石山苣苔属四种(含一变种)植物的染色体数目和倍性研究

石山苣苔属(苦苣苔科)约41种,主要分布于我国西南石灰岩地区。到目前为止,仅其中四种的染色体数目被研究和报道,其余绝大多数物种的染色体数目和倍性尚不清楚,染色体数目和倍性在该属及其姐妹属报春苣苔属中的演变历史及其对两属物种多样性分化的影响亦不清楚。该文以叶片水培生根法获取的四种(含一变种)石山苣苔属植物 即石山苣苔原变种(Petrocodon dealbatus var. dealbatus)、齿缘石山苣苔(Petrocodon dealbatus var. denticulatus)、弄岗石山苣苔(Petrocodon longangensis)、石山苣苔未定名种(Petrocodon sp.)]的根尖细胞为材料开展染色体实验,探索了多种不同的实验条件对染色体制片效果的影响并获取染色体数目,在石山苣苔属和报春苣苔属的系统树上追踪了染色体数目和倍性的演变历史,同时探讨染色体数目尤其是倍性变化是否对两属物种多样性分化存在影响。结果表明:(1)长度为1～1.5 cm的根尖,0.002 mol·L^-1 8-羟基喹啉溶液预处理5 h,解离4 min为较适宜的染色体制备条件。(2)四种(含一变种)石山苣苔属植物染色体数目一致,均为二倍体(2n=2x=36)。(3)两属之间及两属各自的最近共同祖先染色体数目尚不能确定,除个别物种染色体条数或倍性有变化以外,其余已知染色体数目的物种均为2n=2x=36,在两属中高度一致,石山苣苔属与报春苣苔属物种多样性分化尤其两属物种多样性巨大差异与染色体数目和基因组倍性变化无关。综上结果为石山苣苔属植物及其近缘类群染色体制备提供了参考,也为进一步对该类群的分类、系统演化和物种形成等方面的研究提供了基础数据和启示。

Chromosome numbers and ploidy of four species (including one variety)in Petrocodon Hance

Petrocodon Hance(Gesneriaceae)consists of 41 species and is mainly distributed in the limestone region of South China. So far, the chromosome numbers of only four species have been reported, with the rest species in the genus remained uninvestigated yet. Furthermore, the evolutionary history of the chromosome number and ploidy in Petrocodon as well as in its sister genus Primulina remain unexplored, and particularly whether it affected their diversifications into extant species diversity remain unknown. In this study, the root tip cells of four species(including one variety)of Petrocodon(i.e. Petrocodon dealbatus var. dealbatus, Petrocodon dealbatus var. denticulatus, Petrocodon longangensis and Petrocodon sp.)which were generated by hydroponic culture method for the cutting leaves, were used for the chromosome experiments. First, the effects of various experimental treating conditions on the quality of chromosome squashing were explored and the chromosome numbers were counted. Then, the evolutionary history of chromosome numbers in Petrocodon and Primulina were traced based on the molecular phylogenetic tree, and whether the diversifications of the species diversity for the two genera were impacted by changes of the chromosome number or especially the ploidy or not was discussed. The results were as follows:(1)The root tip of 1-1.5 cm length, pretreatment for 5 h with 0.002 mol·L^-1 8-hydroxyquinoline solution and dissociation for 4 min was a suitable chromosome preparation condition.(2)All the four species(including one variety)investigated were diploid and the chromosome numbers were the same(2n=2x=36).(3)Although the reconstruction of the ancestral state of the chromosome number of Petrocodon and Primulina failed to give any resolution for the most recent common ancestors of the two genera(generic stem node)and each of the genera(generic crown nodes), the chromosome number of Petrocodon and Primulina was highly conserved with most taxa possessing 2n=2x=36, except for the ploidy or chromosome number changes in few species, suggesting the disproportional diversification of species diversity between Petrocodon and Primulina was not correlated to the change of the chromosome number or ploidy. This study provides a reference for the chromosome preparation of Petrocodon and its allies, and also provides basic data and implications for further research on the classification, systematic evolution and speciation of Petrocodon