Wheat streak mosaic resistance bred into several wheat varieties might be negated by the producer practice in the High Plains of planting wheat early and using it for both winter forage for cattle and grain, according to a Texas AgriLife Research scientist.

Dr. Charlie Rush, AgriLife Research plant pathologist in Amarillo, began a study in December that he “started out of necessity” after working for several years on the wheat streak mosaic virus.

While several varieties of wheat, such as Mace and Ron L, have resistance to the virus bred into them, there has been a problem with that genetic resistance breaking down in temperatures above 75 degrees, Rush said.

“That is terrible for those who plant in the Texas Panhandle for dual purpose,” he said. “The wheat is planted early when temperatures are very high and it’s too hot for genetic resistance to be effective. In our study, we want to see if the plant is able to grow out of it once temperatures cool down to where the genetic resistance should be effective.

“It’s really important to understand how the germplasm responds to the natural temperature fluctuations during the growing season,” Rush said. “Since we know most of the farmers in this area plant when it is too hot for the resistance, we need to know what happens once the temperatures cool down.”

Jacob Price, a research associate on Rush’s team, is running diagnostics for the virus and quantifying the infection of the plants. He is also looking at the virus quantity in the wheat curl mites, which are the vector of the disease, to see if that is altered among the varieties.

Wheat streak mosaic virus is the most prevalent disease in the southwestern wheat producing region of the U.S., Price said. Early diagnostics have shown that wheat curl mites have the potential to build high populations very quickly. When populations explode, wheat streak can spread to epidemic proportions in a short time, causing devastating losses throughout the wheat growing region.