Barley producers in the United States face an unpleasant challenge this year with the arrival of stripe rust. It is a fungus that has already done enormous damage in South America, where it has wiped out barley crops used for food, as well as for feed and beer.
But the fungus is going to be out of luck in the Pacific Northwest, thanks to gene mapping—and strong collaboration between ICARDA's Latin American Regional Program and Oregon State University (OSU).
Together, ICARDA and OSU researchers have succeeded in producing resistant varieties that will be ready for yield testing in 1996. They have done it by identifying the disease-resistant material in their germplasm, allowing them to breed new resistant lines far more quickly than with the traditional plant breeding methods.
The story began ten years ago. Dr Hugo Vivar is the Barley Breeder and Latin American program coordinator for ICARDA—the International Center for Agricultural Research in the Dry Areas—which is based in Aleppo, Syria, and has a world-wide mandate for barley improvement.
Over the last decade, Dr Vivar, working out of ICARDA’s sister center, CIMMYT*, near Mexico City, has developed an impressive armoury of barley germplasm which is resistant to biotic stresses—that is, pests and diseases, such as yellow rust. He then worked with national research programs to exploit this germplasm. This led to the release of tough, productive varieties such as Calicuchima and Shyri in South America.
“I’m particularly excited about Shyri at the moment,” says Dr Vivar. “The latest crosses being tested in Ecuador right now are giving very good results—five times the national yield average. That doesn’t necessarily give Ecuadorean farmers five times the yield. As any crop breeder or farmer will tell you, it depends on seed production and agronomic practices. But I think a doubling of barley production is realistic.”
These are no ordinary crosses, however. Also ten years ago, Dr Patrick Hayes, Associate Professor of Crop and Soil Science at Oregon State University, Corvallis, USA, started to work with the double-haploid technique. This works by isolating one-half of the chromosomes and then doubling them with the chemical colchicine, producing a plant that is homozygous—that is, which breeds true to its characteristics in every generation. This permits much faster production of true breeding lines. Four years ago, the two men teamed up to try and characterize and manipulate multiple disease-resistant germplasm.
Now they have used molecular markers to speed up the identification of stripe-rust resistant lines. Of 134 double-haploid lines of Oregon-grown barley, 13 were found to have high resistance to stripe rust. The work took two years, and yield-testing of these disease-resistant lines will start next year. It is a tremendous improvement on earlier techniques.
The strategy has been for Dr Hayes’ laboratory to develop doubled-haploid mapping populations from crosses of Dr Vivar’s resistant germplasm with genotypes adapted to the Pacific Northwest of the USA. Dr Vivar’s team then conducts extensive tests for disease reaction in central Mexico, while Dr Hayes’ group does molecular marker analysis in order to map the genes and find the sources of resistance.
“It took 20 years for barley stripe rust to move from Colombia to Oregon,” says Dr Hayes. “It can take almost that long to go from making a cross to large-scale commercial production of the resistant barley variety. But barley growers in the Pacific Northwest aren’t going to be waiting that long.
“What this means is that plant breeders will be one step ahead of pests and diseases as they move around the world.” The benefits of this for farmers should be important in the US, but in the developing world it is absolutely crucial. There are real implications for food security.
Barley is also a tremendously important crop in the Middle East and North Africa, and ICARDA is working with national programs there to stabilize yields by exploiting local sources of resistance—in Ethiopia, for example—and by collaborating with farmers on crop trials.
“Agricultural research isn’t going to remove all the risk from farming just yet!” says Dr Vivar. “And if it was, plant breeders would not be able to do it on their own. Still, we are protecting the poor. Barley is mainly used as cattle feed, but is also a staple part of the diet in the mountains of Bolivia, Peru and Ecuador—I am Ecuadorean myself, by the way.
“But we are all in the same business—Ecuadoreans, Ethiopians, North Americans. That business is farming. And the way Pat and I see it, anything which helps farmers in both Oregon and Ecuador can’t be bad.”