基于nSSR和cpDNA序列的城步峒茶群体遗传多样性和结构研究

Genetic Diversity and Structure of Chengbudong Tea Population Revealed by nSSR and cpDNA Markers

采用简单重复序列标记(nSSR)与叶绿体DNA序列(cpDNA)分析技术,对城步峒茶群体进行了遗传多样性、遗传结构和遗传分化等研究。结果表明,15对nSSR引物在参试81份资源中共获得142个等位位点,平均每对引物9.47个,城步峒茶群体的观测杂合度(Ho)、期望杂合度(He)和Nei期望杂合度(Nei)分别为0.49、0.62和0.62,具有较高的遗传多样性。Structure分析将79份峒茶资源分成3个类群,但各类群的遗传背景较为复杂,没有明显的群体结构。F检验表明,城步峒茶群体的近交系数FIS为正值(FIS=0.1775),群体间的遗传分化系数FST较小(FST=0.0345),分化程度较低,基因流Nm较高(Nm=7.01)。3对cpDNA引物分别获得了473 bp(rbc L)、704 bp(mat K)和320 bp(psb H-trn A)的片段序列,变异位点占总位点的比例分别为0.42%、0.71%和1.25%。将3个序列依次拼接,共产生了9个单倍型,单倍型数由多到少的居群依次为TXZ(6)、DZC(4)、DPS(4)、TYS(3)、HJZ(2),群体的单倍型多样性(Hd)和核苷酸多样性(π)分别为0.732和0.00139。9个单倍型中,单倍型H1和H5处于进化网络图的中心节点上,并且包含资源数量最多,属于比较原始的单倍型。同时,nSSR和cpDNA的AMOVA分析结果基本一致,居群内的变异百分比分别达到96.69%和80.54%,城步峒茶的遗传变异主要存在于居群内。

The 81 accessions were detected by 15 nuclear SSR and 3 cpDNA markers. A total of 142 observed number of alleles were detected, and the expected homozygosty(Ho), expected heterozygosity(He), Nei’s expected heterozygosity(Nei) of Chengbudong tea were 0.49, 0.62 and 0.62, respectively, suggesting Dong tea had a high genetic diversity. The STRUCTURE software was applied to the nSSR data to infer the genetic structure in the 79 Chengbudong tea accessions. When K=3, the Delta K value was maximized, but the five populations belonged to a mixed population without any clear genetic structure. F test showed that the inbreeding coefficient of Chengbudong tea was positive(FIS=0.177 5). Genetic differentiation coefficient FST was 0.034 5, indicating a low degree of differentiation and high gene flow(Nm=7.01). The aligned chloroplast DNA sequences of rbc L, mat K and trn H-psb A were 473 bp, 704 bp, 320 bp in length. The polymorphic site percentages were 0.42%, 0.71% and 1.25%, respectively. A total of 9 haplotypes(H1-H9) were identified across the 81 tea accessions including two outgroup accessions. TXZ population had the highest haplotypes(6), followed by DZC(4), DPS(4), TYS(3) and HJZ(2). The total haplotype diversity(Hd) and nucleotide diversity(π) were 0.732 and 0.001 39, respectively. Among 9 cpDNA haplotypes, haplotypes H1 and H5 were the ancestral haplotypes. The sources of genetic differentiation were revealed within and among populations by the AMOVA method. The results of nSSR and cpDNA analysis were basically consistent, with variations within populations of 96.69%(nSSR) and 80.54%(cpDNA), respectively.