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

Mutant opaque-2 (o2) is commonly used as a donor in high lysine corn (Zea mays L.). Currently, the highest lysine content of the o2 line or the resultant hybrid is only 0.4%, and it is necessary to breed corn lines with higher lysine content. This study aimed at transferring another high lysine gene, opaque-16 (o16), into o2 corn line. The o16 donor parent QCL3021 was crossed and backcrossed with Taixi 19 (o2 line) until the BC2F4 generation. In every backcrossing and subsequent inbred generation, o2 and o16 genes were selected using simple sequence repeat (SSR) markers umc1066 and umc1141, respectively. The backgrounds of selected plants were screened with 243 SSR markers spanning over the whole corn genome. Grain lysine content was determined using the dye-binding lysine (DBL) method. In the BC2F4 generation, 17 lines carrying both o2 and o16 were harvested, of which the genetic background recovery ratios were as high as 92-95%. This indicated that the genome of these lines was highly identical with the o2 line. Lysine contents of the selected plants ranged from 0.47% to 0.60%. The average lysine content of these plants was 125% higher than that of normal corn, 23% higher than the high parent Taixi 19, and 64% higher than the low parent QCL3021.

摘 要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22.33%, 增幅为6.11%∼35.52%; 比低值亲本QCL3021(o16o16)平均提高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。