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‘Shotgun’ method sorts through wheat genome

UC DAVIS (US) — To amp up wheat’s yield and nutritional content, scientists are unraveling the complex history hidden in its genome, which is five times the size of humans’.

“This work moves us one step closer to a comprehensive and highly detailed genome sequence for bread wheat, which along with rice and maize is one of the three pillars on which the global food supply rests,” says study author Jan Dvorak, professor of plant sciences at University of California, Davis.

“The world’s population is projected to grow from 7 billion to 9 billion by 2050,” he says. “It is clear that, with no new farmable land available to bring into cultivation, we must develop higher-yielding varieties of these three cereals to meet the growing global demand for food.”

The bread wheat genome is especially complex because bread wheat originated from three ancient grass species. Its genome is, therefore, a composite of three genomes.

Wheat geneticists have historically designated the genomes of those parent grasses as the A, B, and D genomes, each containing a similar set of genes. As a result, most bread wheat genes exist in triplicate.

To aid the sequence assembly of bread wheat, Dvorak and colleagues have worked with scientists at the US Department of Agriculture’s Agricultural Research Service and with scientists at two other US institutions on sequencing of the genome of the parent species Aegilops tauschii—the source of the bread wheat D genome.

The US team shared the Aegilops tauschii sequences with researchers at the Biotechnology and Biological Sciences Research Council of England, which was assembling all three of the wheat A, B, and D genomes.

Comparing the Aegilops tauschii sequence with modern wheat allows researchers to assess genomic changes that have taken place in bread wheat since its origin approximately 8,000 years ago.

In the study reported today in Nature, the researchers used the whole genome “shotgun sequencing” approach, which generates billions of random genome sequence “reads” and then pieces them together.

The results provide information about the DNA making up wheat genes that will help wheat breeders develop hardier varieties by linking genes to key traits, such as disease resistance and drought tolerance.

“This sequencing effort has yielded important information that will accelerate wheat genetics and breeding and help us better understand wheat evolution,” Dvorak says.

“It cannot be overemphasized, however, that this is just one step in the global effort to produce a high-quality draft of the bread wheat genome sequence.”

He says completion of such a high-quality genome sequence for bread wheat is still a few years away and will require broad international collaboration to complete.

Additional investigators contributed from UC Davis, USDA, Kansas State University, Cold Spring Harbor Laboratory in New York, University of Liverpool, University of Bristol, John Innes Centre, and European Bioinformatics Institute.

The Biotechnology and Biological Sciences Research Council of England, the USDA’s National Institute of Food and Agriculture, The Royal Society, the German Ministry of Education and Research, and the National Science Foundation provided funding for the study.

Source: UC Davis

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