Rust resistant wheat: it’s a package deal

By Janna Moats

Dr. Wentao Zhang (Research Officer) and Kerry Boyle (Technical Officer) at the National Research Council of Canada are revolutionizing wheat breeding programs through their genetic research.

Using genetic packaging, they have curated the ideal recipe for durable multi-rust resistance in Canadian wheat.

Generating new crop varieties through conventional breeding systems is an expensive and laborious process. Years are spent observing and selecting desired plant traits (phenotyping) and then linking those traits to specific genes (genotyping). In the end, hundreds of individual genes can be linked back to a single trait, with little understanding of their relative importance.

According to Dr. Zhang, the current process for developing new crop varieties is like baking a cake without a recipe.

“Its kind of a blind approach,” said Dr. Zhang. “You try different combinations of different ingredients until you get something resembling a cake. But if you had a recipe that told you what ingredients to use and how much, you would end up with a much better cake.”

To advance crop breeding programs, Dr. Zhang and Boyle set out to create the best possible recipe for achieving durable multi-rust resistance in wheat.

The first challenge was to narrow down the list of genetic ingredients.

“There are lots of genes associated with leaf rust, stem rust, and stripe rust,” explained Dr. Zhang.

In fact, there are over two hundred!

It would be impossible for crop breeders to include all these genes into a plant. So, Dr. Zhang and Boyle needed to identify the best of the best.

Fortunately, they had some help.

“We had some great collaborations with Agriculture and Agri-Food Canada, as well as the University of Saskatchewan,” said Boyle. The team also received support through Sask Wheat and the Saskatchewan Ministry of Agriculture’s Agriculture Development Fund.

First, Dr. Zhang and Boyle crossed two known varieties of wheat with different susceptibilities to rust (Thatcher x Parula). Then they used genetic mapping to identify which genes are most associated with multi-rust resistance and where they are located within the plant genome. Finally, they came up with their “top-picks” for genetic markers for durable resistance to rust.

When it comes to generating durable multi-rust resistance in wheat, these genes work best as a packaged deal. “It’s an additive effect that really makes the difference,” said Boyle.

This information is extremely valuable to crop breeders. By testing the primary genetic material, they will know whether their plants will have resistance right from the start.

“Breeders can skip some of the steps in their breeding program if they know that this package of resistance genes is present,” explained Boyle. This amounts to saved time and saved costs.

Identifying genetic packages also gives breeders information as to which markers to preserve.

“We want to make sure we don’t lose good genes in new cultivars,” said Dr. Zhang. “If you don’t know what genes to look for, you might lose them.”

When it comes to rust diseases, many western Canadian wheat varieties are already resistant to some degree. So why did Dr. Zhang and Boyle make it the focus of their research?

“It’s a proactive approach,” explained Dr. Zhang.

Climate change is bringing new disease threats to Canada, including new races of rust.

“Previously, we didn’t have to worry about how rust evolved or how it was growing in other places, like Mexico,” said Boyle. “But now, with climate change, these things are blowing up the corridor and are a risk to Canada.”

Dr. Zhang hopes their gene packaging approach will inspire a new era of crop development and will support long-term sustainability of the wheat industry.