Frequent numerical and structural chromosome changes in early generations of synthetic hexaploid wheat

Authors: ZHANG, SIYU - Nanjing Agricultural University; DU, PEI - Nanjing Agricultural University; LU, XUEYING - Nanjing Agricultural University; FANG, JIAXIN - Nanjing Agricultural University; WANG, JIAQI - Nanjing Agricultural University; CHEN, XUEJUN - Nanjing Agricultural University; CHEN, JIANYONG - Nanjing Agricultural University; WU, HAO - Nanjing Agricultural University; YANG, YANG - Nanjing Agricultural University; TSUJIMOTO, HISASHI - Nanjing Agricultural University; Chu, Chenggen; QI, ZENGJUN - Nanjing Agricultural University

Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2021
Publication Date: 12/16/2021
Citation: Zhang, S., Du, P., Lu, X., Fang, J., Wang, J., Chen, X., Chen, J., Wu, H., Yang, Y., Tsujimoto, H., Chu, C.N., Qi, Z. 2021. Frequent numerical and structural chromosome changes in early generations of synthetic hexaploid wheat. Genome. https://doi.org/10.1139/gen-2021-0074.
DOI: https://doi.org/10.1139/gen-2021-0074

Interpretive Summary: Modern bread wheat evolved from a hybrid of emmer wheat and wild goatgrass approximately eight thousand years ago. During the process of evolution, variation in chromosome size and number was the main source of reforming the wheat genome and diversifying wheat genetic background. However, how these chromosome variations occurred and their roles in expanding wheat genetic diversity are mostly unknown. ‘Synthetic wheat’ can be produced by crossing durum wheat with wild goatgrass that imitates the origin of bread wheat. Therefore, synthetic wheat lines are ideal materials for studying the role of chromosomal variations in wheat evolution. By using various molecular techniques, we analyzed a set of synthetic wheat lines to identify chromosome variations and to track their transmission during two successive generations. We found that chromosome structural variations can induce variations in chromosome numbers, and vice versa, that chromosome numerical variations also induced structural variations. This study shows that both structural and quantitative chromosomal variations played important roles in wheat evolution and several specific chromosomes were more actively involved in the process. In addition, synthetic wheat plants from this study carry genetic variations that can be used to improve the genetic basis of modern wheat lines.

Technical Abstract: Chromosome variations play important roles in the evolution of allopolyploid plant species. The modern allohexaploid wheat (Triticum aestivum, 2n = 6x, AABBDD) involves many structural chromosome variations though the way and the time about the occurrence of those variations remains unknown. The artificially induced synthetic hexaploid wheat (SHW) lines provided the opportunity of investigating chromosome variations that could imitate the evolution process during formation of modern wheat in the early time. By using cytological and molecular markers, this study clustered 12 SHW lines derived from crossing durum wheat cultivar ‘Landgon’ (T. durum, 2n = 4x, AABB) with 12 accessions of Ageliops tauschii (2n = 2x, DD) into different groups. Among 702 plants from two successive generations S8 and S9, 415 (59.12%) carried chromosome variations including those showed changes in numerical (179), structural (111) and other complex ones (125). The variations involved all 21 chromosomes from A, B and D sub-genomes with overall variation frequency varied in each chromosome from each sub-genome. Among them, chromosomes from D sub-genome showed the highest frequency (34.62%) for variation, and then in sub-genomes B (27.49%) and A (13.11%). Chromosomes 1B, 4D, 4B, 5A and 1D varied more than the others. The total chromosome variation frequency of each SHW varied from 8.33% to 100.00% in S8 and 16.67% to 100.00% in S9, respectively, but no significant difference was identified among the three cluster groups which were categorized by either cytological or molecular markers. Frequent and non-random chromosome variations generally occurred in all SHW lines, indicating an important driving power for synthetic hexaploid wheat evolution. These findings provide new information and genetic stocks for wheat breeding using SHW as parents.