Molecular cytogenetic and genomic analyses reveal new insights into the origin of the wheat B genome
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This work pinpointed the goatgrass chromosomal segment in the wheat B genome using modern cytogenetic and genomic technologies, and provided novel insights into the origin of the wheat B genome.
Wheat is a typical allopolyploid with three homoeologous subgenomes (A, B, and D). The donors of the subgenomes A and D had been identified, but not for the subgenome B. The goatgrass Aegilops speltoides (genome SS) has been controversially considered a possible candidate for the donor of the wheat B genome. However, the relationship of the Ae. speltoides S genome with the wheat B genome remains largely obscure. The present study assessed the homology of the B and S genomes using an integrative cytogenetic and genomic approach, and revealed the contribution of Ae. speltoides to the origin of the wheat B genome. We discovered noticeable homology between wheat chromosome 1B and Ae. speltoides chromosome 1S, but not between other chromosomes in the B and S genomes. An Ae. speltoides-originated segment spanning a genomic region of approximately 10.46 Mb was detected 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. Evidently, 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. These novel findings will facilitate genome studies in wheat and other polyploids.
We thank members of the labs involved for their help to this research and Drs. Lili Qi and Rebekah Oliver for their critical review of the manuscript. This project is supported by Agriculture and Food Research Initiative Competitive Grant no. 2013-67013-21121 from the USDA National Institute of Food and Agriculture.
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Conflict of interest
The authors declare that they have no conflict of interest.
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