An international team of researchers, led by a University of California, Davis, plant scientist, has identified a gene that should protect commercially important wheat varieties from stripe rust, a disease that causes severe crop losses in the United States and other wheat-growing regions.

The research findings have significant implications for consumers around the world, who rely on wheat for about 20 percent of their calories. Findings of the study are reported in the Feb. 19 issue of Science Express, the online version of the journal Science.

“We anticipate that introduction of the Yr36 gene into wheat varieties used for making pasta and bread will have broad impact on improving resistance to the fungus that causes stripe rust,” said Professor Jorge Dubcovsky, a wheat breeder and geneticist at UC Davis.

Stripe rust, which affects millions of acres of wheat, is caused by the Puccinia striiformis fungus. Virulent forms of the fungus have appeared in the past decade, overcoming known disease-resistance genes in wheat and causing large yield losses.

The fungus and resulting stripe rust are spread by the wind and are most damaging to crops grown in areas with mild winters and wet falls and springs. The disease first appears as rows of yellow-orange spore clusters on wheat leaves.

The newly identified Yr36 resistance gene was first discovered in wild emmer wheat, a low-yielding wheat that grows wild in Israel. The gene is absent from modern wheat varieties used for making bread and pasta.

The researchers identified Yr36 using positional cloning, a technique which enabled them to pinpoint the gene’s location on the chromosome and identify its DNA sequence and predicted protein. Publication of the gene sequence will give breeders the ability to use sequence-based DNA markers to incorporate Yr36 into new wheat varieties.

The gene, which has been transferred into a handful of domesticated pasta and bread wheat varieties, provides only partial resistance to stripe rust. However, when combined with other partial resistance genes, such as the Yr18 gene, it provides adequate levels of protection.

“Historically, broad-resistance genes have been more durable than those that confer more complete resistance, but to a much smaller subgroup of races of disease-causing pathogens,” Dubcovsky said. “In addition, the Yr36 gene protects wheat against all known strains of stripe rust, making it an effective tool for wheat breeders and growers.

Dubcovsky noted that wheat plants carrying the Yr36 gene in California field trials, initiated in 2003, continue to demonstrate resistance to the many types of stripe rust found in the state. The plants produce significant yield increases when the disease is present.

This research was funded by the U.S. Department of Agriculture’s Cooperative State Research, Education and Extension Service, and the U.S.-Israel Binational Agricultural Research and Development Fund.

Other UC Davis researchers working on the study were Lynn Epstein; Daolin Fu; Assaf Distelfeld; and Cristobal Uauy, now at Norwich BioScience Institutes, England. Other members of the research team were Hanan Sela of the University of Haifa, Israel; Ann Blechl of the U.S. Department of Agriculture’s Agricultural Research Service in Albany, Calif; and Xianming Chen of the USDA Agricultural Research Service at Washington State University.

About UC Davis

For 100 years, UC Davis has engaged in teaching, research and public service that matter to California and transform the world. Located close to the state capital, UC Davis has 31,000 students, an annual research budget that exceeds $500 million, a comprehensive health system and 13 specialized research centers. The university offers interdisciplinary graduate study and more than 100 undergraduate majors in four colleges — Agricultural and Environmental Sciences, Biological Sciences, Engineering, and Letters and Science — and advanced degrees from five professional schools: Education, Law, Management, Medicine, and Veterinary Medicine. The UC Davis School of Medicine and UC Davis Medical Center are located on the Sacramento campus near downtown.