广西特有珍稀濒危植物小花异裂菊遗传多样性分析

摘要

采用ISSR分子标记技术,对广西特有珍稀濒危植物小花异裂菊6个野生种群的遗传多样性进行了研究。结果表明：10条引物对141个个体共检测到96个位点,其中29个位点具有多态性,多态位点百分率( PPB)为30.21％。在物种水平上,小花异裂菊 PPB 为30.21％, Nei ’ s 基因多样性指数( H )为0.1054, Shannon’s信息指数(I)为0.1546。在种群水平上,PPB 为9％~19％,H 为0.0212~0.0513,I 为0.0339~0.0805。基于Nei’ s遗传多样性分析所得出的种群间基因分化系数Gst＝0.6905,表明种群内的遗传变异为30.95％,种群间的遗传变异为69.05％,小花异裂菊的遗传变异主要存在于种群间。 AMOVA分析结果与前面结果相符。小花异裂菊种群间的基因流( Nm)为0.2242。从遗传距离看,杨堤和兴坪种群的遗传距离最小,为0.0398,白沙和阳朔之间的遗传距离最大,为0.1609。在UPGMA聚类图中,6个种群可分为两组,阳朔和高田为一组,普益、白沙、兴坪、杨堤聚为一组。研究认为小花异裂菊的自交亲和的繁育系统和分布区域的片段化可能是导致种群遗传多样性较低和种群间高遗传分化的主要原因。该研究结果为该物种种质资源的保护提供了科学依据。%Heteroplexis microcephala is an endangered plant only found in karst limestone regions in the Yangshuo County of Guangxi Zhuang Autonomous Region in China. In the present study, ISSR markers were used to evaluate the genetic variation within and among wild populations that were sampled from Guangxi with a goal to collect basic genetic informa￣tion for its conservation. Leaf samples of 141 individuals were collected from six counties. Based on 10 ISSR primers, 96 clear and reproducible DNA fragments were generated. The percentage of polymorphic bands ( PPB) was 30.21%, Nei’ s gene diversity ( H) was 0.105 4, Shannon information index ( I) was 0.154 6 at the species level, and PPB among popu￣lation ranged from 9% to 19%, H ranged from 0.021 2 to 0.051 3, I ranged from 0.033 9 to 0.080 5. High levels of ge￣netic differentiation among the populations (Gst=0.690 5) were detected on the basis of results from POPGENE, which indicated that 69.05% of the genetic variability was distributed among populations, and only 30.95%of the variation ex￣isted within populations. Molecular variance was also examined using AMOVA based on RAPD banding patterns. The va￣riance component found within populations was 27.28%, and a variance of 72.72% was found among populations. Gene flow( Nm) among the population was 0.224 2 indicating that there was a low migration rate between populations. The highest genetic distance based on Nei’ s genetic genetic distance for all population pairs was 0.160 9 between populations BS and YS, while the lowest was 0.039 8 between XP and YD. UPGMA analysis was performed based on genetic similar￣ity ( Jaccard coefficient) . Six populations were clustered into two main groups, one containing populations YS and GT, and the other containing PY, BS, XP and YD. The high genetic variance among populations and the low genetic diversi￣ty within population could be attributed to the breeding system of part self￣compatibility and the limited gene flow among populations of H. microcephala.