大豆低亚麻酸含量新位点qLLN-F的精细定位及候选基因分析

Linolenic acid is one of the polyunsaturated fatty acids in soybean oil which may benefit human health. However, linolenic acid is susceptible to the oxidation process during storage, which negatively affects the flavor and stability of the oil. Therefore, reducing the content of linolenic acid is very important for the improving of the quality and stability of soybean oil. In our previous study, we detected a new QTL, qLLN-F, for low linolenic content in a marker interval of 4.0 cM on linkage group F (chromosome 13) in soybean. This QTL explained 15.6% to 19.3% of the phenotype variance and was consistently detected in all the 7 environments in our experiments. Based on the information provided by our previous study, we plan to carry out this project: (1) to construct near isogenic line (NIL) segregating populations and develop enough amount of molecular markers in the target QTL region, and to finally fine map the new QTL, qLLN-F, (2) to search all the open read frames (ORFs) in the qLLN-F region and predict the candidate genes, and (3) to find the most possible candidate gene for qLLN-F by differential analysis of the DNA and cDNA sequence of the candidate genes in the parents. The results of this study may lay the foundation for the map-based cloning and functional complementary analysis of the QTL, and may also provide useful information for the breeding of low linolenic fatty acid soybean varieties.

大豆脂肪酸组分中亚麻酸是含有三个双键的不饱和脂肪酸，其在贮藏过程中容易被氧化而产生腥味，从而影响大豆油的风味和稳定性。因此，降低大豆油中亚麻酸组分的含量对于提高大豆油的品质和稳定性具有重要意义。前期研究发现，位于F连锁群（13号染色体）上一个与大豆低亚麻酸含量相关的新QTL（qLLN-F）在我们实验的所有7个环境中都被检测到，解释了15.6% - 19.3%的遗传变异，定位在大约4.0 cM的区间内。本项目拟在前期研究结果的基础上，通过构建目标QTL区域近等基因系分离群体，开发目标区域新标记，实现对qLLN-F的精细定位；同时利用生物信息学软件对精细定位区间进行基因预测，通过比较测序分析候选基因在亲本间核苷酸和转录水平的差异，确定最终的候选基因。研究结果可为进一步的大豆低亚麻酸含量主效QTL克隆和互补功能验证奠定基础，也可为大豆低亚麻酸品质育种提供理论依据。

大豆油中饱和脂肪酸和不饱和脂肪酸的含量及组成比例直接影响了大豆油的品质和用途。提高大豆油中油酸含量的同时，降低亚油酸和亚麻酸的含量，是提高大豆油品质和稳定性的有效方法，也是大豆品质育种的重要目标之一。本项目通过回交结合分子标记辅助选择的方法，针对前期定位的一个低亚麻酸位点qLLN-F区域进行近等基因系的构建，获得了BC5F1植株，并在标记区间开发了20对SSR引物；利用Thermo Fisher TRACE1310气相色谱仪，分别采用内标法和外标法，建立了快速、高效的大豆脂肪酸定量检测方法；以低亚麻酸材料FA10为共同父本分别与中豆32和中豆43杂交，构建了两个F2分离群体。采用区间作图法，在两个群体分别定位到39个和18个与脂肪酸组分相关的QTL，其中40个QTL与前人报道的QTL具有相同或相近的标记或标记区间，4对与亚麻酸含量相关的QTL既与前人定位结果一致，又在两个群体中被重复检测到；利用Illumina Infinium SoySNP50K BeadChip高密度SNP芯片对309份大豆早熟种质资源组成的自然群体进行基因型分析，结合多环境下的表型数据，对大豆蛋白质含量、脂肪含量、氨基酸含量、脂肪酸含量等品质性状进行了全基因组关联分析，共检测到87个相关位点，解释了8-89%的遗传变异。研究结果对于大豆品质性状，尤其是脂肪酸组分的遗传改良具有总要的理论价值。