小麦旗叶叶绿素含量的QTL定位及验证

QTL mapping and validation of chlorophyll content of flag leaves in wheat(Triticum aestivum L.)

旗叶是小麦主要的光合器官,叶绿素既是旗叶最主要的光合色素,也是品种选育中重要的表型指标,因此挖掘和利用旗叶叶绿素含量有关的主效基因/位点,对于培育高产稳产小麦新品种意义重大。以旗叶叶绿素含量差异较大双亲构建的双单倍体群体(DH群体)为材料,利用小麦90K SNP芯片对5个环境旗叶叶绿素含量进行QTL分析,共定位到20个旗叶叶绿素含量有关的遗传位点,表型贡献率为4.10%~27.16%;其中3个QTL(Qchl.saw-2D.1、Qchl.saw-4D.2和Qchl.saw-6A)能在多个环境条件下检测到;Qchl.saw-2D.1的遗传效应最高,该位点与2D染色体上已报道的其他叶绿素位点不同,初步确定是1个新的主效QTL。并进一步将Qchl.saw-2D.1紧密连锁的SNP标记开发为KASP标记,通过在含有共同亲本金麦919的RIL群体中验证其效应,发现在多个环境条件下具有Qchl.saw-2D.1有利等位基因的家系叶绿素含量显著或极显著高于其他家系。对Qchl.saw-2D.1、Qchl.saw-4D.2和Qchl.saw-6A所在功能区段进行基因注释,筛选到12个与叶绿素相关的候选基因,其中3个基因参与镁等金属离子的结合过程,5个基因参与调控叶绿体结构组成,4个基因参与调控光合作用过程中相关电子链的传递活性。本文研究结果为叶绿素调控的遗传机制提供了有价值的信息,并为高光效分子标记辅助育种提供依据与参考。

Flag leaf is the main photosynthetic organ in wheat.The chlorophyll content is not only the major photosynthetic pigment in flag leaf but also an important phenotypic indicator in crop breeding.Therefore,the identification of major loci/genes related to chlorophyll content in the flag leaf play an important role in breeding wheat varieties with higher grain yields and stability.In this study,we constructed a double haploid(DH)population from a cross of two cultivars with significant difference in chlorophyll content,and the chlorophyll contents of DH lines were detected under five environments.A total of 20 QTLs associated with chlorophyll content were detected using Wheat 90K single-nucleotide polymorphism(SNP)array,with contributions to phenotypic variation explained(PVE)from 4.10%to 27.16%.Three QTLs(Qchl.saw-2D.1,Qchl.saw-4D.2,and Qchl.saw-6A)were identified under multiple environmental conditions,in which Qchl.saw-2D.1 with the strongest genetic effect was different from previous studies and identified as a novel major QTL.Furthermore,Qchl.saw-2D.1was validated by a tightly linked kompetitive allele specific PCR(KASP)marker in a recombinant inbred line(RIL)population containing the co-parent Jinmai 919.Those lines with the favorable allele of Qchl.saw-2D.1 revealed significantly higher chlorophyll content than other lines under multiple environments.Moreover,a total of 12 candidate genes controlling chlorophyll content were identified in the three QTL regions.Based on gene annotation,three genes were involved in the binding process of metal iron,such as magnesium.Five genes were regulated the structural composition of chloroplasts,and four genes were engaged in the regulation of electron transfer activities during the photosynthetic process.In conclusion,this study will broaden the understanding of the genetic mechanism and provide a molecular basis for the marker-assisted breeding(MAS)of chlorophyll content in the flag leaf of wheat.