Construction of the crossing and selection schemes for producing high-degree gene-pyramided lines of DNA markers that are closely linked with desirable trait genes.

讨论了通过组装来自多个供体系的基因来产生高度基因金字塔系的最佳标记程序。该程序分两步进行；第一步产生所有客观基因处于杂合状态（根基因型）的植株，第二步在根基因型的后代中选择所有客观基因处于纯合状态的植株。当将基因插入特定受体系的基因组时，应在供体杂交之前分别对每个供体进行回交。为了产生根基因型，通过回交获得的植株应按照结构和布置尽可能对称的时间表进行杂交。在4至8个捐助者在场的情况下，提出了理想的时间表。在没有任何特定受体基因组的情况下（不需要回交），供体本身应该按照完全串联结构的时间表进行杂交，其中目标标记较少的供体在早期阶段进入时间表。在第二步的选择中，单倍体二倍体化和被选植株间杂交相结合的策略将是高效的；选择从根基因型培养的单倍体二倍体植株开始，在没有目标标记基因型植株的情况下，将具有最佳互补基因型的两个植株杂交产生一个杂种，该杂种又被单倍体二倍体进行下一轮选择。在这种策略中，即使一个植物有多达20个目标标记，也可以在大约三轮选择中获得几乎完美的确定性，每轮最多200个被测试植物。

Optimum marker-based procedures for producing high-degree gene pyramided lines via assembling genes from multiple donor lines were discussed. The procedures proceed in two steps ; a plant that has all objective genes in a heterozygous state (root genotype) is produced in the first step, and in the second step, a plant that has all the genes in a homozygous state is selected in the progeny of the root genotype. When pyramiding genes onto the genome of a particular recipient line, backcross should be performed separately for each donor prior to the crossing between the donors. To produce the root genotype, plants obtained through the backcross should be crossed in a schedule with structure and disposition of the plants as symmetric as possible. Ideal-type schedules in the presence of four to eight donors are presented. In the absence of any particular recipient genome (no need of the backcross), the donors themselves should be crossed in a schedule with completely tandem structure in which donors with fewer target markers enter the schedule in earlier stages. For selection in the second step, a strategy with combined use of haplo-diploidization and crossing between selected plants will be highly efficient ; selection starts with haplo-diploidized plants raised from the root genotype, and in the absence of a plant with the objective marker genotype, two plants with the best complementary genotypes are crossed to produce a hybrid, which in turn is haplo-diploidized for the next round of selection. In this strategy, even a plant having as many as 20 target markers, can be obtained at an almost perfect certainty in about three rounds of selection with a maximum of 200 tested plants per round.