控制玉米雄穗下多叶宽主效QTL-qLW5的精细定位与功能变异分析

The practice of breeding has shown that the increase of maize yield is due to the increase of maize high-density tolerance. As an important factor of leaf size, leaf width is an important indicator of maize high-density resistance. In the previous study, a leaf width QTL named by qLW5 was identified between bnlg118 and umc1680 on chromosome 5 by using the RIL and the permanent F2 population. qLW5 is a major QTL detected stably in RIL and IF2 populations with the phenotypic variation of leaf width in multiple leaf positions more than 10%. The effect of qLW5 is mainly additive with some dominant effect. In this research, we will use the introgression lines harbored qLW5 and the recurrent parents to develop the fine mapping population, screen the polymorphism markers and recombinants in the segregation population, combine the chromosomal displacement mapping method, bulk segregation analysis with high throughput sequencing methods and association analysis methods to identify the qLW5 functional variance, alleles and their effects, excellent alleles and their selection effects. The research results will play important role in cultivating new maize hybrids with narrow leaves and tolerant to high density and reveal the genetic mechanism of leaf width.

育种的实践证明玉米产量的增加是由于玉米耐密植能力的增加。叶宽作为叶片大小的重要构成因子是玉米耐密植的一个重要指标。在前期的研究中，我们利用RIL和永久F2群体在第5染色体标记bnlg118和标记umc1680之间发现一个叶宽的主效QTL命名为qLW5。qLW5在RIL和IF2群体中均可以稳定的检测到，在RIL群体中多个叶位的叶宽解释的表型变异均超过10%，是一个主效的QTL，效应值主要以加性效应为主，具有部分显性效应。本研究计划利用包含qLW5的导入系与轮回亲本构建的回交分离群体，开发多态性标记，筛选交换单株，构建跨叠系，利用染色体置换作图的方法精细定位qLW5，同时采用BSA-seq和关联分析方法，鉴定控制叶宽主效qLW5候选基因及其在自然群体中的功能位点、等位基因及其效应、优良等位基因及其选择效应。研究成果将对培育窄叶片、耐密植玉米新品种和揭示叶宽分子遗传机理具有重要意义。

叶宽是影响玉米株型的重要因子，尤其雄穗下连续多张叶宽，直接影响冠层及下部叶片对光能的利用，最终影响产量。项目前期利用RIL和IF2群体，定位到一个qLW5，控制雄穗下连续五张叶宽，解释的表型变异超过10%，是主效的叶宽QTL。利用近等基因系NILqlw5构建了精细定位群体，将qLW5剖分成qLW5a和qLW5b两个紧密连锁的QTL。结合连锁分析和关联分析将qLW5a和qLW5b定位到21kb和39kb的范围内，明确了Zm00001d017472（编码阳离子氨基酸转运蛋白9）为qLW5a的候选基因。qLW5a上游3197bp的显著关联SNP分成三种单体型，不同单体型间的雄穗下第一至第五叶宽均存在显著差异，HAP1各叶位叶宽最窄，HAP3各叶位叶宽最宽。明确了Zm00001d017398（OBE2）为qLW5b的候选基因，5’UTR区域的3个显著的SNP，横跨LINE反转座子区域，最显著的两个SNP分成3种单体型，其中HAP1和HAP2在第2、3和4叶位叶宽均存在显著差异。提出了qLW5a和qLW5b可能协同通过WUSCHEL-CLAVATA途径调控叶原基分生组织的活性调节叶宽变异的机制。