qFT-D3-2，一个棉花开花期相关QTL的精细定位与候选基因鉴定

Earliness is a major goal of cotton breeding. Flowering time is an important early-maturing trait and the research about genetic mapping of cotton flowering time related genes is a necessary way to improve the early-maturing cotton molecular breeding. In the previous study, a population of 137 recombinant inbred lines (RILs) was developed from a cross between early-maturing Gossypium. hirsutum. cv CCRI36 and late-maturing G. hirsutum. acc G2005 and a high-density genetic map was constructed by RAD sequencing technology. A QTL qFT-D3-2 related with flowering time was detected on D3 chromosome in four years, which indicated that there is a gene related with flowering time located on this target chromosome fragment. Therefore, this study will mainly focus on constructing the near-isogenic line (NIL) of target chromosome fragment to fine mapping and identify the candidate genes. And the candidate genes were detected by candidate gene correlation analysis using 355 upland cotton varieties with different maturity, and analyzing the genetic evolution of candidate genes. This research lays the foundation for analyzing the molecular mechanism of early-maturing trait of cotton and improving the molecular breeding of early maturity cotton.

早熟性是棉花品种培育的重要目标之一。开花期是棉花早熟性的重要标志，对棉花开花期相关基因的定位研究是进行早熟性状分子改良的必要途径。在前期研究中，本实验室利用陆地棉早熟品种中棉所36和晚熟品系G2005杂交构建了一个包含137个家系的重组自交系群体，通过RAD简化测序技术构建了一张高密度遗传图谱，在D3染色体上检测到了一个在4个年份中稳定表达的开花期QTL位点qFT-D3-2，说明该区段包含与棉花开花期相关的基因。因此本研究旨在根据目标区段构建近等基因系群体，对qFT-D3-2位点进行精细定位和候选基因鉴定；利用候选基因结合355份不同熟性陆地棉品种进行棉花熟性相关性状的关联分析，最终鉴定出目标候选基因，同时对候选基因进行遗传进化分析，为解析棉花早熟性状形成的分子机理和早熟棉花品种的分子改良奠定基础。

本项目基于一个BC1F2群体，对其开花期性状进行调查，得到了一个QTL位点qFT-D03，定位在D03_1348和zs156之间，LOD值为17.57，解释表型变异9.87%，说明该区段内确实存在控制开花时间的关键基因。通过对候选区段基因进行功能分析，结合转录组和qRT-PCR数据，在该区间内发现有一个与拟南芥组蛋白去乙酰化酶AtHDA6高度同源的基因Gh_D03G0986（GhHDA6），该基因在花器官和茎中高量表达。在拟南芥中过表达该基因，能够明显促进拟南芥开花提前。同时在棉花通过VIGS沉默该基因，沉默植株和空载对照相比，开花期推迟6天左右，株型和株高基本上没有差异。以上研究结果表明GhHDA6在棉花开花进程中起着重要的作用。本项目发表SCI论文1篇，在投SCI论文2篇；申请发明专利1项（已授权）。本项目确定了1个候选基因，并进行了其功能的初步探究，为棉花早熟分子育种提供了基因资源。