玉米穗粗主效QTL的克隆与功能分析

Utilization of improving ear diameter to increase the rows per ear is the effective way to increase the yield of single ear in maize，but up to now, the ear diamete gene cloning and the functional markers used in assited breeding were lacked. A set of SSSL population derived from two elite inbred lines in maize, lx9801 and Chang 7-2 were build early, and a loci for ear diameter in chromosome 3 was identified in a SSSL 10su055-1, and that loci located in the same region with the QTL qED3 we detected in a F2:3 population early. In this study, the BC6F1 back cross population derived from the SSSL line10su055-1 and recurrent parent lx9801 was used to clone the candidate gene for ear diameter, the candidate gene would be fine mapping and cloning through molecular marker developing, sister chromatid exchanging plant selection, trait identification, BAC library sequening, and funcitional analysis. This study can provide not only a theoretical evidence to clarify the molecular mechanism of ear diameter formation,but also useful gene resources for molecular crop breeding.

持续提高玉米产量的关键因素之一在于提高单穗产量，通过改良穗粗从而提高穗行数是提高单穗产量的有效途径，但迄今为止仍然缺少穗粗主效基因克隆的结果和可供用于分子标记辅助育种的功能标记。课题组前期建立一套玉米自交系lx9801背景的昌7-2单片段代换系，发现在第3染色体上的单片段代换系10su055-1 中存在一个控制玉米穗粗的主效QTL，且与课题组前期利用F2:3群体定位的玉米穗粗QTL（qED3）区间一致。本研究拟在前期研究基础上，利用含有目标性状基因的单片段代换系与lx9801回交构建BC6F1分离群体，通过分子标记开发，供体片段与受体目标基因片段交换单株的筛选，实现对目标基因的精细定位；然后通过对昌7-2 BAC文库的筛选与序列分析，确定控制目标性状的候选基因，并对其功能进行验证。该研究可以为明确玉米穗粗形成的分子机制提供理论依据，同时也为玉米新品种的选育和分子设计育种提供有用的基因资源。

穗粗是影响玉米产量的重要性状。本研究利用单片段代换系在前期对穗粗主效QTL初步定位在玉米第3染色体上工作基础上，成功构建了玉米穗粗主效QTL近等基因系BC5F1分离群体，利用21500株的分离群体，通过分子标记开发与交换单株筛选，将候选基因精细定位在3号染色体3.07bin上38Kb的物理距离内。通过生物信息学分析，在候选基因目标区段内预测有3个可能的功能基因，通过序列比对，确定1号基因为穗粗主效QTL候选基因，已经成功构建转化载体，分别对玉米和水稻进行了转化。该结果为穗粗主效QTL的功能验证和标记开发分子辅助育种提供了研究基础和出发基因，对其进行深入研究将有助于阐述穗粗形成过程中的分子机理。