基于ITS 序列探讨沙棘属植物的系统发育关系

对分布于青海境内的中国沙棘、肋果沙棘和西藏沙棘的ITS区进行扩增和序列分析，并以胡颓子科胡颓子属沙枣为外类群，对胡颓子科沙棘属15种植物的ITS序列进行聚类分析, 探讨沙棘属各植物的亲缘关系.结果表明： 3种沙棘属植物的ITS区长度为600～605 bp，其中，ITS-1区为201～203 bp，5.8S为166～167 bp，ITS-2区为232～236 bp.核苷酸分析显示，3种沙棘属植物的ITS区存在丰富的变异位点.聚类分析表明，棱果沙棘种的2个亚种——棱果沙棘和理塘沙棘为2个不同种，江孜沙棘与柳叶沙棘之间的亲缘关系较近，而与中国沙棘亲缘关系较远；沙棘种下9个亚种间的聚类结果与形态学分类差异较大.

Phylogenetic relationships of seabuckthorn based on ITS sequences.

Sequences of the internal transcribed spacer (ITS) was compared in three seabuckthrons (Hippophae rhamnoides subsp. sinensis, H. tibetana and H. neurocarpa) distributed in Qinghai Province, then the systematic positions of 15 seabuckthron samples were analyzed with Elaeagnaceae angustifolia being outgroup. The results showed that ITS sequences in three seabuckthron species varied in length from 600 to 605 bp. ITS-1, 5.8S and ITS 2 varied from 201 to 203 bp, 166 to 167 bp and 232 to 236 bp, respectively. The sequence divergence among three seabuckthorn species was also remarkably high. Cluster analysis based on ITS indicated that H. gonicocarpa subsp. litangensis and H. gonicocarpa subsp. goniocarpa were distinct and could be classified as H. gonicocarpa and H. litangensis. H. gyantsensis had the closest genetic relationship with H. salicifolia and the distant relationship with H. rhamnoides subsp. sinensis. The positions of nine subspecies of H. rhamnoides based on morphological classification were different from the results of ITS.