Researchers have discovered potential genetic resistance in field peas to Fusarium wilt, a fungal disease that causes premature plant death. The Agriculture and Agri-Food Canada (AAFC) scientists identified the material by scanning the genetic 'bank' of field pea germplasm and cultivars, and will now use the most promising material to develop wilt resistant pea cultivars adapted for Prairie conditions.

The Fusarium wilt (Fusarium oxysporum f.sp. pisi) pathogen is among the major diseases threatening field pea production on the Prairies. A soil-borne fungus, it causes yield losses and severe infections that can completely spoil a pea crop. Fusarium wilt occurs wherever peas are grown and it can survive in fields for up to ten years.

"Breeding for resistance to Fusarium wilt in field peas has had little success due to lack of information about the makeup of the pathogen and because the availability of resistance in existing breeding material has not been determined," says Dr. Bob Conner, pathologist at the AAFC Cereal Research Centre in Morden (Morden Research Station), Man.

Conner led the project along with colleagues Dr. Allen Xue, plant pathologist at AAFC Eastern Cereal and Oilseed Research Centre in Ottawa and Dr. Ron Knox, biotechnologist at AAFC Semiarid Prairie Agricultural Research Centre in Swift Current. The scientists recently completed a three-year study on Fusarium wilt and resistance inherent in various pea cultivars. The research was supported, in part, by the Western Grains Research Foundation (WGRF) Endowment Fund.

Previous U.S. research indicated the existence of four races of the Fusarium wilt pathogen. To determine what races are present in western Canadian pea fields, a survey was performed where infected plant material was collected from more than 100 sites in Manitoba, Saskatchewan and Alberta over three growing seasons (1999 to 2001).

"Three out of four known races of Fusarium wilt were identified in the collected plant material," says Conner. "Two of these races are highly virulent, including the race that was found to be most widespread."

To determine the availability of Fusarium wilt resistant breeding material, the research team evaluated the symptoms of 117 field pea varieties that had been exposed to the disease.

"Cultivars Radley and Princess were found to be resistant to the two most virulent Fusarium wilt races identified in the field survey and 39 percent of the cultivars were resistant to the least virulent race," says Conner. "Remaining cultivars, nearly 60 percent, were found to be susceptible to all pathogen races."

Breeders at the Morden Research Station will now include the most promising resistant field pea cultivars in the breeding program in order to transfer the wilt resistance genes into agronomically superior pea varieties, he says.

"We actually detected resistance in some of the advanced breeding lines from the breeding program," says Conner. "These lines have to be put through final screening and evaluation, but should then become available on the market."

Using new screening procedures, labour and time involved with screening is greatly cut, he adds. The new screening procedures have proved efficient and reliable and are becoming standard protocol for these types of laboratory tests.

In an effort to further enhance breeding efficiency, the researchers also identified molecular markers for the resistance gene associated with the most common Fusarium wilt race.

Eight significant markers showed promise as selection tools but some modifications are still needed to make them useful to breeders, he says.

"The ultimate goal is to provide producers with new field pea varieties that have a package of resistance genes for Fusarium wilt and other diseases," says Conner. "This would provide the best option for long-term pathogen control and increase the appeal of peas as a Prairie crop."