梅花绿萼性状的遗传分析与分子标记定位

Mei (Prunus mume Sieb. et Zucc.) is an unique early spring ornamental woody plant in China. As a typical cultivar, mei with green calyx is well liked by people due to green calyx and white petal just like snow. However, the variety is less and its breeding through traditional hybridizations is time consuming and inefficient. This issue can be addressed by marker-assisted selection derived from our profound understanding of the genetic control of green calyx. This project aims to illustrate a picture of the genetic architecture of green calyx by genetic mapping. Specific objectives are to: (1) construct a high-density genetic linkage map for a F1 progeny of 180 hybrids from a cross between sharply different cultivars, female P. mume 'Liu Ban' and male P. mume 'Huang Lve'. The map includes more than 3,000 SNPs, with an average map distance of < 1 cM, generated by using restriction-site associated with DNA-tag (RAD-tag) strategy, with these SNPs covering the entire genome of mei (8 chromosomes); (2) anchor the linkage map by more than 90% of mei assembled sequences through bioinformatics analysis; and (3) map specific qualitative trait loci (QTLs) underlying green calyx by powerful statistical models and detect their candidate genes. This study will pave a road for gaining new insight into the genetic control of green calyx and using this to design maker-assisted selection breeding and map-based gene cloning strategies for mei.

梅花是我国特有的早春观赏木本花卉，特别是绿萼型的梅花品种因其花萼绿色，花瓣洁白如雪，自古以来广受人们的喜爱。目前，绿萼型梅花品种较少，新品种培育以人工杂交为主，花费的时间长、效率低。因此，本项目通过构建遗传图谱来进行分子标记辅助育种并揭示绿萼性状形成的遗传机制，具体内容为：（1）以梅花品种‘六瓣’与‘黄绿萼’杂交得到的180株F1子代为试验材料，利用与限制性酶切位点相关DNA标签测序（RAD-tag）策略挖掘遗传作图群体中的SNP，构建含有3000个以上SNPs、标记平均间距小于1 cM的梅花高密度遗传连锁图谱，并覆盖梅花8条染色体。（2）利用生物信息学的方法，将90%以上的梅花参考基因组序列锚定在该遗传连锁图谱上。（3）利用质量性状定位模型分析影响绿萼性状的QTLs，并挖掘与其相关的候选基因。本研究结果旨在揭示绿萼性状形成的遗传机制，为今后开展分子标记辅助育种和基因图位克隆奠定重要基础。

梅花因其花期早、花型丰富、花色繁多和花香独特等特点被广泛应用于园林绿化，特别是绿萼型的梅花品种更受人们的喜爱。目前，培育绿萼型梅花品种多采用杂交育种的方式，花费时间较长。因此，本项目通过构建高密度遗传图谱定位绿萼性状的QTL，揭示绿萼性状形成的遗传机制，具体内容为：（1）以梅‘六瓣’和‘黄绿萼’杂交所构建的216株F1代杂种小苗为实验材料，利用RAD-tag测序策略，获得5012个SNPs标记，构建了梅花绿萼性状的高密度遗传图谱含有8条连锁群，总遗传图距为1807.14 cM，标记平均间距0.36 cM，锚定梅花基因组序列达92%。（2）构建梅花高维遗传干扰的基因组多点分析模式，估计多个标记区段之间的遗传干扰率。与母本相比，在父本基因组中存在广泛的遗传交换干扰现象。（3）构建复杂性状的QTL定位模型，通过对F1代开花情况的调查，定位影响绿萼性状的 QTLs为56个，挖掘到与其性状相关联的候选基因39个，主要是与MYB相关的转录因子LHY、D-乳酸脱氢酶和脂酰辅酶A合成酶相关的基因，为梅花绿萼性状的分子标记定向辅助育种奠定重要的理论基础，为今后揭示梅花重要观赏性状的遗传机制和基因组的进化具有重要意义。