丝瓜日开花时间性状主效QTL的精细定位

The difference of daily flowering time between L.acutangula Roxb. and L.cylindrica Roem. is nearly 12 hours, which has a passive impact on the gene flow between them. In order to understand the genetic basis of this phenomenon, the transcriptome sequencing of sponge gourd was carried out in the preliminary project stage, successfully developing 8,523 pairs of EST-SSR markers. Meanwhile, F2 Population was derived from the cross breeding between S304 (L.acutangula) and P93075 (L.cylindrica), a genetic linkage map consisting of 170 EST-SSR markers was provided, and the primary QTL mapping was conducted for the daily flowering time trait of sponge gourd . On the basis of these studies, this research aims to select a major QTL to develop QTL-NIL (near-isogenic line, NIL) for fine mapping by means of repeated backcross and self cross. At the meantime, the genomic BAC libraries will be constructed for sponge gourd, and BAC cloning including target regions will be screened. By means of the molecular markers developed by sequencing BAC cloning, coupled with QTL-NIL, fine mapping of QTL will be conducted. This research is supposed to reveal the mechanism of population differentiation in sponge gourd, and also form the basis of following target QTL cloning, and contribute to eliminating the difference of daily flowering time between L.acutangula Roxb. and L.cylindrica Roem. and the application of interspecific hybrid advantage in sponge gourd.

有棱丝瓜和普通丝瓜的日开花时间相差近12小时，花期隔离阻碍了二者间的基因流动，促进了种群分化。为了探明这一机制的遗传基础，我们的前期工作对丝瓜的转录组进行了测序，通过序列分析成功开发了8523对EST-SSR标记；同时将有棱丝瓜S304和普通丝瓜P93075杂交，培育了一个F2遗传群体，利用新开发的分子标记，构建了一张包含170个标记的遗传图谱，并对丝瓜日开花时间性状进行了QTL初步定位。本项目拟在此基础上，选择主效QTL作为研究目标，通过回交、自交培育目标QTL区段的近等基因系，作为精细定位群体；同时构建丝瓜基因组BAC文库，筛选包含目标区段的BAC克隆，对其测序开发分子标记，利用这些标记和精细定位群体，对目标QTL进行精细定位。通过本项目的实施，一方面有助于从进化上揭示普通丝瓜和有棱丝瓜的种群分化机制；另一方面能够为下一步克隆目标QTL、打破种间花期隔离、利用丝瓜种间杂种优势打下基础。

植物开花时间近年节律（开花期）的研究已经十分深入，而近日节律（每天开花的时间）的相关研究较少。有棱丝瓜和普通丝瓜的每日开花时间相差近12小时，为研究植物开花近日节律提供了良好的实验材料。在本项目的资助下，我们在国际上率先完成了丝瓜转录组测序、EST-SSR 分子标记的开发、EST-SSR 分子遗传图谱和SLAF 高密度遗传连锁图谱构建、丝瓜基因组BAC文库的建立、开花时间QTL 定位等工作；同时，从本课题组已构建的丝瓜种间染色体片段渐渗系（有棱丝瓜S304 作轮回亲本，普通丝瓜P93075 作供体亲本）中，利用分子标记结合表型选择，筛选到包含普通丝瓜开花时间主效QTL 位点QFT1 渗入片段的株系，该株系开花时间比有棱丝瓜S304 晚4 个小时左右，命名为NIL-QFT1，将控制丝瓜开花时间性状的多个QTL 位点分解成为单个孟德尔因子；利用NIL-QFT1 构建精细定位群体，采用BSA-seq 测序结合经典图位克隆方法将丝瓜每日开花时间主效QTL 位点QFT1 定位于1 号连锁群0.32 cM 范围内。通过本项目的实施，一方面极大的推动了丝瓜基础研究的进展，另一方面能够为下一步克隆丝瓜每日开花时间相关基因、打破丝瓜种间花期隔离、利用种间杂种优势奠定基础。