Sea wheatgrass as new source of wheat virus resistance?

Associate Professor Wanlong Li of the Department of Biology and Microbiology leads the nearly $250,000 project, which is part of NIFA's Agriculture and Food Research Initiative to improve plant health and production. Professor Marie Langham, a virologist, and Assistant Professor Qin Ma, a bioinformatician, from the Department of Agronomy, Horticulture and Plant Science are also part of the SDSU research team. They will collaborate with Cereals Crop Research Geneticist Steven Xu from the USDA Agricultural Research Service in Fargo, North Dakota.

"Historically in wheat breeding, we have a lot of very important genes transfer red from alien species or relatives to wheat varieties," he said. For instance, resistance to leaf rust, stem rust and yellow rust, as well as powdery mildew, came from rye.

The idea for the sea wheatgrass research began in 2014 when Li's plants in the greenhouse became infected with wheat streak mosaic virus. Only two lines survived -- sea wheatgrass and a wheat/sea wheatgrass hybrid. Experiments in summer 2016 confirmed that these two lines are resistant to the virus, but the parent wheat plant is not.

Additionally, the virus resistance is not temperature sensitive. "The current resistant gene used in wheat breaks down at temperatures above 64.4 degrees Fahrenheit, but this one is still resistant up to 82 degrees Fahrenheit," Li explained.

Further testing showed that the hybrid and sea wheatgrass tolerate excess water. Waterlogging is a problem for wheat growers in states such as Arkansas and Louisiana, as well as countries like Bangladesh, Li explained.

"We want to figure out genetically what makes this resistance and transfer those genes to bread wheat," he said. The researchers have sequenced the sea wheatgrass genome and will compare it with wheat to identify the genes responsible for resistance. They will then develop molecular markers for those genes.

Sea wheatgrass also has a solid stem, making it resistant to the sawfly, a pest that lays its eggs in the hollow wheat stem and makes the wheat break, noted Li. The sawfly is a serious problem in spring wheat growing areas in Montana, North Dakota and parts of South Dakota, and spiked in the winter wheat growing areas in Colorado and the Nebraska Panhandle in recent years as well.

"We have to do the selection and reduce the alien chromosome size and transfer a small fragment to the wheat," he said. "Sea wheatgrass chromosomes do not want to pair with wheat, so we must continue to back cross and use chromosome engineering to transfer the fragments to wheat -- that takes time."