联合连锁与关联分析方法精细定位玉米穗行数主效QTL

Corn yield is a complex trait and mainly composed of ear number, kernel number (KN) and kernel weight. Also, KN could be decomposed into kernel row number (KRN) and kernel number per row. However, KRN is a quantitative trait and major genes for it have not been identified yet. Meanwhile, jointed linkage and association mapping has become an important means for isolation of genes controlling such complex quantitative traits. In our previous study, one major QTL for KRN, qkrn7, had been detected on chromosome 7 with a F2:3 population derived from a cross of Dan340 and Ye478 across seven environments. In this study, the candidate gene for qkrn7 and its favorite haplotype from Dan340 inbred line will be isolated using a jointed linkage and association mapping. Meanwhile, the distribution of favorite haplotype for qkrn7 will be analyzed with Dan340 and its derivatives. In addition, effect of the candidate gene for increasing kernel row number will be detected with single fragment introgression lines under multiple genetic backgrounds. In summary, these results will play an important role in molecular breeding for high yield in maize.

玉米产量构成因子包括穗数、穗粒数和粒重，其中穗粒数可分解为穗行数和行粒数。穗行数属于数量性状，目前尚未有相关基因被克隆。同时，联合连锁与关联定位已成为解析复杂数量性状的重要手段。通过以自交系丹340和掖478组配的F2:3定位群体，联合7个环境表型，鉴定出第7染色体上存在稳定表达的控制玉米穂行数的主效QTL qkrn7。在此研究基础上，本项目以自交系丹340和掖478组配的BC3F2连锁定位群体，284份自交系构成的关联分析自然群体为材料，通过联合连锁与关联分析，挖掘和鉴定丹340自交系中能够增加穗行数的主效位点候选基因和优异单体型。同时，基于自交系系谱，解析来自丹340的穗行数增效位点qkrn7的优异单体型在其衍生系中的传递与分布；另外，利用多个遗传背景下目标区段的单片段回交导入系，分析该候选基因在不同遗传背景中增加穗行数的效应，为开发玉米高产分子育种工具提供理论与实践基础。

穗行数是玉米产量构成因子之一，其遗传基础的解析对认知产量性状形成的机理具有重要意义。本项目以203份温带玉米自交系为材料，利用其全基因组基因型数据和多个环境下穗行数表型数据，开展全基因玉米穗行数关联分析，3个环境下共检测到9个与穗行数显著关联（P < 0.0001）的SNP，分别位于玉米染色体框1.02、1.10、7.03、8.02、9.06 和10.03，获得4个候选基因。以含有来自于丹340第7染色体上控制穗行数主效位点的掖478染色体片段导入系材料W29-8与掖478杂交构建的BC3F3分离群体及其后代家系将KRN7定位于标记YD72-YD82（<1Mb）之间。进一步通过BC3F5、BC3F6分离群体重组单株的筛选及验证，将KRN7精细定位于标记YD72-YD93（<600 kb）之间。结合BSR分析和生物信息学信息，GRMZM2G048131和GRMZM2G132032可能为KRN7的候选基因，验证工作正在进行中。