DISEASE: THE NEW ENEMY
WHIlE MUcH WoRK IS UNDERWAY to enhance crops’ nitrogen use, water efficiency and yields, the rising incidence of diseases such as rust and fusarium head blight mean breeding programs still have to maintain a focus on basic agronomics. Crop scientists fear Ug99 stem rust could wipe out more than 80% of worldwide wheat crops – with statistics like that it is clear that developing new varieties with increased disease resistance should be a top priority.
Breeding for disease resistance is a major focus of public sector research. “The U.S. Department of Agriculture’s Agricultural Research Service supports major efforts in protecting crops from fusarium and rust diseases,” says Kay Simmons, ARS National Program Leader for Plant Genetics and Grain Crops.
ARS manages the U.S. Wheat and Barley Scab Initiative to reduce the occurrence of the diseases and fund coordinated research projects developing resistance to fusarium head blight, also known as scab. Already six universities have released a number of varieties with fusarium resistance with support from the Initiative.
All of these cultivars give farmers the opportunity to use high yielding, scab resistant cultivars. Further, as breeders in the region focus heavily on scab resistance, susceptible lines in the programs are discarded, a method which is widely viewed as one of the most productive things the industry can do to improve overall scab resistance of the varieties available to our growers.
In spite of these breeding successes, challenges remain. According to the Scab Initiative, the biggest breeding challenge lies in combining scab resistance with agronomic superiority and acceptable milling and baking quality, as well as convincing farmers to grow resistant varieties. However, this year’s reports of relatively low levels of FHB despite record rains lead Simmons to suggest the “value of our new varieties in this harvest year.”
However, progress seems a bit further away on Ug99 stem rust. The race is on to develop new wheat varieties that are resistant to Ug99 before it reaches the U.S.
Scientists have identified a mere half-dozen genes that are immediately useful for protecting wheat from Ug99. Incorporating them into crops using conventional breeding techniques is a nine to 12 year process that has only just begun. And that process will have to be repeated for each of the thousands of wheat varieties.
“All the seed needs to change in the next few years,” said Ronnie Coffman, a Plant Breeder who heads the Durable Rust Resistance in Wheat project, in a recent New York Times article. “It’s really an enormous undertaking.”
“You can’t just breed it into one or two major varieties and expect to solve the problem,” added Jim Peterson, a Professor of Wheat Breeding and Genetics at Oregon State University in Corvallis. “You have to reinvent this wheel at almost a local level.”
The challenge has sparked a unique co-operative global response. USDA’s ARS became a founding partner in the Borlaug Global Rust Initiative, in alliance with the International Maize and Wheat Improvement Center, the International Center for Agricultural Research in the Dry Areas, the Food and Agriculture Organization of the United Nations and Cornell University.
“We have several collaborative research projects under way that are feeding critical information into BGRI, and these partnerships are the best way to leverage everybody’s resources to combat Ug99,” explains Simmons
ARS is partnering with CIMMYT and the Kenya Agricultural Research Institute to screen wheat and barley lines from breeders from all over the United States for Ug99 resistance. Kenya has had Ug99 since 2001, so having use of the nursery there provides a way for U.S. breeders to find out which of their new varieties and lines may be able to stand up to the rust without bringing the pathogen into the U.S. and without each wheat- or barley-breeding project trying to start its own nursery overseas. More than 8,000 U.S. lines have been evaluated through this program so far.
“Everybody wins. Not only does the United States benefit from this nursery, but ARS is also sharing all the information from these screenings with the other members of BGRI, and they are sharing their results with us,” notes Simmons.
Research thus far has turned up only a handful of promising resistance genes, which crop breeders like Brett Carver at Oklahoma State University in Stillwater are trying to import into vulnerable strains of wheat. Only the best strains are replanted each year, until the 12-year process results in a single new variety with dozens of valuable traits.
In addition, the Bill and Melinda Gates Foundation recently provided a $26.8 million grant to Cornell University to create the Durable Rust Resistance in Wheat project, which will help bolster Ug99 research. With this grant, Cornell University has brought together 15 partnering institutions from all over the world, including ARS, with the goal of systematically reducing wheat’s vulnerability to rust diseases through an international collaboration.
The big companies are taking notice of Ug99 as well. Syngenta, the Syngenta Foundation for Sustainable Agriculture and the International Maize and Wheat Improvement Center just signed a two-year public-private partnership to rapidly identify and map genetic markers for use in wheat resistance
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