Genetic knowledge provides tools to meet wheat growers’ challenges

Researchers from around the globe gathered in Saskatoon this month, focused on making wheat more efficient and sustainable using the latest in breeders’ tools.

In August 2018, the International Wheat Genome Sequencing Consortium published the first reference genome of bread wheat, followed in April of 2019 with the genome for durum.

Curtis Pozniak, a researcher and durum breeder at the University of Saskatchewan, was part of the effort by more than 200 scientists from 73 organizations in 20 countries. He said this new knowledge makes it easier to find variations that could yield valuable traits.

“Obviously Fusarium head blight is the thing we’re working very hard to improve,” Pozniak said. “We heard talks on managing fusarium resistance in wheat, including durum.”

There’s a lot of interest in wheat. Pozniak was chair of the International Wheat Congress held in Saskatoon in July. The week-long event drew 890 delegates from 52 countries.

Genome Canada and the University of Saskatchewan took advantage of the international audience to announce funding for several projects including 4DWheat: Diversity, Discovery, Design and Delivery. Led by Pozniak and Sylvie Cloutier, a molecular geneticist from Agriculture Canada, the $14.2 million project aims to identify new sources of genetic variation in wheat and use advanced techniques to incorporate useful genes into new varieties.

While Pozniak said these new techniques won’t necessarily get new varieties into farmers’ hands quicker, they will allow researchers to more quickly identify dead ends, for example, with a simple DNA test.

“I like to think of it more as efficiency of the breeding process,” Pozniak said. “Being able to efficiently select for disease resistance or agronomic traits that our producers are interested in, even the end-use quality profiles.”

Pozniak and Cloutier work with genomic tools that spark little public concern. Other wheat breeders use techniques that transfer genes between different plants, or use gene-editing techniques such as CRISPR.

For example, researchers have discovered that certain species of tropical grass have evolved the ability to produce chemicals around their roots that keep nitrogen in the soil close at hand, available for when the plant needs it. These grasses use almost all of the available nitrogen in the soil.

Adding this trait to wheat would benefit both the environment and farmers’ bottom lines, as current varieties only use about half of the nitrogen fertilizer applied, with the rest either ending up in surface and ground water or as nitrous oxide, a greenhouse gas.

Getting these genes into wheat quickly will require advanced techniques.

Jorge Dubcovsky, a wheat breeder at the University of California, Davis, said new gene-editing techniques make it easier and faster to develop new varieties with genetic advantages.

Unfortunately, many of these methods face significant pushback, as they are regarded as GM and thus face significant hurdles in terms of regulations and public acceptance.

Dubcovsky said such concerns are unfounded from a scientific point of view. Traditional mutagenesis used since the early 1900s randomly changes genes, yet these crops face no special regulation. CRISPR gene editing is far more precise but is heavily regulated, particularly in the European Union.

“CRISPR is the same thing but instead of producing millions of mutations and you don’t know where they are, you can go to a precise place in the chromosome and direct the mutagenesis to a single point,” Dubcovsky said. “I have zero concern about off-target effects.”

The International Maize and Wheat Improvement Center (CIMMYT) estimates that wheat provides 20 per cent of the calories and 20 per cent of the protein in the human diet, making it essential to food security world-wide. The organization, which develops and distributes wheat for farmers around the world, estimates its varieties produce more than half of the wheat grown in the developing world.

The demands of changing climate, growing populations, plant pests and diseases mean wheat breeders are pressed for time.

Dubcovsky uses the example of Ug99, a virulent wheat stem rust that can completely wipe out a crop in a few weeks. Now present in several African countries and the Middle East, it’s expected to spread.

Resistance genes for Ug99 have been discovered in wild relatives of wheat, but getting them into wheat quickly means using tools not allowed in Europe and some parts of Africa. It’s particularly irritating to Dobcovsky, since there is no difference between a CRISPR mutation and one produced by older methods.

“That limits what you can use and the benefits we can create,” he said. “Not as a company that can make money, but as a public researcher that wants to help you. You are telling us, ‘give me something, help me to solve the problem’ and you tie my hands behind the back and say, ‘you can’t do it that way. You have to do it the difficult way.’”

“The more tools you give us, the faster and further we will go.”

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