Laboratory of Cellular and Molecular Cytogenetics, Department of Botany, University of Delhi, 110007, Delhi, India.
Theor Appl Genet. 1996 Apr;92(5):566-71. doi: 10.1007/BF00224559.
For the transfer of genes from B. tournefortii (TT) to the allotetraploid oilseed brassicas, B. juncea AABB, B. carinata BBCC and B. napus AACC, B. tournefortii was first crossed with the three basic diploid species, B. campestris (AA), B. nigra (BE) and B. oleracea (CC), to produce the allodiploids TA, TB and TC. These were tetraploidized by colchicine treatment to produce the allotetraploids TTAA, TTBB and TTCC, which were further crossed with B. juncea and B. napus to produce three-genome hybrids with substitution-type genomic configurations: TACC, TBAA and TCAA. These hybrids along with another hybrid TCBB produced earlier, the three allodiploids, their allotetraploids and the four diploid parent species were studied for their male meiotic behaviour. The diploid parent and the allotetraploids (TTAA, TTBB and TTCC) showed regular meiosis although the pollen viability was generally low in the allotetraploids. In the allodiploids (TA, TB and TC) only some end-to-end associations were observed without any clearly discernible chiasmata or exchange points. Chromosomes involved in end-to-end associations were randomly distributed at the metaphase/anaphase-I stages. In contrast, the three-genome hybrids (TACC, TBAA, TCAA and TCBB) showed normal bivalents whose number exceeded the expected bivalent values. Bivalents arising out of homoeologous pairing were indistinguishable from normal pairs by their disjunction pattern but could be distinguished on the basis of the heteromorphy of the homoeologous chromosomes. The three-genome hybrids could be backcrossed to allotetraploid oilseed brassicas as they had some fertility. In contrast, the allodiploids could neither be selfed nor back-crossed. On the basis of their meiotic stability, in terms of more pronounced homoeologous pairing and fertility for backcrossing, the three-genome configurations provide the best possible situation for the introgression of alien genes from the secondary gene pool to the allotetraploid oilseed crops B. juncea, B. napus and B. carinata.
为了将基因从 B. tournefortii（TT）转移到异源四倍体油料芥菜、B. juncea AABB、B. carinata BBCC 和 B. napus AACC，首先将 B. tournefortii 与三种基本的二倍体物种 B. campestris（AA）、B. nigra（BE）和 B. oleracea（CC）杂交，产生异源二倍体 TA、TB 和 TC。用秋水仙碱处理将这些异源二倍体加倍为异源四倍体 TTAA、TTBB 和 TTCC，然后与 B. juncea 和 B. napus 进一步杂交，产生具有替代型基因组构型的三基因组杂种：TACC、TBAA 和 TCAA。这些杂种以及更早产生的另一个杂种 TCBB，与三个异源二倍体、它们的异源四倍体和四个二倍体亲本物种一起，研究了它们的雄性减数分裂行为。二倍体亲本和异源四倍体（TTAA、TTBB 和 TTCC）表现出正常的减数分裂，尽管异源四倍体的花粉活力普遍较低。在异源二倍体（TA、TB 和 TC）中，仅观察到一些端到端的关联，没有任何明显可辨别的交叉或交换点。参与端到端关联的染色体在中期/后期-I 阶段随机分布。相比之下，三基因组杂种（TACC、TBAA、TCAA 和 TCBB）表现出正常的二价体，其数量超过预期的二价体值。同源配对产生的二价体在分离模式上与正常二价体无法区分，但可以根据同源染色体的异型性来区分。三基因组杂种可以回交到异源四倍体油料芥菜中，因为它们具有一定的育性。相比之下，异源二倍体既不能自交也不能回交。基于减数分裂的稳定性，同源配对更明显，回交的育性更高，三基因组构型为从次生基因库向异源四倍体油料作物 B. juncea、B. napus 和 B. carinata 导入外源基因提供了最佳的情况。
