Location: Cereal Crops ResearchTitle: Enriching and understanding the wheat B genome by meiotic homoeologous recombination Author
|Zhang, Wei - North Dakota State University|
|Zhang, Mingyi - North Dakota State University|
|Cao, Yaping - North Dakota State University|
|Zhu, Xianwen - North Dakota State University|
|Ren, Shuangfeng - North Dakota State University|
|Long, Yunming - North Dakota State University|
|Gyawali, Yadav - North Dakota State University|
|Cai, Xiwen - North Dakota State University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/27/2017
Publication Date: 8/7/2017
Citation: Zhang, W., Zhang, M., Cao, Y., Zhu, X., Ren, S., Long, Y., Gyawali, Y., Chao, S., Xu, S.S., Cai, X. 2017. Enriching and understanding the wheat B genome by meiotic homoeologous recombination [abstract]. National Association of Plant Breeders, August 7-10, 2017, Davis, CA.
Technical Abstract: Wheat, including common wheat (Triticum aestivum, 2n=6x=42, AABBDD) and durum wheat (T. turgidum ssp. durum, 2n=4x=28, AABB), contains three homoeologous subgenomes (A, B, and D) originated from three diploid ancestors. The wild einkorn wheat T. urartu (2n=2x=14, AA) contributed subgenome A and wild goatgrass Aegilops tauschii (2n=2x=14, genome DD) contributed subgenome D to wheat. The ancestor of subgenome B remains obscure even though the S genome of the goatgrass Ae. speltoides (2n=2x=14, SS) has been considered the one most closely related to the B genome. There are tremendous genetic variation in the wheat ancestral species and their relatives, which were mostly left out of modern wheat due to the allopolyploid origin of wheat. They represent an invaluable gene pool for wheat improvement. Here, we report our research progress toward expanding genetic variability of the wheat B genome using Ae. speltoides and the tall wheatgrass Thinopyrum elongatum (2n=2x=14, genome EE), and determining homology of the individual B-S homoeologous pairs by comparative meiotic pairing and SNP analyses. Wheat ph1b mutant was used to induce B-S and B-E homoeologous meiotic pairing/recombination in the specially constructed genotypes. The wheat 90K SNP arrays and SNP-derived STARP (semi-thermal asymmetric reverse PCR) marker analysis were performed to recover B-S and B-E homoeologous recombinants. To date, we have screened a total of 5,817 individuals from the B-S and B-E homoeologous recombination populations and identified 858 recombinants involving different chromosomal regions in 11 homoeologous chromosome pairs, i.e. 1B-1S, 1B-1E, 2B-2S, 2B-2E, 3B-3E, 4B-4S, 5B-5S, 5B-5E, 6B-6S, 6B-6E, and 7B-7S. The Ae. speltoides- and Th. elongatum-derived resistance genes for rusts, tan spot, Stagonospora nodorum blotch (SNB), and scab diseases and tolerance genes for salt and waterlogging have been incorporated into the wheat B genome through induced homoeologous recombination. All the recombinants were physically delineated by genomic in situ hybridization (GISH). Integrative analysis of the SNP and GISH data for the recombinants physically mapped the SNPs to the individual B-genome chromosomes. This work developed alien introgression lines containing the genes of interest as well as a large set of homoeologous recombinants involving wheat B-genome chromosomes. They are novel germplasm for wheat improvement and useful genomics resources for various genome studies in wheat. In addition, we discovered an Ae. speltoides-originated segment spanning a genomic region of approximately10.57 Mb on the long arm of wheat chromosome 1B (1BL). The Ae. speltoides-originated segment on 1BL was found to co-evolve with the rest of the B genome. Therefore, Ae. speltoides had been involved in the origin of the wheat B genome, but should not be considered an exclusive donor of this genome. The wheat B genome might have a polyphyletic origin with multiple ancestors involved, including Ae. speltoides. Meanwhile, we have been deploying the ph1b deletion mutant in the major classes of US wheats and developing ph1b deletion-specific molecular markers. This will facilitate meiotic homoeologous recombination-based gene introgression from wild grasses directly into US wheats and extend the genetic variability of US wheats.