玉米o16基因回交渗入o2系的分子标记辅助选择

在高赖氨酸玉米育种中，主要是以玉米opaque-2(o2)突变体作供体回交转育培育亲本材料，再行培育高赖氨酸杂交种。但是，迄今培育的o2玉米系及其杂交种的籽粒赖氨酸含量约为0.4%，不能满足食用和饲用的需求。为了提高o2玉米的赖氨酸含量，本研究利用一个新的高赖氨酸突变基因opaque-16(o16)的载体QCL3021作供体，o2玉米系太系19为受体，将o16基因回交渗入o2玉米系。在回交的每一世代及随后的自交世代，用o2基因内的SSR标记umc1066和o16基因的连锁SSR标记umc1141进行前景选择，再对中选单株进行全基因组SSR标记的背景选择，最后用染料结合赖氨酸法测定籽粒赖氨酸含量，以便保证筛选出遗传背景恢复率和赖氨酸含量均高的目标单株。在BC₂F₄代，获得携带o2和o16基因的家系17个，其遗传背景与o2玉米系相当(恢复率为92%~95%)，赖氨酸含量为0.469%~0.599%。其赖氨酸含量比普通玉米平均提高约122.63%；比高值亲本太系19(o2o2)平均提高约22.33%，增幅为6.11%~35.52%；比低值亲本QCL3021(o16o16)平均提高约65.86%，增幅为43.87%~83.74%。表明采用标记辅助选择技术将o16基因回交导入o2玉米，能有效提高玉米籽粒的赖氨酸含量，对高赖氨酸玉米的遗传改良和育种具有重要意义。

Molecular Marker-Assisted Selection for Corn o2 Introgression Lines with o16 Gene

The opaque-2 (o2) mutant is commonly used as a donor to breed high lysine corn. But the highest lysine content of the o2 line as well as the resultant hybrids is about 0.4%. So, it is necessary to increase lysine content for the staple food consumed by human and animals. QCL3021 line carrying opaque-16 (o16) gene is another high lysine mutant. This study was performed to transfer o16 gene into o2 line through hybridization between QCL3021 (donor) and o2 line Taixi 19 (receiver) followed by multiple backcrossing. The foreground selection was performed using simple sequence repeats (SSR) marker umc1066 for o2 gene and umc1141 for o16 gene in every backcrossing and subsequent inbred generation. Selected plants were then screened for recovery of genetic background using SSR markers covering the whole genome. Grain lysine content was determined by dye-binding lysine (DBL) method. Plants with high lysine content and higher genetic background recovery ratio were eventually chosen. In BC₂F₄ generation, 17 family lines which carry both o2 and o16 genes were identified, with the genetic background recovery ratio of 92%–95%, indicating that the genome of these lines was highly identical with o2 corn line. Lysine content of the selected plants was 0.469%–0.599%, which was an average increase of 122.63% fornormal corn,22.33% for the high parent line Taixi 19, and 65.86% for the low parent line QCL3021. This study demonstrated that molecular marker-assisted selection (MAS) for corn o2 introgression lines that were infiltrated with o16 gene was successful in improving grain lysine content. The established procedure can be applied in high lysine corn breeding and genetic improvement.