大豆重组自交系群体NJRSXG百粒重超亲分离的遗传解析

The Genetic Constitution of Transgressive Segregation of the 100-Seed Weight in A Recombinant Inbred Line Population NJRSXG of Soybean

【目的】解析大豆重组自交系中百粒重的QTL及其等位变异效应,探究重组自交系中百粒重存在超亲分离的原因,为进一步培育不同类型百粒重大豆提供遗传依据。【方法】利用以先进2号和赶泰2-2为亲本衍生的重组自交系群体NJRSXG为材料,在2009—2011年共5种环境下测定百粒重表型数据,建立具有400个SSR标记的遗传图谱,选用QTLNetwork V2.1软件中混合模型区间作图方法(mixed model based composite interval mapping,MCIM)对表型数据和基因型数据进行大豆百粒重QTL定位研究。在定位结果基础上,分析每个重组自交系群体中每个家系百粒重QTL等位变异类型,建立百粒重QTL-allele矩阵。【结果】5种环境试验的平均结果,亲本先进2号和赶泰2-2的百粒重分别为16.92和14.14g,重组自交系百粒重变幅为12.09—25.01 g,存在超亲分离,多环境下遗传变异系数(genotypic coefficient of variation,GCV)为16.06%,遗传率为96.17%。利用MCIM方法联合5环境原始数据,总共检测到10个加性QTL和9对上位性QTL,10个加性QTL的表型变异解释率变幅为0.69%—14.93%,其中Sw-05-2、Sw-08-1、Sw-12-1和Sw-17-1的表型变异解释率较高,分别为6.91%、14.93%、7.80%和5.01%,Sw-13-3为以往未见报道并兼具加性和上位性效应的位点。上位性QTL的表型变异解释率较小,变幅为0.31%—3.44%,其中Sw-e4的表型变异解释率最高。联合多环境方差分析和QTL定位结果,解析大豆百粒重的遗传结构,发现加性QTL累积贡献了47.91%表型变异,上位性QTL累积贡献13.06%表型变异,未检测出的微效QTL累计解释了35.20%的表型变异。在定位的同时,获得了QTL等位变异的效应,分析重组自交系及其亲本中百粒重QTL等位变异的组成,建立了NJRSXG的百粒重QTL-allele矩阵;两亲本分别具有7对和3对加性增效等位变异,属互补型组合;矩阵中没有一个重组自交家系包含所有减效等位变异或增效等位变异,表明重组自交家系具有进一步改良的潜力;大粒型家系具有较多增效等位变异,小粒型家系具有较多减效等位变异;说明百粒重位点间的重组是产生超亲家系的重要原因。【结论】利用重组自交系群体能够产生超亲分离家系;联合多环境数据检测到10个加性QTL和9对上位性QTL;百粒重QTL位点间的重组是超亲分离的原因;重组自交家系间具有进一步重组的潜力。

【Objective】 The present study aimed at exploring the QTL and their allele effects of the 100-seed weight in a recombinant inbred line（RIL） population for revealing the genetic mechanism of transgressive segregation,and providing guidance for breeding for different seed size types in soybeans. 【Method】 The RIL（recombinant inbred line） population NJRSXG derived from a cross between Xinjin 2 and Gantai 2-2 was tested and measured for their 100-seed weight in five environments from 2009 to 2011. The genetic map with 400 SSR markers was established for QTL mapping using the mixed model based composite interval mapping（MCIM） method in QTL Network V2.1 software. Based on the QTL mapping,the QTL-allele constitutions of each line of the RIL population was obtained,and the corresponding QTL-allele matrix was established. 【Result】 The 100-seed weight of the parents,Xinjin 2 and Gantai 2-2,were 16.92 g and 14.14 g,respectively,with those of the RILs ranging from 12.09 g to 25.01 g,showing an obvious transgressive segregation. The genotypic coefficient of variation（GCV） was 16.06%,and the overall heritability was 96.17% from a joint dataset analysis. Ten additive QTL and nine epistatic QTL pairs were detected in the joint dataset using an MCIM method. The phenotypic variation explained by additive QTL was ranged from 0.69% to 14.93%,and the four major QTLs,i.e.,Sw-05-2,Sw-08-1,Sw-12-1 and Sw-17-1,were 6.91%,14.93%,7.80%,and 5.01%. The Sw-13-3 with both additive effect and epistasis effects had not been reported before. The phenotypic variance of epistatic QTL pairs was small,and ranged from 0.31% to 3.44%. The genetic components of 100-seed weight was estimated from the mapping results,and the analysis of variance for the joint dataset,the genetic contribution due to additive QTL,epistatic QTL pairs,and collective unmapped minor QTL were 47.91%,13.06%,and 35.19% of the phenotypic variation,respectively. From the mapping procedure,the allele effects of all the loci were also obtained,and the genetic constitution of the QTL-alleles for each line of the RIL population and its parents was used to establish the QTL-allele matrix. The two parents have seven and three loci with positive additive effects respectively; therefore,this is a complementary pair of parents. No lines of the RIL population had all positive alleles or all negative alleles,indicating a hidden potential of recombination,and the lines with larger seed weight had more positive alleles,while the lines with smaller seed weight had more negative alleles,which implies that recombination among loci was the major cause for transgressive segregation of the 100-seed weight in the RIL population. In addition,it was also found that there was still a possibility to improve the 100-seed weight through further recombination. 【Conclusion】 The transgressive segregation of 100-seed weight can be found in a RIL population; 10 additive QTL and 9 epistatic QTL were detected using the joint dataset tested under five environments. The transgressive segregation was caused by recombination among loci between parents,and the potential for further improvement through recombination among RILs still exists.