Oregon State University soft white winter wheat variety Kaseberg did not have a key resistance gene to the disease stripe rust after all, a USDA plant pathologist says.
OSU researchers found stripe rust on Kaseberg in two commercial fields this year. The variety was thought to have a gene with complete resistance to the disease.
Researchers were concerned about the possibility a new strain of stripe rust capable of overcoming a key resistance gene.
People should be aware Kaseberg is likely more susceptible than originally thought, said Mike Flowers, OSU Extension cereal specialist.
“Particularly on the west side here, everybody has got to walk their fields no matter what variety it is, just to see what’s out there and make applications as necessary,” he said.
Kaseberg growers in western Oregon and western Washington, where stripe rust is common because the weather is wetter and warmer, should spray fungicide at the time of herbicide application if they see rust in their fields, said Xianming Chen, USDA Agricultural Research Service plant pathologist in Pullman, Wash.
Kaseberg still has good high temperature, adult plant resistance for stripe rust from its parent wheat varieties, Chen said.
In the eastern Pacific Northwest, farmers generally do not need to spray unless they see rust because stripe rust pressure is at the lowest level since the year 2000, Chen said.
Temperatures in the eastern region were favorable for stripe rust in recent weeks, but there is no or very low inoculum, Chen said.
“Survival after winter is very low,” he said. “They may not need to use fungicide at all this year.”
Chen said breeders probably used a molecular marker to interpret the presence of the resistance gene.
Flowers says Chen’s finding indicates the molecular marker researchers use is incorrectly identifying the resistance gene.
YR5 and YR15 are the two genes that primarily provide stripe rust resistance in wheat germplasm throughout the region.
“It’s good and bad,” Flowers said. “It’s good news that potentially we don’t have a new race of rust that’s taking out the YR5 gene.”
The finding is an indicator that molecular markers aren’t as accurate as most are led to believe, Flowers said.
“Now if you’re looking at a variety that says it has YR5 in it, you may not because the marker that they use to track it isn’t indicative of whether it really has the gene or not,” he said.
No race of stripe rust in the United States has yet attacked YR5, according to Chen.