油菜次生休眠特性与主要品质性状的关联性研究

Secondary dormancy is the main cause of underground seed bank’s long existence and volunteers’ multiplication in rapeseeds. Discovery of rapeseed varieties with low secondary dormancy is helpful to prohibit the occurrence of volunteers. And selection of varieties with high secondary dormancy is helpful to prohibit seed viviparity before harvest. Presently, combination of secondary dormancy and quality traits is taken as the priority direction in rapeseed breeding. Therefore, it is urgent and necessary to investigate the association between secondary dormancy and main quality traits (e.g. oil content, fatty acid content and glucosinolate content ) in rapeseeds. In the previous work, we screened out the varieties with high- or low- secondary dormancy, accompanying significant quality differences, from 89 rapeseed varieties that were collected at home and abroad. The varieties selected were used to create chromosome substitution lines with low- secondary dormancy background, and the candidate genes of secondary dormancy were identified. Basing on the previous work, this project aims to study the phenotypic differences and genetic relativity between secondary dormancy and quality traits in rapeseeds, and then reveal the relevance between secondary dormancy and main quality traits in rapeseeds, using methods of plant physiology, statistics and genomics. The results of this study would provide an important basis for the secondary dormancy breeding of rapeseeds with high qualities, and it would be meaningful in regulating the seed dormancy, preventing the volunteers and improving the quality of rapeseeds.

次生休眠是导致油菜地下种子库长期存在和自生苗繁衍的根本原因。发掘次生休眠弱的油菜品种，有利于防止自生苗；选择次生休眠强的品种，有利于防止收获前发芽。当前，将次生休眠育种与品质育种相结合已成为未来油菜育种的优先方向。因此，开展油菜种子的次生休眠特性与主要品质性状（包括含油量、脂肪酸组分、硫甙含量等）的关联性研究也愈发迫切和必要。在前期工作中，申请者从国内外89个油菜品种中筛选出品质性状差异显著的次生休眠特强、特弱品种，并以此回交构建了以弱休眠品种为背景的染色体代换系，遴选出次生休眠候选基因。本项目拟在前期工作基础上，利用生理学、统计学、基因组学等手段，探究油菜次生休眠特性与主要品质性状的表型差异及其遗传基础相关性，揭示油菜次生休眠特性与主要品质性状的关联性。研究结果将为我国优质油菜的次生休眠育种提供重要依据，同时对调控油菜种子休眠、控制自生苗危害、提高我国油菜生产品质等具有重要的现实意义。

次生休眠是指原来无休眠的种子由于不适宜环境条件的影响而诱发的休眠，是导致油菜产区地下种子库长期存在和油菜自生苗繁衍并造成危害的根本原因。当前，将次生休眠育种与品质育种相结合已成为未来油菜育种的优先方向。因此，开展油菜种子的次生休眠特性与主要品质性状的关联性研究具有重要的意义。本研究在前期工作的基础上，利用了项目组前期构建的染色体代换系群体中的178个株系，进行了油菜种子的次生休眠特性与主要品质性状（包括含油量、脂肪酸组分、硫甙含量等）的检测、表型数据统计及相关性分析、SNP遗传图谱的构建及QTL连锁分析。结果表明：两亲本各性状间差异及染色体代换系群体各性状在株系间差异均达到显著或极显著水平，且次生休眠率和6种脂肪酸含量、油分和硫甙含量均表现为连续分布，适合进行QTL检测。构建用于QTL定位的遗传图谱包含12339个多态性SNP标记，覆盖甘蓝型油菜基因组2031.982cM，平均图距0.667cM。利用此图谱，在2个环境共检测到位于7条染色体上的23个控制主要品质性状QTL位点，与棕榈酸、油酸、亚油酸、亚麻酸、芥酸和油分含量相关的QTL位点分别为4、6、3、4、3和3个，其中在A08和C03染色体上发现多种品质性状含量的QTL“富集区”。在A08染色体上检测到2个芥酸和油酸含量重叠的主效QTL，加性效应表现是相反的；在C03上检测到1个芥酸与油酸含量重叠的主效QTL，并且加性效应表现是相反的。在4个环境中，次生休眠率定位到1个QTL，解释表型变异10.5%-14.6%，其中主效QTL位点位于A09上，且加性效应为负值。