Search

The karyotype, C-banding, and chromosomal location of 45S and 5S rDNA of Nicotiana alata were studied by methods of wall digestion and hypotonic treatment, BSG, and double color fluorescent in situ hybridization, respectively. Karyotype analysis of root tip cells of four N. alata accessions showed that the average karyotype formula was 2n = 2x = 12m + 6st, the variation and average value of arm ratio was 1.14~4.22 and 2.17, respectively. The rate of the longest and minimum chromosome was 2.16, and the karyotype classification was 2B of Stebbins system (1971). Results of C-banding study showed that chromosome C-banding of N. alata was abundant with 25 bands being displayed, including 7 centromeric bands, 15 terminal bands, and 3 intercalary bands. Results of FISH study showed, in metaphase chromosomes of root tip cell of N. alata, there were three pairs of 45S rDNA loci, locating on IS, IIIS, and VL, respectively (L and S represented chromosome long and short arm respectively, and the Roman number indicated chromosomes serial number; the same hereinafter), and two pairs of 5S rDNA loci, locating on IL and IVS, respectively. Pair I of homologous chromosome had loci of both 45S and 5S rDNA. These results could provide reference for studies on phylogenesis of genus Nicotiana, and were of great significance to genetic breeding and germplasm innovation in tobacco.