‘峨眉问春’冬季短休眠性状的分子基础及遗传定位研究

The length of winter dormancy lasting in tea plant (Camellia sinensis) is an adaptive critical and economically important trait. ‘Emei Wenchun’ (EW) is a new clonal tea clone with a short period of winter dormancy (at least 60 days shorter than ‘Fuding Dabaicha’). However, very little is known about the molecular and genetic characteristics of that trait. Previously, we have observed that ‘endodormancy’ was almost absent in EW during winter. We also constructed a segregation population consist of over 1000 offspring of EW and a SSR-based genetic map for tea . In this project, we will investigate the internal mechanism of the short winter dormancy trait of EW from the phenotypic, physiological and molecular levels. More importantly, we will genotype the EW segregation population (>600 individuals) with about 120 SSR markers distributed in the whole tea genome and 30 candidate gene markers. Phenotype data include the timing of bud set, bud flush and year increment will be collected from the segregation population. Then, QTL mapping and QTL-candidate gene co-location analyses will be performed to identify the breeding-prefered alleles. By the way, we will screen the individuals with a common father from the maternal half-sib population using SSR markers. The results of this project will enrich our understanding of winter dormancy trait of C. sinensis and will facility the breeding of early-sprouting tea cultivars.

茶树冬季休眠期长短对于其环境适应能力和栽培价值有重要影响。‘峨眉问春’（简称EW）是2014年四川审定的特早生茶树新品种，其冬季休眠期比常用对照‘福鼎大白茶’短60天以上，但相关分子基础及其遗传特点尚不清楚。前期工作中，我们证实EW冬季几乎不经历生理休眠，培育了EW子代大型分离群体，并完成了茶树SSR标记遗传图谱构建。本项目将从表型、生理和基因表达等方面深入比较EW和其它中晚生茶树品种的差异，解析其短休眠性状的分子基础；并对超过600份子代的分离群体进行表型观测和标记基因型分析（约120个覆盖茶树全基因组的SSR和30个候选基因标记），研究EW短休眠性状的遗传特点，进行QTL定位、候选基因-QTL共定位分析，发掘EW中有育种价值的基因位点。本项目还将利用SSR标记从EW半同胞系中筛选出有共同父本的全同胞群体。研究结果将丰富对茶树冬季休眠性状的认识，提高早生型茶树品种的育种和改良能力。

项目主要围绕茶树品种‘峨眉问春’（EW）的短休眠性状展开，探究其分子基础及其遗传特点。一方面从萌发表型、激素生理指标和基因表达等方面进行分析，发现EW越冬芽在修剪刺激下可以快速恢复生长，其成熟母叶中GA3和IAA水平总体高于对照，H2O2含量及ABA/GA3的比值低于对照；基因表达上EW越冬芽和生长芽近似程度显著高于对照。另一方面，对EW自然杂交子代进行表型观测和基因型分析，研究EW短休眠性状的遗传特点，成功为78.6%的子代找到了父本，其中有11株来自EW自交；利用EW×CM全同胞群体构建了高密度遗传图谱，包含4244个标记，平均间距为0.34 cM；发芽期观测结果表明EW子代大部分发芽比早生品种‘福鼎大白茶’更早，但只有少数（1%）能比EW更早；QTL定位结果发现5个稳定的QTL位点，分布在Chr3、4、5、9和14连锁群上，结合参考基因组和基因表达分析筛选得到22个QTL候选基因。研究结果丰富了对茶树冬季休眠性状遗传调控的了解，提高了早生型茶树品种的育种和改良能力。

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