野生胡萝卜（Daucus carota ssp. carota）种群中的历史和当代基因扩散。
Historical and contemporary gene dispersal in wild carrot (Daucus carota ssp. carota) populations.
机构信息
Institute of Biology Leiden, Leiden University, The Netherlands.
出版信息
Ann Bot. 2010 Aug;106(2):285-96. doi: 10.1093/aob/mcq108. Epub 2010 Jun 21.
BACKGROUND AND AIMS
Wild carrot is the ancestor of cultivated carrot and is the most important gene pool for carrot breeding. Transgenic carrot may be released into the environment in the future. The aim of the present study was to determine how far a gene can disperse in wild carrot populations, facilitating risk assessment and management of transgene introgression from cultivated to wild carrots and helping to design sampling strategies for germplasm collections.
METHODS
Wild carrots were sampled from Meijendel and Alkmaar in The Netherlands and genotyped with 12 microsatellite markers. Spatial autocorrelation analyses were used to detect spatial genetic structures (SGSs). Historical gene dispersal estimates were based on an isolation by distance model. Mating system and contemporary pollen dispersal were estimated using 437 offspring of 20 mothers with different spatial distances and a correlated paternity analysis in the Meijendel population.
KEY RESULTS
Significant SGSs are found in both populations and they are not significantly different from each other. Combined SGS analysis indicated significant positive genetic correlations up to 27 m. Historical gene dispersal sigma(g) and neighbourhood size N(b) were estimated to be 4-12 m [95 % confidence interval (CI): 3-25] and 42-73 plants (95 % CI: 28-322) in Meijendel and 10-31 m (95 % CI: 7-infinity) and 57-198 plants (95 % CI: 28-infinity) in Alkmaar with longer gene dispersal in lower density populations. Contemporary pollen dispersal follows a fat-tailed exponential-power distribution, implying pollen of wild carrots could be dispersed by insects over long distance. The estimated outcrossing rate was 96 %.
CONCLUSIONS
SGSs in wild carrots may be the result of high outcrossing, restricted seed dispersal and long-distance pollen dispersal. High outcrossing and long-distance pollen dispersal suggest high frequency of transgene flow might occur from cultivated to wild carrots and that they could easily spread within and between populations.
背景与目的
野胡萝卜是栽培胡萝卜的祖先，是胡萝卜育种最重要的基因库。未来可能会将转基因胡萝卜释放到环境中。本研究旨在确定基因在野胡萝卜种群中的扩散距离，从而促进对栽培胡萝卜向野生胡萝卜基因渗入风险的评估和管理，并有助于设计种质资源收集的采样策略。
方法
从荷兰的 Meijendel 和 Alkmaar 采集野胡萝卜样本，并使用 12 个微卫星标记进行基因型分析。采用空间自相关分析来检测空间遗传结构（SGS）。历史基因扩散估计是基于距离隔离模型。通过 20 个具有不同空间距离的母本的 437 个后代和 Meijendel 群体中的相关父系分析，估计交配系统和当代花粉扩散。
结果
在两个种群中都发现了显著的 SGS，且彼此之间没有显著差异。综合 SGS 分析表明，在 27 米的范围内存在显著的正遗传相关性。在 Meijendel，历史基因扩散 sigma(g)和邻居大小 N(b)分别估计为 4-12 米（95%置信区间[95%CI]：3-25）和 42-73 株（95%CI：28-322），在 Alkmaar 分别为 10-31 米（95%CI：7-infinity）和 57-198 株（95%CI：28-infinity），在密度较低的种群中基因扩散距离较长。当代花粉扩散遵循长尾指数幂分布，意味着野胡萝卜的花粉可能通过昆虫远距离传播。估计的异交率为 96%。
结论
野胡萝卜中的 SGS 可能是由于高度异交、限制的种子扩散和长距离花粉扩散所致。高异交和长距离花粉扩散表明，从栽培胡萝卜向野生胡萝卜发生转基因流的频率可能很高，它们可以在种群内和种群间轻易传播。
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