中文摘要：

【目的】解析白菜类作物开花时间的调控位点,定位白菜类作物开花时间相关的候选基因,为白菜类作物抽薹开花时间的遗传改良提供依据。【方法】以116份白菜类作物组成的自然群体作为研究材料,分别种植在温室与露地2个独立的环境中,进行开花时间调查。同时,提取试验材料的DNA样品进行深度为1.2x的重测序,对测序数据用Pooled Mapping法进行过滤、与参考基因组比对,获得全基因组高密度SNP集合。经过条件过滤后,对高质量的SNP集合进行生物信息分析,包括试验材料的群体结构分析和全基因组连锁不平衡分析。从高质量的SNP集合中,随机挑选出2 000个变异位点,用Phy ML软件以最大似然法对116份试验材料进行系统发育树分析。用全部的高质量SNP集合位点通过软件Haploview进行全基因组连锁不平衡分析。最后,将高质量的SNP集合与开花时间数据结合,通过TASSEL和GAPIT软件包以及R程序语言进行全基因组关联分析。根据强关联峰值信号点位置和连锁不平衡区间定位开花时间候选位点,再通过白菜与同源物种拟南芥的基因共线性关系以及基因功能注释分析来预测白菜类作物开花时间相关的候选基因。【结果】不同种植条件下、不同类型的白菜类作物在开花时间上存在广泛差异。试验材料在露地环境下的开花时间高峰期明显早于温室环境下的材料;试验材料在露地环境下的开花时间总体表现出偏正态分布,而在温室环境下,开花时间各个阶段呈现出较为均衡的分布。温室与露地环境下的开花时间呈显著正相关。通过生物信息学分析最终得到的高质量SNP位点共103万个。试验材料的群体结构分析表明在系统发育树上各亚群内部分布较为集中,不同亚群之间的分布与材料的地理起源密切相关。全基因组衰减平均LD为2.3 kb,表明在116份白菜类作物构建的群体内存在较为频?

英文摘要：

【Objective】To identify the genetic loci or candidate genes for flowering time regulation in Brassica rapa for improvement of pre-mature bolting resistance of B. rapa. 【Method】 In this study, 116 B. rapa germplasm accessions were selected to evaluate flowering time variations in greenhouse and open-field, respectively. Total genomic DNA was extracted with 1.2x re-sequenced depth. Filtering, mapping with reference by Pooled Mapping was conducted to obtain a genomic high quality SNP set. Then the population structure and linkage disequilibrium（LD） were analyzed using SNP set after condition filtering. In total 2000 SNP points were selected from all SNPs randomly to conduct phylogenetic tree analysis using Phy ML software with maximum likelihood method. All high quality SNPs were used to conduct genomic linkage disequilibrium analysis with Haploview software. Genome-wide association study（GWAS） for flowering time variations was then conducted based on software TASSEL, GAPIT and R. According to the position of strong association signals and LD block, the candidate signals for flowering time were identified. Eventually, flowering time candidate genes in B. rapa were predicted by gene colinearity relationship between A. thaliana and B. rapa, and gene function annotation.【Result】The 116 B. rapa accessions showed extensive variations in flowering time. Significant variation was also observed between greenhouse and open-field environments. The distribution of flowering time under open-field was partial normal, while the flowering time distributed evenly under greenhouse. Phenotypes of flowering time were significantly correlated between different environments, indicating that genetic effect played a crucial role in regulation of flowering time. A total of 1.03 million SNPs covering genome-wide were generated by biotechnology analysis. Population structure showed that accessions from each sub-group were clustered, and had a close relationship with geographic origin in phylogenetic tree. The linkage diseq