石斛属植物rDNA ITS序列的克隆与分析

对24种石斛属植物的rDNA ITS序列进行克隆分析，以期为石斛属植物的分子鉴定和遗传多样性研究提供依据。以叶片基因组为模板，利用通用引物分别扩增24种石斛属植物的ITS序列，结果表明，ITS全长为634～646 bp，其中，58S序列的长度十分保守，均为164 bp；而ITS1和ITS2序列长度变异较大，分别为226～235 bp和241～247 bp。ITS1和ITS2序列具有丰富的变异位点，分别为176和166个；其中，信息位点分别为114和104个，发现了大量的转换、颠换和插入/缺失现象。而58S序列相对保守，有36个变异位点，其中信息位点16个。本研究表明，利用ITS序列可将本研究中的24种石斛属植物完全区分，这24种石斛属植物的遗传距离为0007～0302，其中鼓槌石斛和粟斑鼓槌石斛的遗传距离最小，亲缘关系最为接近；而金耳石斛与短棒石斛的遗传距离最大，亲缘关系最远。

Cloning and analysis of rDNA ITS sequences from Dendrobium plants

In the present study， ITS sequences were cloned from 24 Dendrobium plants， and were analyzed by bioinformatics software to provide evidences for molecular identification and genetic diversity study. The full ITS sequences of 24 plants ranged from 634-646 bp in length. Sequences of 58S were conserved with the same length of 164 bp， while ITS1 and ITS2 were more variable with lengths of 226-235 bp and 241-247 bp， respectively. Variable sites were rich in ITS1 and ITS2 sequences， as there were 176 and 166 variable sites with 114 and 104 parsimony information sites， respectively， and many transitions， transversions， and deletions/insertions were observed. However， 58S sequences were more conserved， and there were 36 variable sites and 16 parsimony information sites. It was shown that ITS sequences could be used to distinguish all 24 Dendrobium plants studied here. The genetic distance of 24 Dendrobium plants ranged from 0007 to 0302. The smallest genetic distance was observed between D. chrysotoxum and D. chrysotoxum var. suavissimum revealing their closest relationship， while the largest genetic distance was determined between D. hookerianum and D. capillipes uncovering their distinct relationship.