基于cpDNA和rDNA ITS片段分析西南地区青杨派杨树的系统发育与进化关系

西南地区青杨派杨树种质资源丰富,可为杨树遗传改良提供珍贵的基因资源,但树种之间形态学差异细微,该研究以山杨作为外类群,测定了西南地区及其他地区杨属青杨派17个种(杂种)共36份样本的3个叶绿体片段(atpF-atpH、trnL-F和matK)和核糖体ITS片段,并对其进行系统发育分析,以探讨西南地区青杨派树种的系统进化关系。结果表明:(1)在所有样本中,3个叶绿体片段atpF-atpH、trnL-F、matK的长度分别为605~634bp、957~1 010bp、819bp,3个片段拼接后的联合序列包含29个变异位点和15个信息位点;ITS片段对齐后的长度为646bp,变异位点19个,信息位点17个。(2)基于叶绿体联合序列和ITS片段的杨属青杨派树种的平均遗传距离分别为0.001 3和0.003 6。叶绿体联合片段的MP和Bayes系统树树型基本一致,青杨派树种可以划分为2组,第1组由青杨、三脉青杨、大青杨和辽杨构成;第2组中的小叶杨、小青杨、川杨、德钦杨、昌都杨、乡城杨、康定杨、西南杨、滇杨和藏川杨不能有效区分,且均与缘毛杨的遗传关系较近。(3)基于ITS的系统树与叶绿体联合片段构建的系统树差异不大,仅在于第2组中的小青杨与小叶杨、川杨等差异明显,与第1组中的树种紧密聚拢。

Phylogeny of Poplar in Section Tacamahaca Species from Southwest China Based on Sequence Data of cpDNA Fragments and rDNA ITS

Despite abundant germplasm resources in Southwest China for poplar genetic improvement,the varied species exist tiny difference in morphology and have unknown systematic relationship.Using Populus davidiana as outgroup,the phylogenetic relationship of 36 specimens covering 17 species or hybrids collected from Southwest China and other areas was explored based on sequence data of chloroplast atpF-atpH,trnL-F,matK and nuclear ITS.The results showed that:(1)the ranges of length in atpF-atpH,trnL-F and matK were 605-634 bp,957-1 010 bp and 819 bp respectively,and the combination of 3 chloroplast fragments had 29 variable sites and 15 informative sites,while the aligned length of ITS fragment including 19 variable sites and 17 informative sites was 646 bp.(2)The average genetic distance among all samples of chloroplast combination was 0.001 3 and that of ITS fragment was 0.003 6.Based on chloroplast combination data,the result of MP tree was consistent with that of Bayesian algorithms and both suggested the Populus section Tacamahaca species were divided into 2 clades,of which,clade 1 was formed by P.cathayana,P.trinervis,P.ussuriensis,P.maximowiczii,and the species in clade 2,namely,P.simonii,P.pseudo-simonii,P.szechuanica,P.haoana,P.qamdoensis,P.xiangchengensis,P.kangdingensis,P.schneideri,P.yunnanensis,P.szechuanica var.tibetica,could not be clearly separated and had close relationship with P.ciliata.(3)Although a few differences in phylogenetic tree based on chloroplast combination data,ITS fragment provided that P.pseudo-simonii existed closer affinity with other species in clade 1 (e.g.P.simonii and P.szechuanica) but larger genetic distance with others in clade 2.The results of this study made a understand on the phylogeny of poplar in section Tacamahaca species from Southwest China,and provided a scientific bases for their systematic classification and evolutionary relationship.