高产广适大豆品种冀豆17产量QTL发掘和精细定位

Increasing yield is an important breeding goal of soybean improvement efforts. Breeding by design was considered as an efficient way for yield improvement. In order to understand the genetic mechanism of yield, it is necessary to identify quantitative trait loci (QTL) associated with yield. There were more than 150 yield QTL that had been reported in soybean, but there was little success in exploiting them in breeding program. Jidou 17 is an elite soybean variety in three ecological areas with highest yield in National multi-environment tests. In our research program, Jidou 17 has been employed as a common parent crossed with Suinong 14, Jidou 12 and Zhonghuang 13, respectively. Populations of recombinant inbred lines (RILs) have been obtained from these crosses and the RIL populations derived from these crosses have been genotyped using single nucleotide polymorphism (SNP) markers and high-density genetic linkage maps have been constructed. Based on the genetic linkage maps, a set of residual heterozygous lines (RHL) have also been developed. The rate of the average heterozygous loci among the RHLs was 4.2%, and the coverage of the heterozygous loci is about 93% of the whole soybean genome. In order to detect QTL associated with yield, a set of near isogenic lines (NILs) will be developed by maker assistant selection (MAS). The set of NILs will be evaluated across Northeast, Westeast and Huanghuaihai regions to detect the universal and specific yield QTL. As the genetic noise of other loci are limited in the NILs, the power of yield QTL mapping will be enhanced. In order to fine map the major seed yield QTL with large additive effect and get the closely linked markers, high generation sub-populations will be developed by MAS and used to find the key lines that recombined in the yield QTL region. The yields of the key lines will be evaluated, then linkage analysis will be performed to map the yield QTL in a precise position. In order to clarify their genetic contributions to yields plant height, number of nodes, number of branches, number of pods, seed weight will be investigated and correlation analyses between them and yield will be conducted. Finally, a conditional QTL analysis will be conducted to further assess the genetic contributions of these traits of agronomic importance to soybean yield. This research will not only provide information for understanding the genetic mechanism of yield, but also develop molecular markers for yield QTL for soybean breeding program by MAS.

发现影响大豆产量的关键基因，是解析大豆产量遗传网络、挖掘产量遗传潜力，从而提出突破产量水平的新育种方法的基础。课题组以国家区域试验平均亩产突破250公斤、三个生态区国家审定的大豆品种冀豆17分别与东北、西北、黄淮生态区主推品种绥农14、冀豆12、中黄13杂交培育出F6代重组自交系，并在全基因组SNP扫描、绘制高密度遗传图谱基础上，构建1套剩余杂合系，单个杂合系杂合位点比例平均为4.2%，全部杂合位点覆盖全基因组93%。本项目利用上述剩余杂合系培育近等基因系，消除基因组中其他基因干扰，提高QTL作图效率，在全基因组范围内高效发掘三个生态区间通用和特异的产量QTL；进一步培育主效QTL的高代次级分离群体，筛选得到QTL区间内的交换株系，精确鉴定交换株系产量及其构成性状，通过高精度连锁分析，精细定位主效QTL，通过条件QTL分析，解析产量构成性状对产量的贡献。为实现大豆产量突破奠定基础。

为了发掘冀豆17遗传背景中高产广适相关机制，本研究以冀豆17为共有亲本分别与冀豆12、中黄13和绥农14杂交构建的高世代重组自交系为材料，三个群体F6代分别含有199（冀豆17×冀豆12）、92（冀豆17×中黄13）和271（冀豆17×绥农14）个家系。利用简化基因组测序的方法获得各家系覆盖全基因组的SNP信息，并开发基于重组事件的bin标记，构建三张分别包含1970、929、2002个bin标记的高密度遗传连锁图谱，标记间平均遗传距离分别为1.28cM、2.85cM、1.25cM，三群体bin标记覆盖全基因组的92.7%。在石家庄（黄淮北片夏播生态区）、武威（西北春播生态区）、龙亢（黄淮南片夏播生态区）和绥化（东北春播生态区）四地三年连续鉴定三群体各家系的开花期、株高、主茎节数、分枝数、单株荚数、百粒重等生育期及产量相关性状。共检测到各性状相关的QTLs 151个，其中冀豆17×绥农14群体中位于第10号染色体Gm10:45004437-Gm10:48926334区间和第18号染色体Gm18:53534336-Gm18:57772396区间上的QTL，在石家庄、武威和龙亢环境均能稳定检测到，与株高、主茎节数、分枝数、单株粒数和百粒重均连锁，遗传贡献率最高，且增效基因均来自冀豆17。另两群体中多环境稳定检测到的QTLs主要富集于第6、第10和第19号染色体上。为进一步缩小QTL置信区间，将三个群体测序数据整合分析，共得到与共有亲本冀豆17间存在多态性的SNPs 15,535个，利用全基因组关联分析（GWAS）的方法对定位结果进行验证及候选区段分析。结果检测到性状相关的SNP位于第6号、第10号、第18号、第19号染色体上的QTLs置信区间内。进一步明确Chr06上16-44Mb区间内存在两个QTL，leadSNP分别为Gm06:19403905bp 和Gm06:43607625bp。绘制了QTL位点及性状之间的遗传网络关系，明确了各位点对产量构成性状的遗传贡献。提出冀豆17的高产和广适性主要与E2、E3、Dt1、Dt2等主效位点内冀豆17等位变异在不同环境下稳定作用相关。