Location: Cereal Crops ResearchTitle: Delimitation of wheat ph1b deletion and development of ph1b-specific DNA markers
|Gyawali, Yadav - North Dakota State University|
|Zhang, Wei - North Dakota State University|
|Cai, Xiwen - North Dakota State University|
Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2018
Publication Date: 1/1/2019
Citation: Gyawali, Y., Zhang, W., Chao, S., Xu, S.S., Cai, X. 2019. Delimitation of wheat ph1b deletion and development of ph1b-specific DNA markers. Journal of Theoretical and Applied Genetics. 132(1):195–204. https://doi.org/10.1007/s00122-018-3207-2.
Interpretive Summary: Higher organisms can be classified as a diploid or polyploid species based on the number of paired (homologous) sets of chromosomes. Diploid species contain only one genome in which two sets of chromosomes are derived from two parents, respectively, whereas polypoid species have more than two sets of chromosomes. Wheat is a polyploid species containing three closely related genomes (i.e. A, B, and D). However, wheat behaves in a diploid-like manner where chromosome pairing and recombination occur only between homologous (identical) chromosomes due to the presence of a gene controlling chromosome pairing. This gene maintains the stability of the wheat genome by preventing pairing between homoeologous (i.e., partially homologous) chromosomes such as 1A and 1B. A wheat line containing a deletion of this gene has been widely used to induce homoeologous recombination for gene introgression from wild grasses into wheat. However, the actual size and location of the deletion remains undetermined. In the present study, we determined the location of the deletion in the wheat genome and developed user-friendly DNA markers specific to track it. These new markers will improve the efficacy in using the deletion line for gene introgression and genomic studies in wheat and its relatives.
Technical Abstract: The Ph1 (pairing homoeologous) locus has been considered a major genetic system for the diploidized meiotic behavior of the allopolyploid genome in wheat. It functions as a defense system against meiotic homoeologous pairing and recombination in polyploid wheat. A large deletion of the genomic region harboring Ph1 on the long arm of chromosome 5B (5BL) led to the ph1b mutant in hexaploid wheat ‘Chinese Spring’ (CS), which has been widely used to induce meiotic homoeologous recombination for gene introgression from wild grasses into wheat. However, the breakpoints and actual physical size of the deletion remain undetermined. In the present study, we first anchored the ph1b deletion on 5BL by the high-throughput wheat 90K SNP assay, and then delimited the deletion to a genomic region of 60,014,523 bp by chromosome walking. DNA marker and sequence analyses detected the nucleotide positions of the distal and proximal breakpoints (DB and PB) of the ph1b deletion and the deletion junction as well. This will facilitate understanding of the genomic region harboring the Ph1 locus in wheat. In addition, we developed user-friendly DNA markers specific for the ph1b deletion. These new ph1b deletion-specific markers will dramatically improve the efficacy of the ph1b mutant in the meiotic homoeologous recombination-based gene introgression and genome studies in wheat and its relatives.