猪7 号染色体上影响料肉比主效QTL 的分子遗传机理解析

Feed conversion ratio (FCR) directly determines the economic efficiency of the pig producer, and therefore it is a very important economic trait. Due to the high cost to measure FCR, its genetic architecture is still obscure so far. The applicants of this project have been located a quantitative trait locus (QTL) of FCR on chromosome 7 both by a genome-wide QTL mapping and a genome-wide association anlysis (GWAS) in a White Duroc × Erhualian F2 resource population, and its effect is largest among the currently reported QTL. Based on the above mentioned reseaches, this project aims to fine mapping the QTL by linkage disequilibrium and linkage analysis, breakpoint recombination analysis and identical by descent analysis. In addition, the QTL genotypes of F1 boars will be inferred by marker-assisted regression analysis, and three F1 boars, of which QTL genotypes are QQ, Qq and qq respctively, will be selected to sequence the target region in order to gain all polymorphic loci in the tregion. The polymorphic loci, of which genotypes are coincident with the QTL genotypes, will be customized onto a DNA chip. The chip is used to genotype the F2 and outbreed populations, and the polymorphic loci, which are strong associated with FCR in all populations, will be pick out. According to the locations of the strongly associated loci, the target gene can be anchored, and its functions will be verified. This project will partially uncover the molecular genetic mechanism of FCR, and also pave a way for gene breeding of FCR in pigs.

料肉比的高低直接影响猪生产者的经济效益,因此降低料肉比具有十分重要的意义。由于受测定成本的限制，目前对料肉比分子遗传机理的研究还不是很深入。本项目组利用自建的白色杜洛克和二花脸杂交产生的F2资源群体，通过QTL定位和GWAS分析，在猪7号染色体上均检测到一个影响料肉比的QTL。该QTL是目前已报到的料肉比QTL中效应最大的一个。本项目在上述研究的基础上，拟通过连锁不平衡和连锁分析、断点重组分析和IBD分析，对该QTL进行精细定位。然后通过标记辅助分离分析,推测F1公猪的QTL基因型，并对QTL基因型分别为QQ、Qq和qq的个体各一个进行目标区域捕获测序，获取该区域内的多态位点。选取与QTL基因型吻合的多态位点，定制成DNA芯片，对F2和远缘群体进行检验，筛选出强关联的多态位点。根据强关联位点的位置，锚定目的基因，并对其进行功能验证，初步揭示料肉比的分子遗传机理，为它的遗传改良奠定分子基础。

料肉比直接影响猪生产者的经济效益。本项目组前期QTL 定位的基础上，对7号染色体影响料肉比的QTL进行遗传解析。首先在F2群体中，通过标记辅助分离分析，把QTL 精细定位到2.8763 Mb的范围内。然后通过基因填补，获取目标区域内所以多态位点，再进行GWAS分析。最强关联的SNP在34.846 Mb，与原来最强关联MARC0058766（34.80 Mb）的位置一致。在该区域内，HMGA1编码生长因子蛋白，是FCR的强候选基因。在已有的990杜洛克群体中进行GWAS分析，结果没有找到显著的关联区域。这说明用商业品种做基因定位需要很大的群体，因为主效位点通过高强度的人工选择后已经纯合或趋于纯合，而微效位点的定位需要很大的群体。由于已有的杜洛克群体中无法验证F2群体中的结果，因此需要组建了另外一个杂交群体，巴克夏与里岔黑猪杂交群体，即山下黑猪群体。在山下黑猪群体中，利用已经检测的182个GWAS分析结果，在7号染色体目标区域内检测到Top50的SNP，因此，有必要增加山下黑猪群体的大小，提高GWAS检测效率。