芸薹属异源六倍体的减数分裂行为及育性的遗传分析

Diploid-like meiotic behavior is fundamental for the formation and evolution of new allopolyploid species, but the genetic regulation and molecular mechanisms behind the cytological process are largely unknown. Although three cultivated Brassica allotetraploids originated from the pair-wise crosses between three Brassica diploids, the trigenomic allohexaploid species are not found in nature. We synthesized Brassica allohexaploids (2n=54, AABBCC) using three crossing strategies with the combinations of the genomes from the extant allotetraploids and diploids. They showed the diploidized and non-diploidized meiotic behaviors, and produced both the euploid and aneuploid progenies, suggesting that genome stability was B>A>C. In this project, by using multi-color FISH, the meiotic behaviors of three genomes in these allohexaploids and possible differences will be investigated, to reveal the cytological reasons for their differential instability. The genetic control for their meiotic irregularities and fertilities will be studied in the segregating populations from the crosses of the allohexaploids with different rates of seed-sets. The allohexaploids with improved fertility should be selected for breeding hexaploid Brassicas in future.

减数分裂行为的二倍体化是异源多倍体物种形成与进化的细胞学基础，然而其调控的遗传与分子机制有待研究。虽然芸薹属三个栽培二倍体种间的成对杂交进化出了三个栽培异源四倍体种，但自然界没有发现包含三个基因组的芸薹属异源六倍体种。我们前期通过芸薹属六个栽培种间的几种杂交途径合成的芸薹属三基因组异源六倍体（2n=54, AABBCC）均同时表现二倍化与非二倍化的减数分裂行为、产生整倍体与非整倍体后代，显示不同的基因组稳定性（B>A>C）。本项目拟采用多色FISH技术，研究异源六倍体的三个基因组在减数分裂中的行为及差异、揭示基因组不同稳定性的细胞学原因；利用不同育性的六倍体杂交产生的分离群体解析减数分裂异常程度及育性差异的遗传机制，为芸薹属异源六倍体的育种及遗传研究提供新材料与理论指导。