45S rDNA在不同倍性沙田柚染色体上的荧光原位杂交分析

 应用荧光原位杂交技术进行45S rDNA在不同倍性沙田柚中期染色体上的定位研究。结果表明: 不同材料的NOR位点表现出明显的多态性和杂合性, 即二倍体具4个45S rDNA位点, 四倍体单株t₁和t₂ 则分别具有10个和8个位点。位点在染色体上的位置包括短臂末端、着丝粒区域、着丝粒至短臂区域、着丝粒至长臂区域、长臂末端共5种不同类型。不同材料中包含的位置类型不完全相同。不同位置类型的位点数也不相同, 以着丝粒及着丝粒至短臂区域的类型位点数最多, 其次是短臂末端。同源四倍体和相应的二倍体相比, 出现了DNA水平的变异。对用于荧光原位杂交的柑橘染色体制片方法和rDNA在染色体上的分布位置、同源四倍体和相应二倍体的遗传差异分析、重复序列的染色体原位杂交用于染色体识别和物种演化研究等进行了讨论。

Chromosome Localization of 45S rDNA in Different Ploidy Citrus grandis by Fluorescence in situ Hybridization

Chromosome localization of 45S rDNA was studied by means of fluorescence in situ hybridization(FISH)on metaphase chromosomes of different ploidy Citrus grandis.NOR loci of different materials showed obvious polymorphism and heterozygosity.There were four 45S rDNA loci in diploid,while there were ten loci in tetraploid t1 and eight loci in tetraploid t2.Chromosomal location of rDNA loci included five types,i.e.the telomeric region of the short arm,centromere to the short arm region,the centromeric region,centromere to the long arm region,the telomeric region of the long arm.Different materials had incomplete same rDNA loci types.The number of loci was not the same in different situations,the most were types of centromere to short arm region and centromeric region,next was the telomeric region of the short arm.There was a variation in DNA among the homologous tetraploids with the corresponding diploid.Meanwhile,the citrus chromosome slides used for FISH and rDNA loci situation on chromosome,genetic variation analysis among the homologous tetraploids and diploids,repeated sequence of chromosome in situ hybridization(CISH)for chromosome identification and species evolvement were discussed.