Study On Some Species Of Citrus And Ponirus By 45S RDNA-FISH

Citrus L.( Rutaceae , Aurantinoideae) is one of the most economic fruit trees in the world, which is mainly distributed to Asia and subtropic regions. China is one of the centers of Citrus origin and genetic variation, and is rich in many inheritance germ plasm resources including cultivars, wild and semi-wild species , and natural or man-made hybrid types, as well as lots of close relationship genera plants. Owing to its large frequency of bud variation and its apomixis predominance, as well as its extensive fecundation fertilizability and long-term natural hybridization, Citrus has the characteristics of being various in its tree exterior shape, and intricate in its kinship, so it is relatively difficult to probe into its origin and evolution .Fluorescence in situ hybridization(FISH) technology, based on the complementarity theory, can obtain the precise position of especially modified nucleotide numerator probe on the chromosome , and this technology, on the basis of the cytogenetics and molecular genetics, provides a new, quick and efficient means to study on the chromosomal structure, gene mapping, karyotyping of Citrus L. at molecule level. Studies on quadrant Citrus and close relationship genera Poncirus with FISH were conducted. In details, by adopting 45S rDNA for probe, 45S rDNA cross telltale number and relatively loci fairing were clearly abtained. The results were as follows:By adopting 45S rDNA as probe, the results indicated that there were two to five cross loci in some Citrus chromosomes. One to three was in the end of one chromosomal short arm, and its cross signal was relatively outstanding. And also, the cross signal had not been detected on its homologous chromosome. The other one or two cross loci was detected on the other two chromosomes's satellite chromosome and degree narrow cicatrices, respectively, and the cross signal on the satellite chromosome was very strong.By adopting 45S rDNA as probe, the studies indicated that there were two to four cross loci in some Poncrius chromosomes. One or two were on the near-point -of-centromere and its cross signal was weak. The rest one or two were on satellite chromosome and the cross signal was strong. For the loss of the satellite chromosome and degree narrow cicatrices, the rDNA loci were lost on the other corresponding homologous chromosome.The Fluorescence in situ Hybridization displayed the different cross loci and the unconspicuous,...