为了在回交一代既能较好地消除靶基因的遗传连锁累赘，又能在进行背景选择的基础上选择到轮回亲本遗传背景回复率较高的单株，本研究构建了单株数分别为1 416和1 627的SCBC1F1和HCBC1F1两个不同遗传背景的回交群体。结合玉米叶片DNA大量、快速提取法，使用5个与opaque2（o2）基因连锁并已定位的SSR标记，在SCBC1F1与HCBC1F1群体中，对o2基因单侧的连锁累赘进行SSR分析，并与Ribaut（2002）的计算机模拟结果进行比较，结果表明，本研究获得的结果优于相应的计算机模拟结果。并对分子标记辅助选择体系在玉米回交育种中应用的若干理论问题进行了讨论，认为在实际应用MAS程序中，不仅要重点考虑最终决选的单株数（Ni），而且还应该考虑到实际有足够后代的中选单株数（Nj）。另外，结合预期要消除连锁累赘的图距，制备足够大的BC1F1群体是十分必要的。
In order to get rid of the linkage drag of target gene and get more selected individuals with better genetic recovery, two backcrossing populations (SCBC1F1 and HCBC1F1 ) of maize were constructed with its size up to 1 416 and 1 627 individuals each. Five SSR markers which are localized in and linked closely to opaque2 (o2) gene (Fig.1) were employed to analyze linkage drag of o2 in SCBC1F1 and HCBC1F1 populations. Foreground and background selection were processed in the two populations by those five SSR markers (Fig.2－5). Compared with the computer simulation results proposed by Ribaut (Table 2), the MAS results were more exercisable and convictive. It suggests that, when the MAS program is put in practice of plant backcrossing breeding process, to make sure the size of the backcrossing F1 population is appropriate, not only the number of the selected individuals ultimately (Ni), but also the number of the selected individuals ultimately with enough seeds (Nj) need to be considered (Table 1). Moreover, the length of the linkage drag is also an important parameter to estimate the size of BC1F1 population.
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