玉米骨干自交系京2416杂种优势及遗传重组解析

Heterosis and Genetic Recombination Dissection of Maize Key Inbred Line Jing2416

【目的】玉米骨干自交系京2416是以(京24×5237)×京24构建基础选系群体,利用高大严及同群优系聚合等选系技术选育的优良黄改群自交系。以其为父本育成的审定品种已有20多个,其中代表性品种京农科728,突破了黄淮海夏玉米籽粒机收技术瓶颈,成为中国首批通过国家审定的机收籽粒品种。通过分析京2416与X群种质的杂种优势,及其形成过程中的重组事件和黄早四基因组片段传递规律,解析京2416形成的遗传机制,以期为黄改系的进一步遗传改良提供参考。【方法】选用黄早四、京2416及其2个选系亲本(京24和5237)为材料,与5份X群代表性自交系根据NCII遗传设计组配杂交组合,利用F1产量相关性状单穗粒重的中亲优势、超高亲优势值和配合力效应值评估4份黄改系的杂种优势。对4份黄改系及5份X群自交系进行测序深度约为18×的全基因组重测序,用BWA、GATK等软件进行序列比对和变异检测,基于获得的SNP和InDel标记信息,利用GCTA和Treebest软件进行主成分分析和系统发生树构建,同源传递片段(identity-by-descent,IBD)使用IBDseq软件识别。【结果】通过比较分析黄早四、京2416、京24、5237与5份X群代表系所配杂交组合的F1产量相关性状发现,与其他3份材料(黄改系京24、5237和黄早四)相比,京2416具有更高的超高亲优势和一般配合力。基于全基因组重测序数据,分析重现了京2416形成过程中的重组事件,明确京2416的基因组组成,选系亲本京24和5237在京2416基因组中保留的比例分别为80.96%和19.04%。利用基因组测序数据解析从黄早四到京2416的IBD片段,结果表明,京2416从京24和5237 2个选系亲本中聚合了全部的9个重要黄改系特征性选择区域。【结论】骨干自交系京2416在遗传改良过程中,通过染色体重组聚合选系亲本京24和5237所有的9个重要黄改系特征性选择区域,从分子水平解释了京2416与X群代表系表现出更高配合力的遗传基础。

【Objective】Jing2416 is an elite maize Huangzaosi improved line(HIL), which was developed based on the basic population of(Jing24×5237) × Jing24 via employing multiple selection technologies, including high planting density, large population, strict selection and the pyramiding of elite lines from the same heterotic group. There are more than 20 registered varieties using Jing2416 as a male parent. Among them, the respective variety is Jingnongke728, which is one of the first varieties authorized by National Crop Variety Approval Committee in China and breaks through the technical bottleneck of huang-huai-hai summer maize mechanical grain harvesting. This study was to analyze the heterosis of Jing2416 crossed with the representative inbred lines from X group, and reveal the recombination events during the formation of Jing2416 and the identity-by-descent(IBD) segments transferred from Huangzaosi genome which can provide the genetic basis for the formation of Jing2416 and valuable guidance of the further genetic improvements of HILs. 【Method】Huangzaosi, Jing2416 and its two parents(Jing24 and 5237) were used as materials, and five representative lines from X group were used as tester lines, and their F1 hybridized combinations were obtained by NCII genetic mating design. We used the mid-parent heterosis, over-high parent heterosis and GCA(General combining ability) of kernel weight per ear to evaluate the heterosis of four HILs. The four HILs and five inbred lines from X group were sequenced with the average depth of 18×. We used BWA software to conduct the sequence alignments, and GATK software to identify the whole-genome variations. The PCA(principal component analysis) was calculated using GCTA software, and the phylogenetic tree was constructed using Treebest software. IBDseq software was used to analyze the IBD regions. 【Result】We found that Jing2416 had higher over-high parent heterosis and GCA than the other three HILs(Huangzaosi, Jing24 and 5237) to compare the yield related traits in the F1 hybridized combinations which were obtained by crossing Huangzaosi, Jing2416, Jing24 and 5237 with the five lines from X group. We identified the recombination events during the formation of Jing2416 and revealed the components of Jing2416 genome. We found that there were 80.96% and 19.04% of the genome regions of Jing2416 from Jing24 and 5237, respectively. We identified the IBD regions from Huangzaosi to Jing2416 and found that Jing2416 genome polymerized all nine important HILs characteristic selected regions from its two parents Jing24 and 5237.【Conclusion】The elite line Jing2416 genome polymerized all nine important HILs characteristic selected regions from its parents Jing24 and 5237 by the chromosome recombination during its genetic improvement. This study revealed the genetic basis for higher combining ability of Jing2416, which crossed with the representative lines from X group.