Â鶹ÒùÔº

Bacteria, viruses and fungi are masters at evolving new strategies to infiltrate plants and cause disease that harm crops. To get ahead of these pathogens, University of Saskatchewan (USask) researchers like Dr. Valentyna Klymiuk (Ph.D.) and Dr. Curtis Pozniak (Ph.D.) are studying wild wheat varieties that carry resistance to these harmful pathogens. This led them to discover something they'd never encountered before—a unique pair of genes that work together to protect against disease.

To support its variety development program, USask's Crop Development Center (CDC) has been diving back into the gene pool of wheat and screening its wild relatives for useful traits that can be effectively deployed in new wheat cultivars.

Wild wheat has not been domesticated, so it cannot be used directly in breeding, but it contains useful diversity to respond to environmental threats. This makes it ideal for learning new methods of crop resistance.

Research at the CDC focuses on improving crop varieties. By integrating basic research into crop breeding, the CDC translates scientific discoveries into new high-yielding varieties that can be used by growers.

"Part of our research is keeping one step ahead of pathogens by identifying new resistance genes which ideally could be stacked, like Lego blocks, so the pathogen can't easily overcome the resistance," said Klymiuk.

Looking deeper into a wild strain of wheat, Klymiuk and Pozniak found that it demonstrated significant resistance to stripe rust, a type of fungal infection that is one of the top five diseases of concern for producers. Klymiuk and Pozniak soon realized that the resistance they identified in this wild strain was behaving differently than expected.

Their findings were published in .

"Once we started assessing the resistance, we could see that it was different to others that we have studied before. The resistance was acting in an atypical way, which signaled a very different plant response," said Pozniak, professor and director of the CDC at USask. "We were quite intrigued about what was really going on."

Klymiuk, a research officer in Pozniak's program, said that typically one gene is responsible for the expression of a stripe rust, but in the case of this wild wheat, they determined that two genes working together as a pair were required for full resistance. One gene is responsible for sensing the invading pathogen while the other activates the immune response of the plant to stop the pathogen in its tracks.

To confirm which genes were responsible for resistance, Klymiuk's experiments turned each of the genes "off" like flipping the breaker to see which room of the house goes dark. When the gene is switched "off" the plant can no longer protect itself and becomes susceptible to the pathogen. However, this unique gene pair proved to be a bit of an anomaly, which caused a hiccup in the researcher's results.

"Initially, we thought only a single gene was responsible. Most of our results made sense but there were a few plants that didn't give us the expected results. This was a head scratcher, so we went back to rethink our experiments and to test if two genes were actually involved. Once we retested, the results became clear," said Klymiuk.

The team dug deeper and found that the two outlier genes interact at a protein level, physically coming together to initiate the resistance response.

"A lot of the time when things don't line up the temptation is to move forward, but we really dug into the weeds to figure out what was going on and that's when we realized that the genes were communicating and working together and that's what's really new," said Pozniak.

"If we had given up after the first set of experiments, we never would have concluded that two genes coming together was needed for resistance. It's a great science story."

Identifying complex gene interactions that offer greater resistance, like the ones published in this most recent paper, are crucial in the continued battle against crop disease. Because of the genes' odd behavior, Klymiuk developed a DNA test to ensure the pair of genes are present in new plants. With this DNA test, these genes can be used routinely in the breeding program.

These discoveries allow the CDC to add robust tools to their genetic tool kit, helping to produce stronger and more resilient varieties of wheat for many years to come.

"The interconnectivity of research and breeding lets us keep an eye on the prize and develop the most productive varieties for farmers. This project also really helps us understand and appreciate the complexity of plant biology. Plants really need to adapt, and they do it in cool and interesting ways," said Pozniak.