基于SNP遗传图谱对甘蓝型油菜部分脂肪酸 组成性状的QTL定位

目的 菜籽油在烹饪、食品加工及工业生产中广泛应用,因此,根据生产需要改善菜籽油脂肪酸组分是油菜育种的重要目标。通过对2种环境下甘蓝型油菜主要脂肪酸组成进行QTL定位分析,寻找甘蓝型油菜脂肪酸组分的QTL及影响本群体脂肪酸组分的候选基因。方法以人工合成甘蓝型油菜10D130和甘蓝型油菜常规品种中双11构建高世代重组自交系（RIL）为研究材料,分别于2016-2017年和2017-2018年2个年度在重庆市北碚区2个不同的环境中设置田间试验,收获自交种子,采用气相色谱法3次重复对种子的脂肪酸组分进行分析。利用油菜6K SNP芯片对该RIL群体进行基因分型,DNA样品预处理及芯片处理严格按照Illumina Inc 公司Infinium HD Assay Ultra操作说明进行。取最小阈值LOD 2.0利用JoinMap4.0软件构建高密度遗传连锁图谱。通过QTL IciMapping V4.1完备区间作图法对油菜主要脂肪酸组成进行QTL定位。结果 2种环境中,两亲本各性状间差异及RIL群体各性状在株系间差异均达到显著或极显著水平,且6种脂肪酸含量在2个环境中均表现为连续分布,适合进行QTL检测。构建用于QTL定位的遗传图谱包含1 897个多态性SNP标记,覆盖甘蓝型油菜基因组3 214.19 cM,平均图距1.69 cM。利用此图谱,在2个环境共检测到位于8条染色体上的23个控制脂肪酸组分QTL位点,与硬脂酸、油酸、亚油酸、亚麻酸、廿碳烯酸和芥酸含量相关的QTL位点分别为6、3、4、5、2和3个,其中在A05、A08和C03染色体上发现多种脂肪酸含量的QTL“富集区”。在A05染色体上检测到亚油酸和亚麻酸含量重叠的主效QTL,亚油酸与亚麻酸表现加性效应相同;在A08和C03上都检测到油酸、廿碳烯酸和芥酸含量重叠的主效QTL,油酸与廿碳烯酸及芥酸表现加性效应相反。与拟南芥脂肪酸代谢基因进行同源性比对分析,在17个QTL置信区间内筛选到22个候选基因,主要通过编码脂肪酸去饱和酶、全羧化酶合酶、碳链延长酶和参与酰基辅酶A生物合成等途径调控脂质的生物合成和代谢。结论 利用甘蓝型油菜6K SNP芯片准确定位了2种环境条件脂肪酸组成的QTL位点,筛选到位于A05、A08和C03染色体上多种脂肪酸QTL的“富集区”,并与拟南芥脂肪酸代谢基因比对出该群体油菜脂肪酸代谢基因,可作为改善油菜籽脂肪酸组成的重要区段及候选基因。

QTL Identification for Fatty Acid Content in Brassica napus Using the High Density SNP Genetic Map

【Objective】 Rapeseed oil is widely used in cooking, food processing and industrial production. Therefore, improving the fatty acid composition of rapeseed oil according to the specific production objective is an important goal of rapeseed breeding. In this study, QTL mapping of main fatty acid composition in Brassica napus under two environments was conducted, which was designed to search for the QTL and related candidate genes of fatty acid components in Brassica napus.【Method】 The high generation recombinant inbred lines (RILs) were used as experiment materials, which were derived from synthetic 10D130 and conventional variety Zhongshuang11, and field experiments were conducted in 2016-2017 and 2017-2018 with two different environments in Beibei District of Chongqing City, respectively. After self-pollinated seeds were harvested each year, fatty acid components of seeds were measured by GC with three technical repeats. Then, the RIL population genotype was analyzed with the rapeseed 6K SNP chip array. The DNA preparation and the chip preparation were processed strictly according to Infinium HD Assay Ultra manual of Illumina Inc. The SNP linkage map was constructed by using JoinMap 4.0 program with minimum LOD 2.0. QTL mapping of main fatty acid composition was conducted by composite interval mapping using software Windows QTL IciMapping V4.1.【Result】 In the two environments, the differences of parents’ traits and RILs population’s traits reached significant or extremely significant levels, and the contents of six fatty acids showed continuous distribution, which were suitable for the detection of QTLs. The reference SNP genetic map contains 1 897 polymorphic SNP markers, covering 3 214.19 cM of Brassica napus genome with an average map distance of 1.69 cM. Twenty-three QTLs loci of fatty acid components on 8 chromosomes were detected in two environments. The QTLs loci related to stearic acid, oleic acid, linoleic acid, linolenic acid, eicosapentaenoic acid and erucic acid contents were 6, 3, 4, 5, 2 and 3, respectively. And the “enrichment regions” of multiple fatty acid contents were found on chromosomes A05, A08 and C03. Meantime, the main QTL with overlapping linoleic acid and linolenic acid content was detected on A05 chromosome, showing the same additive effect. And the main effect QTLs, oleic acid with overlapping contents of eicosenic acid and erucic acid were detected on A08 and C03, which was opposite to the additive effect of eicosenic acid and erucic acid. Twenty-two candidate genes of fatty acid metabolic were found underlying confidence intervals of seventeen QTLs by comparing with homologous genes in Arabidopsis thaliana. These genes regulate lipid biosynthesis and metabolism through encoding fatty acid desaturase, total carboxylase synthase, carbon chain lengthening enzyme and participating in acyl coenzyme A biosynthesis. 【Conclusion】 The fatty acid composition QTL under two environments were mapped accurately with the 6K SNP chip of rapeseed, and the “enrichment regions” of multiple fatty acid QTLs on chromosomes A05, A08 and C03 were screened. Compared with Arabidopsis thaliana fatty acid metabolic genes, candidate genes for fatty acid metabolism in this population were detected, which could be used for improving fatty acid composition in rapeseed.