It's hard to go anywhere without a map -- especially into the deep and complex world of genetics. Now, Kansas State University researcher Bikram Gill and an international team of researchers have developed a physical map of wheat's wild ancestor, Aegilops tauschii, commonly called goatgrass, as they take the first huge step toward sequencing the wheat genome -- a complete look at wheat's genetic matter.
A physical map of a genome shows the physical locations of genes and other DNA sequences of interest. Scientists use them to identify and isolate genes that are responsible for different traits, such as disease resistance and days to maturity.
The research was published in the April 22 edition of the Proceedings of the National Academy of Sciences (PNAS).
"Making a physical map is akin to breaking an egg and then assembling it back into a whole egg," said Gill, who is a university distinguished professor of plant pathology at K-State. "The wheat chromosome DNA is cloned in bacteria, millions of bits of DNA, which are sorted by robots and fingerprinted on sequencing machines and pseudochromosomal molecules are reassembled using powerful computers and algorithms."
"Wheat has the largest genome among crop plants and this is the biggest map as yet assembled for any organism, animal or plant," Gill said.
The work, which began 10 years ago, was supported by the U.S. National Science Foundation. K-State's portion of the $10 million funding totaled $2 million.
"Many years ago we discovered that a particular wheat ancestor -- Aegilops tauschii, commonly called goatgrass -- is a gold mine for wheat improvement," Gill said. "Wheat varieties grown in the Great Plains are protected from the leaf rust disease by genes extracted from goatgrass and from Hessian fly in the eastern U.S."
The physical map developed by the research team provides a roadmap for the mapping of genes that make wheat resistant to diseases, heat and drought and result in quality bread, Gill said, adding, " Most resistance genes seem to lie at the ends of chromosomes and can be easily accessed, leading to breeding of more productive and sustainable wheat varieties."
The next step in the process, Gill said, is to obtain funds to sequence the wheat genome, but added, "it's tough, in the tight budgetary situation we are in."
"Research is expensive and long term and we need to keep at it slowly and surely and not by 'stops and starts," Gill said. "We need to invest in research."
At stake is a crop worth billions of dollars to the United States and Kansas.
The dollar value of U.S. wheat production over the last six years (2007-2012) averaged $14.2 billion per year, according to U.S. Department of Agriculture data. In Kansas, the average dollar value per year over the same period was $2.101 billion.
- M.-C. Luo, Y. Q. Gu, F. M. You, K. R. Deal, Y. Ma, Y. Hu, N. Huo, Y. Wang, J. Wang, S. Chen, C. M. Jorgensen, Y. Zhang, P. E. McGuire, S. Pasternak, J. C. Stein, D. Ware, M. Kramer, W. R. McCombie, S. F. Kianian, M. M. Martis, K. F. X. Mayer, S. K. Sehgal, W. Li, B. S. Gill, M. W. Bevan, H. Simkova, J. Dolezel, S. Weining, G. R. Lazo, O. D. Anderson, J. Dvorak. A 4-gigabase physical map unlocks the structure and evolution of the complex genome of Aegilops tauschii, the wheat D-genome progenitor. Proceedings of the National Academy of Sciences, 2013; DOI: 10.1073/pnas.1219082110
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