【作者】 王祎玲；

【导师】 赵桂仿；

【作者基本信息】 西北大学 ， 植物学， 2003， 硕士

【摘要】 叉毛蓬（Petrosimonia sibirica）属于藜科叉毛蓬属，一年生草本植物，仅分布在我国新疆地区的北部。叉毛蓬植物是叉毛蓬属中较为进化的一类。目前对叉毛蓬的研究很少，本文试图运用RAPD分子标记技术研究叉毛蓬居群的遗传结构和遗传分化，并且探讨其与生境的相关性，为探明荒漠植物的遗传背景、系统演化及制定保护策略提供科学依据。 研究结果表明：用2×CTAB法提取叉毛蓬居群的总DNA，效果良好，提取物可用于随后的RAPD遗传多样性分析。通过优化的RAPD反应体系可以得到清晰、稳定可重复性高的扩增带。用RAPD分子标记对叉毛蓬5个亚居群共98个个体进行了遗传多样性检测，14个10碱基寡聚核甘酸引物共检测到77个位点，其中多态位点76个，多态位点比率为98.7％。亚居群2的多态位点比率最大，亚居群5的多态位点比率最小。按所检测的多态位点比率排列各亚居群的顺序为：亚居群2＞亚居群1＞亚居群4＞亚居群3＞亚居群5。多态位点比率结果表明叉毛蓬居群的遗传多样性水平较高。 利用Shannon多样性指数估计5个亚居群的遗传多样性，叉毛蓬亚居群内和亚居群间的遗传多样性所占的比例分别为69.33％和30.67％，遗传变异大部分存在于亚居群之内。又利用Neis指数估计叉毛蓬居群的遗传多样性，也表明大部分的分子变异存在于亚居群之内（69.48％）。但叉毛蓬亚居群的遗传分化系数(G_ST)为0.3052，说明亚居群间已有明显的遗传分化发生。5个亚居群间的遗传距离的矩阵显示亚居群2与亚居群4的遗传距离最大，亚居群1与亚居群2的遗传距离最小，分别为0.2445和0.1258，亚居群间的平均遗传距离为0.1664，也说明5个亚居群之间产生了遗传分化。 叉毛蓬亚居群的基因流N_m=1.138，低于一般广布种的基因流水平（N_m=1.881），且远低于毛乌素沙地柠条的基因流（N_m=5.9529），相对有限的基因流可能在叉毛蓬居群遗传分化的维持中起着作用。 根据RAPD数据对叉毛蓬98个个体进行Ward聚类分析，结果可将98个个体都能区分开，5个亚居群都有明显以彼此为中心聚集的趋势，说明各亚居群间已有不同程度的遗传分化。亚居群4、5最先聚合，表明亚居群个体间的一致度较高，异质性较低。这可能是由于亚居群4、5所处环境的相对一致性；亚居群1、2也是由于所处环境的相对一致性，之后聚为一支。最后，亚居群3与其他居群聚为一类，表明个体间的差异较大，这可能是由于各个个体所处的微生境各不相同所致。 用PCA法分析了叉毛蓬的遗传变异与生境的关系。结果表明:98个个体在前三个主分量中占总信息量的62.9既。第一主分量包含的信息量为28.53%，第二主分量包含的信息量为21.32%，第三主分量包含的信息量为13.05%。X轴为第一主分量，98个个体的投射点分别集中在四个区间在一2^一1区间以亚居群1为主，一1⁰区间以亚居群2为主，O一1区间以亚居群3、4为主，1³区间以亚居群5为主。从个体在x轴的梯度变化规律来看，基本上反映了水分、养分的关系。Y轴为第二主分量，从Y轴上个体的投射点的分布梯度来看，基本上反映了经度变化的趋势。Z轴为第三主分量，从个体的投射点看，5个亚居群集中在两个区间内，在一定程度上反映了土壤中易溶性盐分变化的规律。 相关分析结果表明，叉毛蓬居群的遗传多样性指标与土壤中的易溶性盐分呈显著负相关（尸<0.05），表明易溶性盐分在维持叉毛蓬亚居群遗传多样性方面可能起着一定的作用。与土壤中的水分呈不相关关系（尸>0.05），但遗传距离却与水分呈显著相关（尸<0.05），说明水分在叉毛蓬植物的分布上可能起着作用，但在长期的适应干早环境过程中，叉毛蓬植物可以利用土壤中有限的水分，完成它的生活史。同时，环境因子与叉毛蓬居群中的某些等位基因频率的相关性显著（尸<0.05），说明这些位点对环境因子比较敏感。环境因子的变化引起了基因频率的变化，表明环境因子差异在叉毛蓬居群的遗传分化中起着一定的作用，即环境因子差异导致的选择差异可能在遗传分化中起着作用。另外，研究表明叉毛蓬5个亚居群的遗传距离与空间距离没有显著的相关关系，表明空间距离在叉毛蓬居群的遗传分化贡献中不起作用。 综合上述研究，可得出以下结论:①叉毛蓬居群的遗传多样性水平较高，可以适应不断变化的环境压力。②叉毛蓬居群间产生了一定的遗传分化和分子变异，遗传分化的产生可能由于亚居群间相对有限的基因流和亚居群所处的微环境不同所致。③叉毛蓬亚居群已经表现出对局部微生境的适应，成为过渡带上稳定发展的亚居群。更多还原

