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.

讨论了利用多个供体系的基因进行基因组装，以获得高度基因重组系的最佳标记程序。所述程序分两步进行;在第一步中产生具有处于杂合状态的所有目标基因（根基因型）的植物，并且在第二步中，在根基因型的后代中选择具有处于纯合状态的所有基因的植物。当将基因杂交到特定受体品系的基因组上时，在供体之间杂交之前，应为每个供体单独进行回交。为了产生根基因型，通过回交获得的植物应按照植物结构和配置尽可能对称的时间表进行杂交。理想型的时间表在四到八个捐助者的存在。在没有任何特定受体基因组的情况下（不需要回交），供体本身应该在具有完全串联结构的时间表中杂交，其中具有较少靶标记的供体在早期阶段进入时间表。对于第二步中的选择，在所选植物之间组合使用单倍二倍化和杂交的策略将是高效的;选择从根基因型培育的单倍二倍化植物开始，并且在不存在具有目标标记基因型的植物的情况下，将具有最佳互补基因型的两个植物杂交以产生杂种，其继而被单倍二倍化用于下一轮选择。在该策略中，即使是具有多达20个靶标记的植物，也可以在约三轮选择中以几乎完美的确定性获得，每轮最多200个测试植物。

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.