菊花不同生长时期耐寒性的遗传变异与动态QTL分析

Chrysanthemum is one of the ten famous traditional flowers in China and of the four leading cut-flowers in the world, thus possessing great ornamental and commercial values. Cold stress seriously affects chrysanthemum year-around production and its promotion and application in cold areas, and has become an important problem to be solved in chrysanthemum industry. Therefore, it is critically important to understand the genetic determination of cold tolerance and to breed new cultivars with improved cold tolerance for chrysanthemum. In this study, we are going to investigate the genetic variability of cold tolerance of chrysanthemum at four different developmental stages, i.e. seedling, vegetative growth, budding, and florescence stages in cultivar germplasm and hybrid progenies in two consecutive years. Then, we will construct high-density genetic linkage map and evaluate the population structure and linkage disequilibrium of chrysanthemums with different cold tolerance via SRAP (sequence-related amplified polymorphism), SSR (simple sequence repeat), and SNP (single nucleotide polymorphism) markers; and based on joint linkage-linkage disequilibrium mapping, we will identify the additive and epistatic QTL underlying cold tolerance of chrysanthemum at different stages by using conditional and unconditional dynamic QTL analysis, and achieve the consistent QTL expressing stable across different stages detected by both methods. Finally, we will predict the candidate genes related to cold tolerance based on the SNP information linked to QTL regions. The findings of this study will uncover the genetic basis and expression of dynamic QTL conditioning the cold tolerance in chrysanthemum.

菊花是我国十大传统名花和世界四大切花之一，观赏和经济价值高。低温胁迫严重影响菊花的周年生产供应和在寒冷地区的推广应用，已成为菊花产业中亟待解决的重要问题。明确菊花耐寒性的遗传基础，培育耐寒菊花新品种是解决该问题的关键。本项目拟连续两年调查菊花品种资源和杂交群体在幼苗期、营养生长期、现蕾期和盛花期等4个不同生长时期耐寒性的遗传变异；利用SRAP、SSR、SNP等分子标记构建菊花高密度遗传图，评价菊花品种资源的群体结构和连锁不平衡水平；基于连锁-连锁不平衡联合作图，通过动态QTL的条件与非条件分析探讨菊花不同生长时期耐寒性的加性与上位性QTL及其效应；综合连锁-连锁不平衡作图结果，获得“一致性”主效QTL；最后根据QTL区域的SNP标记信息预测耐寒性QTL关联的候选基因及其功能。研究结果将揭示菊花耐寒性遗传机制及耐寒性QTL的动态表达特性，对菊花耐寒性的遗传改良具有重要理论和实践指导意义。

低温胁迫严重影响菊花的周年生产供应和在寒冷地区的推广应用，已成为菊花产业中亟待解决的重要问题。明确菊花耐寒性的遗传基础，培育耐寒菊花新品种是解决该问题的关键。本研究调查了菊花F1群体和品种群体在不同生长时期的耐寒性（LT50）的遗传变异，并通过连锁作图和关联分析解析菊花耐寒性QTL的动态表达机制。结果表明，菊花F1群体舌状花和不同时期叶片耐寒性的变异系数为22.17%~46.14%，杂种优势和超亲分离现象普遍存在。混合遗传分析结果表明苗期和盛花期叶片的耐寒性由2对表现为加性-显性-上位性效应的主基因控制，主基因遗传率分别为88.56%和65.86%。QTL定位在各时期共检测到21个QTL与叶片耐寒性显著相关，单个QTL的贡献率为6.47%~68.89%。基于混合线性模型的关联分析和SSR、SRAP分子标记数据，在各生长时期检测许多等位变异位点（P < 0.01）与叶片耐寒性显著相关，但是未发现标记位点同时与两年各生长时期的叶片耐寒性显著相关；另外，在2016和2017年度分别检测到10个和58个显著等位变异，两年间相同的位点有3个；结合LT50表型数据和优异等位变异，筛选出优异耐寒品种资源。基于高质量SNP位点和混合线性模型的关联分析，共挖掘出24个与脚芽期、现蕾期、盛花期叶片耐寒性和盛花期舌状花耐寒性相关的SNP位点（P < 0.001），其中5个SNP位点的表型效应值小于– 4 ℃，为优异等位变异位点；通过显著性SNP位点所在的SLAF标签序列与菊花转录组数据库进行比对分析，筛选到5个候选基因，其中CL2042.Contig4_All 和Unigene40993_All可能与冷胁迫有一定关联。研究结果将揭示菊花耐寒性遗传机制及耐寒性QTL的动态表达特性，对菊花耐寒性的遗传改良具有重要理论和实践指导意义。另外，发表项目相关SCI论文5篇、核心期刊论文8篇；培养博士生1人、硕士生3人。