【Abstract】 Petrosimonia sibirica, which belonged to Petrosimonia Bunge in Chenopodiceae, was a kind of ephemeretum and only distributed in Xinjiang of China. This thesis is mainly studying the genetic structure and variation of P. sibirica with RAPD and the correlation with the surrounding environmental factors. And the survey provide the accurate and scientific information for understanding the genetic background systematic evolutionary of the desert plants and planning the effective conservation strategy.With 2+CTAB method, we can successfully extract total DNA from the leaf tissues of P. sibirica. By a series of tests, we obtained an economic and effective RAPD reaction system for adapting to P. sibirica RAPD markers. The optimized system included 0.1U Taq DNA polymerase, 1.5μl buffer (1+), 2μl Mg2+(2.5mM), 0.6μl dNTP (0.3μM), 8μl primer (12μM), 8ng temlpate DNA, 5.6μ1 ddH2O.The genetic diversity of P. sibirica, which is represented by 98 individuals collected from all 5 subpopulations, investigated with RAPD markers. 77 loci were selected by fourteen 10-mer primers, of which 76 were polymorphic. The percentage of polymorphic loci (PPB) of five subpopulations was 70.13%, 77.99%, 62.34%, 67.53%, and 61.04% respectively. The higher PPB (77.99%) was in subp.2 and lower (61.04%) in subp.5. The PPB’s order was subp.2> subp.l> subp.4> subp.3> subp.5. The result revealed higher genetic diversity level in P. sibirica.By Shannon phenotypic diversity index from RAPD data, it was found that 69.33% of molecular variation existed within subpopulations while 30.67% of which among subpopulations. The result with Nei’s index also identified it. And the genetic differentiation coefficient was 0.3052, which showed the genetic differentiation had occurred among subpopulations of P.sibirica in the oasis-desert zone. The genetic average distance among five subpopulations of P.sibirica was 0.1664; the largest was 0.2445 between subp.2 and subp.4, and the smallest was 0.1258 between subp.l and subp.2. It also showed the genetic variation existed among the subpopulations.Moreover, the gene flow of P. sibirica population (Nm=1.138) was lower than that of cosmopolite species (Nm= 1.881), and much lower than that of Caragana spp. populations over Maowusu sandy grassland (Nm =5.9529). It suggested that relativelylimited gene flow might be one of important factors influencing on the genetic structure of the species.In addition, through the correlation analysis, we observed the correlation between the genetic distance of P. sibirica and latitude, longitude and altitude was not significant. It showed the geographical difference was not one of the potential factors, which affected the genetic differentiation of P. sibirica.The cluster analysis could classify 98 individuals into 5 centers by Ward’s method. It also showed there were some differentiations among subpopulations. The individuals within subp.4 were clustered firstly into one group as well as subp.5 In fact, because of the similarity of the environment, subp.4 and subp.5 had the same genetic characteristics. And then subp. 1, subp.2 was clustered. Lastly, the individuals of subp.3 were clustered, which indicated the greater genetic differentiation among those individuals.The relationship between molecular variation and habitat of P. sibirica was shown by PCA analysis with RAPD data. At the first principle axis(X-axis), 98 individuals concentrated on four region: subp.1 was mainly distributed at -2-1 range, subp.2 at -1-0, subp.3 and subp.4 at 0-1, subp.5 at 1-3. It revealed the distribution of the individuals related to the soil water and nutrition. And similarly, P. sibirica individuals scatter at the second principle axis (Y-axis), which representing the altitude and latitude. All individuals were focused on two zones at the third principle axis (Z-axis), which showed the distribution of soluble salt in soil.At the same time, the soluble salt in soil of the oasis desert transitional zone might play a role in maintaining the genetic diversity of P. sibiri更多还原