Developing resistant wheat varieties

A new $5 million grant to wheat breeders could shorten the time between the outbreak of diseases and the development of resistant wheat varieties, said the Texas Agricultural Experiment Station state wheat breeder.

The research supported by the grant is called "˜marker assisted selection,' said Dr Jackie Rudd, Experiment Station state wheat breeder in Amarillo. Marker assisted selection takes genome research from the laboratory to the field via new disease-resistant, high quality varieties.

Rust problems alone reduced the grain yield of the Texas wheat crop by about 20 percent last year, Rudd said. This cooperative technology will not only help to combat that, but will help produce better grain products and help maintain the international competitiveness of US wheat.

A traditional breeding program evaluates genetic variability of a selected line of wheat by planting it over several years in many locations, and then determining if it has the resistance needed, Rudd said.

"It's a 'what you see is not what you get' situation," he said. "This new grant will help us look at the DNA of a wheat plant to determine what genes it has before it is planted, rather than wait to see if it is expressed in the field. It's a way of increasing our overall efficiency."

Texas' Experiment Station wheat-breeding program has been working to identify the molecular markers for leaf rust resistance and greenbug resistance for the past five years, Rudd said.

Molecular markers can be a piece of DNA, near a gene or within a gene, that signals the presence of a useful trait such as disease resistance.

In traditional breeding, if 1000 rows of wheat lines are planted, about half will be thrown out due to stripe or leaf rust problems, he said.

"If we can look at the DNA before planting those rows and determine they have the effective resistance genes, we can be more selective in our planting," Rudd said.

Leaf rust resistance, for instance, is hard to maintain because the pathogen changes, sometimes as often as every few years, he said. A more durable resistance can be obtained by combining genes that may only have partial resistance individually. This can be done much more efficiently using molecular markers.

The genetic information will be stored in national databases and seed stocks deposited in USDA's Small Grain Collection, providing long-term public access of genetic information and resources for the wheat breeders and researchers nationwide, USDA officials said.

Wheat is one of the few major crops where public sector researchers are largely responsible for providing new varieties for farmers, Rudd said. The grant will bring these public wheat-breeding programs into a community, making the most efficient use of the public money.