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。

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.