具翼烟草(Nicotiana alata)核型、C带与rDNA染色体定位研究

采用去壁低渗法、BSG法和双色荧光原位杂交技术，分别开展了具翼烟草（Nicotiana alata）的核型分析、C显带与45S和5S rDNA染色体定位研究。4个具翼烟草收集系根尖细胞有丝分裂中期染色体平均核型为2n=2x=12m+6st，染色体臂比的变异幅度为1.14~4.22，平均臂比值为2.17，最长与最短染色体之比为2.16，属2B型。C带研究结果显示，具翼烟草中期染色体C带丰富，多态性良好，共显带25条，包括7条着丝粒带、15条端带和3条中间带。45S和5S rDNA染色体定位研究结果显示，具翼烟草根尖细胞有丝分裂中期染色体细胞相分别显示了3对45S rDNA和2对5S rDNA基因位点信号，45S rDNA基因位点分别位于I S、III S、V L上，2对5S rDNA基因位点分别位于I L、IV S上（字母L和S分别代表染色体长臂和短臂，罗马数字代表同源染色体序号）。在I号同源染色体上同时存在45S和5S rDNA基因位点。研究结果对烟草属系统起源、遗传进化以及遗传育种等领域的进一步研究具有重要的参考价值。 

Study on karyotype,C-banding and rDNA chromosome locus in Nicotiana alata

The karyotype, C-banding, and chromosome locus 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.