野生荔枝基因组水平遗传多样性及中国栽培荔枝的起源研究

As the ancestor population of cultivated litchi (Litchi chinensis Sonn.), wild litchi is valuable gene resources for research of domestication process and genetic improvement of cultivated litchi. However, deforestation and overexploitation have greatly reduced the wild litchi populations in the past several decades, and now it is listed as an endangered species in China. In this study, accessions of wild litchi in southern China and northern Vietnam which represented the species-wide distribution and cultivated litchi in China are genotyped with single nucleotide polymorphism (SNP) markers that are spread evenly over the litchi genome. Based on population genetic analysis of the genotyped SNP data, genome-wide patterns of genetic diversity and population structure of wild litchi throughout its natural range are investigated; the phylogenetic relationship of the wild and cultivated litchi are also studied to elucidate the domestication origin of litchi. Genome scan for signature of selection using these SNP data are employed to identify candidates for selectively important genes that may have been involved in the local adaptation of wild litchi and domestication process of cultivated litchi. Knowledge of population genetics, domestication origin as well as genetics basis of local adaptation and domestication process is of great importance for the effective conservation and utilization of the wild litchi germplasm and to facilitate the genetic improvement of cultivated litchi.

野生荔枝是栽培荔枝的祖先群体，是栽培荔枝品种改良的重要基因来源，是研究荔枝起源、演化和遗传育种的宝贵资源。但近年来野生荔枝资源面临灭绝的危险，现已被列为国家二级保护植物。本项目拟对野生荔枝全分布区域即中国和越南的群体以及中国栽培荔枝主栽省份的地方品种进行取样，利用均匀分布在荔枝全基因组的SNP标记揭示野生荔枝在基因组水平上的遗传多样性、遗传分化模式及地理分布格局；同时进行野生荔枝与栽培荔枝的亲缘关系分析，探讨栽培荔枝的起源式样和驯化历史。此外，对野生荔枝全分布范围的群体进行全基因组扫描，结合与各地生态环境因子的相关性分析，发掘与野生荔枝地方适应性相关的异常位点和环境因子；同时对野生荔枝和栽培荔枝对比进行全基因组扫描，发掘与栽培荔枝驯化过程相关的异常位点。研究结果将为野生荔枝的合理保护和可持续利用提供科学依据，为加速荔枝品种改良提供理论指导，为荔枝品种的种质创新提供新的有益基因资源。

野生荔枝是栽培荔枝的祖先群体，是栽培荔枝品种改良的重要基因来源，是研究荔枝起源、演化和遗传育种的宝贵资源。但近年来野生荔枝资源面临灭绝的危险，现已被列为国家二级保护植物。本研究对中国野生荔枝全分布区域的群体和栽培荔枝主栽省份的地方品种进行取样，利用均匀分布在荔枝全基因组的SNP标记揭示野生荔枝的遗传分化模式及地理分布格局；同时进行野生荔枝与栽培荔枝的亲缘关系分析，探讨栽培荔枝的起源式样和驯化历史。此外，对野生荔枝和栽培荔枝对比进行全基因组扫描，发掘与栽培荔枝驯化过程相关的异常位点；同时对不同成熟期的荔枝品种对比进行全基因组扫描，发掘与栽培荔枝成熟期相关的异常位点。研究结果表明，中国的野生荔枝在遗传上可分为两大类群，广西大新和云南的野生荔枝为一个类群，而广西博白、广东及海南的野生荔枝则是另外一个类群。中国的栽培荔枝应为多点独立驯化起源，其中特早熟品种由广西大新-云南野生荔枝驯化而来，中晚熟品种由广西博白-广东-海南野生荔枝驯化而来，而早熟品种则很可能是杂交起源而来。发掘了栽培荔枝驯化相关和熟期相关的异常位点，其中有部分基因获得了很好的功能注释，是进一步功能研究的候选基因。研究结果为野生荔枝的合理保护和可持续利用提供了科学依据，为加速荔枝品种改良提供了理论指导，为荔枝品种的种质创新提供了新的有益基因资源。