Large signals of the 278 bp DNA segment with respect to Cycas revoluta involved with pCrT7-4. The Y-chromosome of Cycas revoluta was distinct by lack of the large signal of pCrT7-4 and the Arabidopsis-type telomere sequence repeats. A highly conserved chromosomal location of these genes lead to speculation on the karyotype evolution and species property of the chrysanthemum and cycad groups.