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with a combine harvester in the background Pascal Rossignol / Reuters
will make it much easier to breed new varieties of the world's
most important crop.
But only now has the long-awaited wheat genome (Shifting the Limits in Wheat Research and Breeding using a Fully Annotated Reference Genome) been fully sequenced.
That delay says nothing about wheat's importance. It is arguably the most critical crop in the world. It's grown on more land than anything else. It provides humanity with a fifth of our calories.
But it also has one of the
most complex genomes known to science.
Just one of wheat's chromosomes - 3B - is bigger
than the entire soybean genome.
After humans domesticated this plant and planted it in their fields, a third grass species inadvertently joined the mix.
This convoluted history has left modern bread wheat
with three pairs of every chromosome, one pair from each of the
three ancestral grasses. In technical lingo, that's a
hexaploid
genome. In simpler terms, it's a gigantic pain in the ass.
But if each chromosome occurs six times, how do you know
where to put any given piece?
It's like solving a giant jigsaw puzzle that depicts the same patch of blue sky three times over.
After 14 years, around $75 million, and a few incomplete drafts, the team has now published the nearly complete genome of a wheat variety called Chinese Spring (Wheat Breeding in the hometown of Chinese Spring), mapping more than 107,000 of its genes.
Unexpectedly, a much smaller six-person team, led by Steven Salzberg from Johns Hopkins University, released its own version of a near-complete wheat genome last year, by using new technologies that read out very long stretches of DNA.
But while Kellye Eversole applauds the small team's accomplishment, she notes that its version,
By contrast, wheat production has lagged behind, and the crop's profitability has recently dropped.
That's problematic because researchers estimate that the world will need to grow 60 percent more wheat by 2050 to feed its booming population.
Alison Bentley is the director of genetics and breeding at the United Kingdom's National Institute of Agricultural Botany, and although she says that people have made huge progress in breeding wheat in the absence of a genome, having one will speed everything up.
Traditionally, it has taken a lot of trial and error to create new varieties of wheat that, say, tolerate cold or resist fungal diseases.
But with a full genome at hand, breeders can identify the genes behind particular traits, and ensure that these are present in their crops.
This is already happening.
Using the completed genome, the team identified a long-elusive gene (with the super-catchy name of TraesCS3B01G608800) that affects the inner structure of wheat stems.
If plants have more copies of the gene, their stems are solid instead of hollow, which makes them resistant to drought and insect pests.
By using a diagnostic test that counts the gene, breeders can now efficiently select for solid stems.
The IWGSC has also started to work out when different genes are turned on as wheat germinates and grows, and how these patterns of activity vary across the three sub-genomes.
If scientists can figure out how to switch on specific genes at particular points in the plant's life cycle, people could potentially breed wheat in real time,
Her only word of caution is that the new genome comes from an unusual variety, Chinese Spring, which,
Still, Chinese Spring is historically important as the foundation of a lot of early wheat research.
And now that its genome is out, it'll be much easier for scientists to sequence a wider range of cultivars, and understand the genetic underpinnings of different traits.
Researchers might also be able to more easily temper the 'dark side' of wheat.
Many people are allergic to glutens and other wheat proteins, leading to disorders like,
Scientists have managed to identify many of the specific proteins responsible,
His team has now identified 356 such genes.
Of these, 127 are new to science, and 222 were known but had been incorrectly sequenced.
The team also found that wheat produces more of the allergens behind celiac disease when grown at high temperatures, which suggests that baked goods might become more allergenic as the world continues to 'warm.'
But perhaps, by understanding the genes behind such allergens, breeders will be able to counteract that trend and create less-allergenic varieties.
Of course, it's unlikely to be that simple.
Odd-Arne Olsen notes that the same proteins behind wheat allergies also determine the baking quality of flour.
Similarly, Eversole notes that wheat varieties that contain more protein also tend to grow at lower yields. There are always trade-offs, but the team hopes that a full genome will make it easier to navigate them.
Using the genome, breeders could also use gene-editing techniques like CRISPR to rapidly alter the traits of their crops.
The IWGSC showed how easy this could be by identifying wheat genes that influence flowering time, and altering them with CRISPR to create varieties that bloom a few days earlier than usual.
These techniques could also be used to move beneficial traits from wild wheat species into domestic strains. The main hurdles to such changes are public approval and regulatory restrictions.
Last month, the European Union's highest court ruled that CRISPR-edited crops count as 'genetically modified organisms,' even if they don't involve introducing genes from other organisms.
Such crops will now face a long and expensive approval process that will likely discourage many companies from investing in them.
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