Meiotic homoeologous recombination-based mapping of wheat chromosome 2B and its homoeologues in Aegilops speltoides and Thinopyrum elongatum

Authors: ZHANG, WEI - North Dakota State University; ZHU, XIANWEN - North Dakota State University; ZHANG, MINGYI - North Dakota State University; Chao, Shiaoman; Xu, Steven; CAI, XIWEN - North Dakota State University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2018
Publication Date: 8/14/2018
Citation: Zhang, W., Zhu, X., Zhang, M., Chao, S., Xu, S.S., Cai, X. 2018. Meiotic homoeologous recombination-based mapping of wheat chromosome 2B and its homoeologues in Aegilops speltoides and Thinopyrum elongatum. Theoretical and Applied Genetics. 31(11):2381–2395. https://doi.org/10.1007/s00122-018-3160-0.
DOI: https://doi.org/10.1007/s00122-018-3160-0

Interpretive Summary: Homologous recombination is referred to as the genetic exchange of DNA sequences between two identical chromosomes, whereas homoeologous (i.e., partially homologous) recombination is type of genetic recombination between two homoeologous chromosomes. In this study, we aimed to use homoeologous recombination to map a wheat chromosome and its two homoeologous chromosomes from goatgrass and tall wheatgrass. Through precise genetic manipulation, we developed 199 wheat lines carrying the genetic exchanges between the wheat chromosome and the two grass chromosomes. By using these lines, we developed a chromosome map by assigning 1,037 DNA markers onto the distinct regions of the three chromosomes. This chromosome map is useful for the genome studies of wheat and its relatives while the wheat lines carrying the chromosome segments transferred from goatgrass and tall wheatgrass are a valuable genetic resource for wheat improvement in breeding.

Technical Abstract: The polyploid origin of common wheat led to a large and complex genome with narrow genetic diversity and low polymorphism. This has limited the homologous recombination-based genome studies in wheat. Here, we aimed to exploit meiotic homoeologous recombination for molecular mapping of wheat chromosome 2B and its homoeologue 2S from Aegilops speltoides and 2E from Thinopyrum elongatum in this study. The 2B-2S and 2B-2E recombination was induced by the ph1b mutant, and recovered using molecular markers and genomic in situ hybridization (GISH). A total of 112 2B-2S and 87 2B-2E recombinants involving different chromosome regions were developed, and physically delineated by GISH. The 2B-2S and 2B-2E recombination hotspots mapped to the subterminal regions on both arms. Interestingly, we found that the recombination hotspots with the highest recombination rates were located on the short arms. Eighty-three 2B-2S and 67 2B-2E recombinants were genotyped using the wheat 90K SNP arrays. Based on the genotyping results and GISH patterns of the recombinants, chromosomes 2B, 2S, and 2E were partitioned into 93, 66, and 46 bins, respectively. Totally, 1,037 SNPs physically mapped onto the distinct bins of these three homoeologous chromosomes. A homoeologous recombination-based bin map was constructed for chromosome 2B, providing a unique physical framework useful for the genome studies of wheat and its relatives. In addition, meiotic homoeologous recombination leads to gene introgression to diversify the wheat genome for germplasm development. Therefore, homoeologous recombination-based studies enhance understanding of the wheat genome and its homoeologous counterparts from wild grasses, and expand the genetic variability of the wheat genome.