利用位于45S rDNA内转录间隔区(ITS)的3对SSR引物,对山茶属(Camellia L.)的40个物种进行PCR扩增,检测3个SSR位点的多态性,研究物种倍性与多态性之间的关系.实验结果显示,37个种(占92.5%)的ITS片段存在个体内长度多态性,在这些种类的个体内至少有2-6类ITS拷贝,表明山茶属植物的ITS片段存在广泛的非一致性进化;ITS序列上存在易于滑动的SSR位点,并且其基因组中有较多位于不同染色体上的rDNA位点,这很可能是山茶属植物ITS片段存在广泛多态性的原因.然而,研究中没有发现多倍体种类ITS片段的多态性显著高于二倍体种类.山茶属植物ITS片段的多态性提示该属植物的rDNA可能存在更为复杂的进化模式,在利用ITS片段解决该属植物的系统分类问题时应更为谨慎.%In this study, we used 3 pairs of simple sequence repeat (SSR) markers from the 45S rDNA internal transcribed spacer (ITS) for PCR amplification in 40 species of Camellia to detect polymorphism in Camellia and the relationship between ploidy and polymorphism of species. In total, 37 species (92.5％) exhibited length polymorphism within individuals. At least 2-6 types of the ITS copies were found in individuals of these species, which indicates that non-concerted evolution is common in the ITS fragments in Camellia. Extensive non-concerted evolution may have resulted from SSR loci, which slip easily in the ITS region, and multiple rDNA loci that are located on different chromosomes. However, we did not find a significant difference in polymorphism between polyploidy and diploid. The polymorphism of the ITS region in Camellia species shows that there may be a more complex model of evolution in the rDNA of the genus, so the ITS sequences should be used with caution in solving the systematics problems of the genus.
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