Scientists find resistance gene against Ug99 wheat stem rust pathogen

The world’s food supply got a little more plentiful thanks to a scientific breakthrough with the wheat stem rust pathogen, according to a report at ScienceDaily (here).

Eduard Akhunov, associate professor of plant pathology at Kansas State University, and his colleague, Jorge Dubcovsky from the University of California-Davis, led a research project that identified a gene that gives wheat plants resistance to a deadly race of the wheat stem rust pathogen called Ug99.

The discovery may help scientists develop new wheat varieties and strategies that protect the world’s food crops against the wheat stem rust pathogen that is spreading from Africa to the breadbaskets of Asia and can cause significant crop losses.

The project was funded by the US Department of Agriculture and Borlaug Global Rust Initiative and the study, “Identification of Wheat Gene Sr35 that Confers Resistance to Ug99 Stem Rust Race Group,” appears in the journal Science.

It identifies the stem rust resistance gene named Sr35, and appears alongside a study from an Australian group that identifies another effective resistance gene called Sr33.

“This gene, Sr35, functions as a key component of plants’ immune system,” Akhunov said. “It recognizes the invading pathogen and triggers a response in the plant to fight the disease.”

ScienceDaily explains that wheat stem rust is caused by a fungal pathogen.

According to Akhunov, since the 1950s wheat breeders have been able to develop wheat varieties that are largely resistant to this pathogen but the emergence of strain Ug99 in Uganda in 1999 devastated crops and has spread to Kenya, Ethiopia, Sudan and Yemen.

“Until that point, wheat breeders had two or three genes that were so efficient against stem rust for decades that this disease wasn’t the biggest concern,” Akhunov said. “However, the discovery of the Ug99 race of pathogen showed that changes in the virulence of existing pathogen races can become a huge problem.”

Researchers spent nearly four years trying to identify the location of the Sr35 gene in the wheat genome, which contains nearly two times more genetic information than the human genome.

Now that the resistance gene has been found, Akhunov and his colleagues are looking at what proteins are transferred by the fungus into the wheat plants and recognised by the protein encoded by the Sr35 gene. This will help researchers to better understand the molecular mechanisms behind infection and develop new approaches for controlling this devastating pathogen.

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