桂花(Osmanthus fragrans)高密度分子遗传图谱的构建

Widely known for its strong aroma, Osmanthus fragrans is one of China's top ten ornamental plants and has values far beyond the merely decorative. A native of the substropics, O. fragrans grows well in temperate regions only when suitable micro-climatic conditions are provided. However, breeding and genetic researches on O. fragrans have not been adequately funded. While some new varieties have been created using mutated buds, cold resistant cultivars remain an unreached goal to date. Horticultural production urgently requires a physiologically diverse array of high-quality O. fragrans strains. The present project seeks to apply the hybrid vigor principle to the breeding of new O. fragrans cultivars. Distantly related strains obtained from previous studies will be hybridized to produce F1 seeds. We will then graft branches from field-grown F1 seedlings to Chionanthus retusus plants, thus establishing large monoclonal strains. Subsequently, we shall determine those strains' cold resistance potentials by observing their morphological traits and measuring their physiological/physiochemical parameters in the field, hence laying foundations for selecting suitable O. fragrans cultivars and locating agronomically important quantitative trait locus (QTL). Furthermore, we shall construct the first high-density molecular genetic map of O. fragrans by using the AFLP, SSR, SRAP, and SCoT techniques, within the double pseudotestcross format framework, to analyze F1 plants. Aside from meeting the market's need for high-quality O. fragrans cultivars, this study may also provide a useful technological platform for a variety of future endeavors, including the search for major genes controlling quantitative traits, applying such knowledge to molecular marker assisted breeding of O. fragrans, early selections of cultivars, compressing breeding cycles, and improving the efficiency of breeding programs.

:桂花是我国十大名花之一，著名芳香源植物，观赏和实用兼备。主要分布在亚热带以南，在温带地区仅在小气候中生长良好。桂花育种和遗传学研究滞后，仅靠芽变选育了一些品种，尤其是抗寒育种更是空白，生产上急需满足不同需要的桂花良种。本项目拟根据杂交优势原理，在本课题组已构建的核心种质内，选择亲缘关系较远的品种杂交，获得F1代种子，播种后嫁接扩繁，建立株系。一方面，通过田间性状观察和生理生化指标测定，从两方面评价每个株系的抗寒能力，为适合不同需要的桂花品种的选择和重要农艺性状的QTL定位打下基础。另一方面，根据双假测交理论，以F1代为构图群体，用AFLP、SSR、SRAP、SCoT四种分子标记构建第一张桂花高密度分子遗传图谱。此项研究可以直接选育适合市场需要的优良品种，同时为下一步寻找控制数量性状主效基因，并将其应用到桂花分子标记辅助育种，实现早期选择，缩短育种周期，提高育种效率提供技术支撑。

桂花(Osmanthus fragrans Lour.)是中国的十大传统名花，具有多种实用价值，深受人们的喜爱和研究者的关注。到目前为止，桂花的遗传图谱尚未见报道。本项目采用特异性长度扩增片段测序（SLAF-seq）技术成功构建了桂花的第一张高密度连锁图谱，为其进一步研究提供依据。通过对亲本和129个F1单株进行简化基因组测序，获得206.92M的双端reads，聚类分析后共形成173,537 个SLAF标签，其中90,715个具有多态性，占总数的 52.27% ，对多态性标签进行基因型分析，过滤掉父母本信息缺失、完整度过低、和不适合F1群体作图的多态性标签，最终获得15,317 个有效标记，按照分离类型，最终选择了14,189 个SLAF标记用于F1群体分析，其中母本信息来源位点4,514个，父本来源位点6,993个，双亲信息来源位点2,682个，卡方检验结果显示有950个位点的基因型频率偏离预期的孟德尔定律。采用“拟测交”策略分别构建双亲遗传图谱，其中母本遗传图谱包含23 个连锁群，9,175个SLAF标记，总覆盖遗传距离2,952.2cM ，平均图距0.31 cM，连锁群长度范围79.84cM- 319.5cM；父本遗传图谱包含7,196个标记，分属于23 个连锁群，图谱总长2,872.91cM，平均图距为0.4 cM，连锁群长特范围94.67cM -184.81；利用同源位点进行双亲图谱整合，最终得到的整合图谱共23 个连锁群，与桂花染色体数一致，包含14,189个SLAF标签，图谱覆盖基因组长2,962.46cM，相邻标记间最大距离 9.35 cM，最小间距 0.17 cM，平均图距为0.21 cM，连锁群长特范围92.87cM -252.15 cM。. 该项目构建了桂花首张高密度的遗传图谱，为以后目标性状的基因定位研究奠定了基础；同时，项目组还对桂花的花色和花香产生的分子机理及其调控进行了的研究。这些研究结果为桂花基因组结构与功能的研宄、相关基因的图位克隆、分子标记辅助选择育种奠定了坚实的基础。