基于LD作图的油茶不饱和脂肪酸含量变异位点研究

Camellia oleifera, as an important non-wood tree species for seed oil in China, has received more attentions owing to its higher unsaturated fatty acid contents benefited to human health. It is necessary to obtain the molecular markers, which is associated with oil quality during oil-tea breeding research based on oil-tea cultivars with large variation in oleic acid and linoleic acid content. On the basis of the association population, which is consisted by 250 individuals from the entire natural distribution region of Camellia oleifera, and the linkage population established by controlled crossing between four elite oil-tea parents, the study will focus on the discovery of the polymorphic SSR and SNPs loci within the Cvfad2 gene family, which code the key enzymes of polyunsaturated fatty acid content. Moreover, the haplotype (a block of linked ordered markers) frequencies of locus genotypes will be investigated using maximum-likelihood in the association population, and all the association tests between markers (haplotype) and traits will be conducted using the unified mixed-model method(MLM). Furthermore, the significant associations are being validated in the linkage population. In this study, the markers derived from Cvfad2 gene family will provide the informative single-marker or haplotype associated with the tea-oil quality, and further clarify the allelic effects on natural variation of oil quality in Camellia oleifera. In a word, the data will provide a theoretical foundation for the power of LD mapping to identify useful alleles within functional genes controlling phenotypic traits in Camellia oleifera.

油茶是我国重要木本油料树种，其种子油（74%~87%为油酸）是高档保健食用油。利用油酸、亚油酸含量差异显著的种质资源，筛选与茶油品质关联的分子标记对油茶育种具有重要意义。本研究基于前期构建的涵盖全分布区遗传资源的油茶群体（250个以上）及杂交F1代群体（300个以上），通过测序、毛细管电泳和Illumina基因分型法挖掘油茶油酸去饱和酶基因区域内（包括启动子、5' UTR、内含子、外显子、和3' UTR）SSR、SNP位点和基因分型；采用最大似然法分析单体型频率，统一混合模型法分析标记、单体型与表型性状的关联性；并进一步在F1代群体中验证，同时利用qRT-PCR法探析多态性位点是否调控基因的转录水平。通过研究，确定油茶基因组连锁不平衡（LD）延伸模式，获得油酸去饱和酶基因与油茶品质关联的标记位点或单体型，探明其对表型变异的基因效应，为LD作图用于油茶MAS育种的可行性和准确性提供科学依据。

油茶是我国重要木本油料树种，其种子油富含油酸（74%~87%），是高档保健食用油。利用油酸、亚油酸含量差异显著的种质资源，筛选与茶油品质关联的分子标记对油茶育种具有重要意义。.本研究以前期构建的油茶遗传群体为材料，分析了油脂品质相关性状的遗传规律；检测调控油脂品质的关键候选基因内的多态性位点；研究关联群体的群体结构和LD衰退距离；筛选了与表型性状相关的单一标记和单体型，计算相关标记对表型的贡献率，并在验证群体内验证。经过三年的研究和探索，获得如下研究结果：.（1）检测了含油率及茶油品质性状，表明各性状存在丰富变异，大致符合正态分布；性状间广泛存在显著相关性，尤其是C18:1和C18:2含量呈极显著负相关。.（2）筛选并克隆了4个控制茶油品质的关键候选基因，分析了4个候选基因的多态性位点。共检测到最小等位基因频率高于5%的多态性位点364个，包括2个Indel和362个SNP，平均分布密度为 1/19.8bp。.（3）解析了关联群体的群体结构，确定整个群体不符合HWE平衡，可分为4个符合HWE平衡的亚群，且亚群间存在较大遗传分化。油茶基因组内的LD在基因内就已衰退，候选基因内的LD作图是可行的。.（4）开展了标记或单倍型与性状间的关联分析，筛选出与表型性状关联的单个标记90个、单倍型1个，这些标记对关联表型性状变异的贡献率在17.93%~1.87%。分析了部分关联标记的基因作用模式，多以超显性模式为主，未检测到共显性基因作用模式。.（5）在验证群体中验证关联群体获得的标记-性状关联，将显著关联的标记-性状对减少至3对（Q<0.10），并明确了3个多态性位点的基因型。.本研究揭示了LD作图在油茶MAS育种中的准确性和可靠性，并探索了多态性关联标记对表型性状的调控模式，为油茶品质分子辅助育种的准确性和育种策略提供了科学依据。