The wheat genome. A scientific revolution or a step forward in wheat breeding?

The Portland Winterhawks.

The Seattle Thunderbirds and the Red Deer Rebels.

The Western Hockey League has many teams with catchy and memorable names.

But one stands above the rest – the Brandon Wheat Kings.

The name captures the historic importance of wheat to Western Canada and, for good measure, it’s the title of an iconic song from an iconic Canadian band – The Tragically Hip.

Given Brandon’s connection to wheat, it’s fitting that AAC Brandon is the most popular spring wheat in Western Canada.

In 2020, AAC Brandon was planted on 42 per cent of the 11.2 million acres of Canadian Western Red Spring wheat on the Prairies. Farmers love it because the semi-dwarf variety produces high protein and generous yields, even when the weather doesn’t co-operate.

“In 2017 and 2018 the weather was hot and dry, and the yields growers were seeing from AAC Brandon kept going up,” said Todd Hyra, business manager Western Canada for Secan, the largest supplier of certified seed to Canadian farmers and distributor of AAC Brandon. “We had areas with only a few inches of rainfall and we were hearing stories of 80-plus bushels per acre, which you didn’t see or hear of in hot, dry conditions at the time.”

Those extra bushels mean tens of millions in extra cash for prairie wheat growers. Assuming AAC Brandon yields are three to five bushels higher than older varieties:

• 4.7 million acres of AAC Brandon

• 3- 5 more bu. per acre

• $6.50 per bu.

• = $90 – $150 million

That’s a sizable financial bonus, thanks to a superior wheat variety, but it took more than a decade for Canadian farmers to realize those benefits.

AAC Brandon was derived from a cross of two varieties, made in 2003 at Agriculture Canada’s research station in Swift Current, Sask. It required 11 years of research and testing to get Brandon to market in the fall of 2014.

Surely, there must be a better way to introduce a new variety of wheat, so farmers are prepared for the extreme weather and associated risks that may come with climate change.

That’s the promise of a global effort, of scientists from North America, Europe, Australia and elsewhere. In November, the group announced they had sequenced the genomes of 15 varieties of wheat. The discovery builds upon previous research on wheat genetics.

This newfound knowledge of wheat genetics could lead to new varieties that are resistant to emerging insect pests. Maybe a new type of wheat that can tolerate dry Saskatchewan summers with 30 mm of rain and soaking wet years with 300 mm of precipitation.

How will breeders use the genomic sequences?

Ron Knox, a wheat biotechnology and pathology expert with Agriculture Canada in Swift Current, Sask, described the genomic sequencing of 15 varieties as a “vast library” of information.

“The volume of information generated, it’s really unimaginable… in a way,” said Knox, who described the work of wheat geneticists is ‘upstream’ research.

Wheat breeders do ‘applied’ research.

The DNA of wheat is a very, very long list of four letters – A,C,G and T. Those letters connect in the double helix, to form the genetic code of a wheat variety.

In the case of bread wheat, there are about 17 billion base pairs in its genome. The human genome has about three billion base pairs.

Using Knox’s library analogy, the wheat geneticists who sequenced the 15 varieties have written the books in the library.

The wheat breeders need to take the information in those hundreds of books and do something useful with it. That is, produce a commercial wheat variety with higher or more consistent yields in an era of unpredictable weather.

But to apply the information within the library, wheat breeders need to know what book they’re looking for.

“That’s been a limitation in wheat because of the complexity of the genome,” Knox said. “We don’t actually know too many genes at this point and how they influence traits.”

Gene

As an example of how breeders could use the genomic sequencing information, let’s assume climate change increases annual rainfall on the Prairies and a new wheat pathogen, called disease X, suddenly appears in 2027.

A wheat variety from China might have resistance to disease X. Breeders could then pinpoint the gene (or genes) in the code of the Chinese variety that provide resistance.

That’s where a new tool called gene editing comes into play.

To create resistance to disease X in a popular variety like Brandon, breeders could identify the genetic code in Brandon that confers susceptibility to the disease.

Knowing the genes and order of A,C,G,T in the Chinese wheat that provides resistance, scientists could ‘edit’ the Brandon code so that it’s also resistant to disease X.

That direct approach is interesting, but many genes are usually responsible for complex traits like disease resistance, said Richard Cuthbert, a wheat breeder and Knox’s colleague at Agriculture Canada in Swift Current.

Is gene editing the future of wheat breeding?

Last May, the United States Department of Agriculture announced that gene-edited crops will be treated similarly to conventional plant breeding and will be largely exempt from regulation. National regulators in Japan, Argentina and Australia have adopted similar positions

Canada’s crop science industry is hoping the federal government follows the American’s lead, but the feds haven’t taken a position on the technology.

Regulation of a gene-edited wheat is one thing, public acceptance is another.

For millions around the world – bread is life.

“It always comes down to end-use market acceptability,” said Ellen Sparry, general manager of C&M Seeds in Palmerston, Ontario.

For example, the recent development of a GMO drought-tolerant wheat in Argentina is far more appropriate for growers there, where drought is a common occurrence.

“But the consumer has to accept this, as well. Wheat’s seen as ‘wholesome’ and until consumers accept a GM wheat variety – (even) if it has a trait like Golden Rice –it’s hard to envision.”

A gene-edited wheat variety is not the same as genetically modified wheat, but explaining the scientific nuance to consumers could prove challenging.

“In Canada, there’s a lot of dialogue around food safety, politics and more emphasis on public perception,” adds Sparry.

Will gene editing replace traditional wheat breeding?

Knox and Cuthbert responded the same way to this question.

No.

Traditional wheat breeding will remain critical to the process, Knox said.

Gene editing will become another ‘tool in the toolbox’ for wheat scientists, not the only tool.

One reason is that wheat varieties must be bred and adapted to specific environmental conditions. A wheat that performs well in Texas probably isn’t suited for northern Saskatchewan.

Knox Interview

Another reason is that traditional breeding can improve multiple traits, yield, straw strength, pest resistance, at the same time.

There’s also the matter of serendipity.

Or, luck of the draw.

Gene editing can precisely re-arrange the A,C,G,T in a small portion of wheat’s genetic code. But there’s about 120,000 genes in bread wheat. Crossing two varieties may scramble the genetic code in an unexpected way and produce some magic – like a five per cent boost in yield.

“In wheat breeding we’ve gotten pretty darn quick, once you make a cross, and then you can select for a lot of traits,” said Cuthbert, who was part of the team that developed AAC Brandon.

“A variety we just released… it’s registered as AAC Hockley, it took seven years to develop.”

Seven years isn’t really quick, but good science takes time and is usually incremental. Researchers build upon a previous discovery and make small improvements.

That could be the main outcome of sequencing 15 varieties of wheat – a massive opportunity for incremental improvements.

Wheat breeders will use the new -found genomic information, for years, to understand what the genes do and how they differ from variety to variety, Knox said.

“So we can see what’s going on with the sequence… and use selectable markers that we can apply to breeding material.”

As for genome editing, wheat breeders may use it to edit the genes of parent varieties for crosses.

Or, to directly fix weaknesses in existing varieties.

But crossing the genetics of two wheat varieties will always be exponentially more powerful than gene editing.

“I don’t know if Ron Knox mentioned this, but it’s something he told me when I started at Swift Current,” Cuthbert said. “You can take 120,000 genes and if you… could get them into every combination possible, there would be more combinations than there are atoms in the universe.”

Contributors: Robert Arnason, Ralph Pearce