Preferential Subgenome Elimination and Chromosomal Structural Changes Occurring in Newly Formed Tetraploid Wheat- Aegilops ventricosa Amphiploid (AABBD v D v N v N v ).

Artificial allopolyploids derived from the genera Triticum and Aegilops have been used as genetic resources for wheat improvement and are a classic example of evolution via allopolyploidization. In this study, we investigated chromosomes and subgenome transmission behavior in the newly formed allopolyploid of wheat group via multicolor Fluorescence in situ hybridization (mc-FISH), using pSc119.2, pTa535, and (GAA) ₇ as probe combinations, to enabled us to precisely identify individual chromosomes in 381 S ₃ and S ₄ generations plants derived from reciprocal crosses between Ae. ventricosa (D ^v D ^v N ^v N ^v ) and T. turgidum (AABB). A higher rate of aneuploidy, constituting 66.04-86.41% individuals, was observed in these two early generations. Of the four constituent subgenomes, D ^v showed the highest frequency of elimination, followed by N ^v and B, while A was the most stable. In addition, structural chromosomal changes occurred ubiquitously in the selfed progenies of allopolyploids. Among the constituent subgenomes, B showed the highest number of aberrations. In terms of chromosomal dynamics, there was no significant association between the chromosomal behavior model and the cytoplasm, with the exception of chromosomal loss in the D ^v subgenome. The chromosome loss frequency in the D ^v subgenome was significantly higher in the T. turgidum × Ae. ventricosa cross than in the Ae. ventricosa × T. turgidum cross. This result indicates that, although the D subgenome showed great instability, allopolyploids containing D subgenome could probably be maintained after a certain hybridization in which the D subgenome donor was used as the maternal parent at its onset stage. Our findings provide valuable information pertaining to the behavior patterns of subgenomes during allopolyploidization. Moreover, the allopolyploids developed here could be used as potential resources for the genetic improvement of wheat.
(Copyright © 2020 Zhang, Yang, Jiang, Guo, Wang, Zhu, Li, Wan, Wang, Deng, Xuan and Yang.)