小麦旗叶宽主效QTL-QFlw-5B精细定位及其遗传效应分析

During the later period of wheat growth, flag leaf (FL) maintains the highest photosynthetic efficiency among the green leaves, which play key roles in grain development and yield formation. It is of great value to unravel the genetic basis of FL for genetic improvement of plant type. Characterization the genetic relationships between FL and yield will facilitate molecular breeding programs designed to increase yield and nutrition use efficiency. QFlw-5B, a major stable QTL for FL width (FLW), was identified in a recombinant inbred line (RIL) population derived from the cross between Kenong 9204 (KN9204) and Jing 411 (J411) (KJ-RIL). This QTL could be reproducibly identified in 7 of the 8 environments, accounting for 6.6–19.8% of the FLW and FL area (FLA) variation with alleles from KN9204 increasing FLW by 0.04–0.07cm and FLA by 0.70–1.34cm2. The secondary mapping population as well as near-isogenic lines (NILs) of QFlw-5B has been developed. On the basis of previous study, this project aims to fine map QFlw-5B and characterize its effect on yield. The accurate genetic map of the target region will be constructed using the Affymetrixwheat 660K SNP array and bulked segregant RNA-Seq (BSR-seq). Novel molecular markers tightly linked with the target gene will be developed based on bioinformatics and comparative genomics. FLW, FLA and yield related traits will be phenotyped in in multiple environments. Combining molecular marker scores and phenotypic values, recombinants of the target region will be identified, thus achieving the goal of fine mapping of QFlw-5B.

旗叶是小麦生长后期光合效率最高的叶片，在籽粒和产量形成中起着重要的作用。解析小麦旗叶形态性状的遗传基础，探究其与产量性状的关系，对小麦株型遗传改良及高产高效型品种选育具有重要意义。利用科农9204×京411构建的重组自交系群体检测到控制旗叶宽的主效QTL-QFlw-5B，在7/8个环境被检测到，能够解释6.6–19.8%的旗叶宽、旗叶面积表型变异，来自科农9204的等位基因增加旗叶宽0.04–0.07cm，增加旗叶面积0.70–1.34cm2。本项目拟在前期工作的基础上，利用已经创建的次级作图群体和近等基因系，结合Affymetrixwheat 660K SNP芯片技术、生物信息学和比较基因组学分析方法，开发新的分子标记，构建靶区间饱和遗传连锁图谱。利用次级作图群体进行田间实验，对旗叶性状进行表型鉴定，结合靶区间高密度遗传图谱及分子数据，筛选重组体，实现QFlw-5B靶区间精细作图。

本项目基于前期科农9204×京411重组自交系群体8个环境下对旗叶宽初级QTL定位基础上，开展了对靶区段精细定位的研究，并利用次级作图群体对靶区段旗叶宽进行精细定位。利用KJ-RIL群体中筛选到KJ044、KJ319和KJ006共3个剩余杂合体构建次级作图群体，把靶区间缩小到720KM的物理区间，参考科农9204基因组注释，候选区间共有10个候选基因，包含61个SNP/InDel。其中差异表达的有2个基因。遗传效应分析表明，qFlw-5B优异单倍型可以同时提高籽粒宽、籽粒厚、千粒重，株高和单株产量，具有增产潜力。本研究结果为旗叶宽图位克隆奠定基础，为小麦分子育种提供理论指导。