基于细胞学和DNA序列的苎麻与其野生近缘类群系统关系研究

为了了解苎麻与野生近缘种的系统学关系，更有效利用野生苎麻资源，通过细胞学观察和分子标记证据，对中国苎麻与其24个野生近缘类群进行了系统学分析。细胞学结果表明，苎麻间期核形态属于田中分类体系的前染色体型，而其野生近缘种分别属于前染色体型和分散型；苎麻和23个野生近缘物种(其中15个类群的染色体数目为首次报道)中，19个为二倍体(2n=28)，而大叶苎麻组3个类群为三倍体(2n=42)，1个为四倍体(2n=56)，1个为五倍体(2n=70)。ITS序列和trnL-F序列分析表明，苎麻属可分成A(含A₁和A₂亚分支)、B(含B₁和B₂亚分支)和C 3个基本分支。根据分析结果本文提出苎麻属的两条演化路线: (1)前染色体型进化路线A₁→A₂，即腋球苎麻组→苎麻组；(2)分散型进化路线B→C，即腋球苎麻组→帚序苎麻组→序叶苎麻组→大叶苎麻组。

Phylogenetic Relationship of Ramie and Its Wild Relatives Based on Cytogenetics and DNA Sequences

There are 31 species and 12 varieties of Boehmeria Jacq. in China. Boehmeria nivea is an important fiber crop in China and even in East Asia, which has been cultivated for about 4700 years. Because of the dispute in systematic relationship of different sections of Boehmeria among different scholars，the utilization or protection of B. nivea and its wild resources are restricted. In this paper, the karyomorphology of interphase nuclei and chromosome numbers were investigated in 19 species and 5 varieties, while the sequences of nuclearITS and chloroplast trnL-F were analyzed in 18 species and 9 varieties to explore the relationship between B. nivea and its wild relatives, to speculate how and where B. nivea originated and to effectively utilize plant resources of wild ramie. The cytological observation showed that the interphase karyomorphology of 24 taxa of Boehmeria should belong to pro-chromosome type and diffuse type according to the classification system of Tanaka, in which the interphase nuclei of Sect. Tilocnide and Sect. Boehmeria were pro-chromosome type and those of Sect. Zollingeriana, Sect. Phyllostachys and Sect. Duretia were pro-chromosome type and diffuse type. Cytogenetics examinatation of B. nivea and its 23 wild relatives (chromosome numbers of 15 taxa were reported in this paper at the first time) showed that 19 taxa were diploid (2n=28), while three taxa in Sect. Duretia, were triploid (2n=42), one was tetraploid (2n=56) and one was pentaploid (2n=70). Analyses based on ITS and trnL-F sequences indicated that Boehmeria could be divided into three basic branches, A (including A₁ and A₂ sub-branch), B (including B₁ and B₂ sub-branch) and C. Different individuals or clones of B. clidemioides var. diffusa were gathered into different clades, indicating the hybridization and reticulate evolution among species in Boehmeria, andintrogressionbetween B. nivea and B. clidemioides var. diffusa. The wild core species resources of ramie should include both B. nivea and its three varieties and B. malabarica var. leioclada, B. clidemioides var. diffusa, which all should be intensively protected. It was inferred from the results two evolution routes of Boehmeria were: (1) pro-chromosome evolution line: A₂ originated from A₁, that is, Sect. Tilocnide from Sect. Boehmeria, and (2) diffuse evolution line: C originated from B, the order of origination is Sect. Boehmeria→Sect. Zollingeriana→Sect. Phyllostachys→Sect. Duretia. These two evolution routes may both originated from the same ancestor. It was implied based on the morphological traits of interphase nucleus and molecular experiment that the relationship of Sect. Zollongerie, Sect. Phyllostachys and Sect. Duretia was close, and the systematic relationship of these three sections based on morphological traits was not supported by the experimented evidences in cytology and molecular phylogeny in this study.