背景回顾：Many flowering plant taxa contain allopolyploids that share one or more genomes in common. In the Brassica genus, crop species Brassica juncea and Brassica carinata share the B genome, with 2n = AABB and 2n = BBCC genome complements, respectively. 

提出问题：Hybridization results in 2n = BBAC hybrids, but the fate of these hybrids over generations of self‐pollination has never been reported. 

主要研究：We produced and characterized B. juncea × B. carinata (2n = BBAC) interspecific hybrids over six generations of self‐pollination under selection for high fertility using a combination of genotyping, fertility phenotyping, and cytogenetics techniques. 

结果1-多代自交后杂交种育性趋于稳定：Meiotic pairing behaviour improved from 68% bivalents in the F1 to 98% in the S5/S6 generations, and initially low hybrid fertility also increased to parent species levels. 

结果2-杂交种核型：The S5/S6 hybrids contained an intact B genome (16 chromosomes) plus a new, stable A/C genome (18–20 chromosomes) resulting from recombination and restructuring of A and C‐genome chromosomes. 

结论：Our results provide the first experimental evidence that two genomes can come together to form a new, restructured genome in hybridization events between two allotetraploid species that share a common genome. This mechanism should be considered in interpreting phylogenies in taxa with multiple allopolyploid species.

许多有花植物类群都含有异源多倍体物种，包含一套或者多套相同的亚基因组。在十字花科芸苔属植物中，芥菜（Brassica juncea，2n = AABB）和埃塞俄比亚芥（Brassica carinata，2n =BBCC）共享B套基因组。这两个物种的杂交会形成杂种B. juncea × B. carinata（2n = BBAC），但是这些杂种在自交产生后代后的情况从未有过相关报道。本文中，作者通过杂交，获得了芥菜和埃塞俄比亚芥的种间杂种B. juncea × B. carinata（2n = BBAC），并结合基因分型、育性表型分型和细胞遗传学技术，在高育性选择条件下，鉴定了杂种在6代自花授粉后的情况。减数分裂配对行为从F1的68%二价体提高到S5/S6代的98%，最初的低育性也提高到与亲本物种相当的水平。第S5/S6代的杂种保留了完整的B套基因组（16个染色体），外加一个新的、稳定的A/C基因组（18～20个染色体），该套新的亚基因组是通过A和C套基因组的重组和重构获得的。本文的研究首次从实验证据上揭示了两个共享一套亚基因组的异源多倍体在杂交后，杂种中来自亲本的两套不同的基因组可以一起形成一套新的、重构的亚基因组。