Soybean Research

Evaluation and testing selected plant introductions from the USDA for soybean rust resistance
Dr. Istvan Rajcan, University of Guelph; Albert Tenuta, OMAFRA

Currently there is no effective resistance to Asian soybean rust (P. pachyrhizi) in commercially available North American soybean varieties. The development of varieties incorporating a novel set of resistance genes against a new disease threat such as soybean rust can be difficult, time consuming and requires considerable commitment. The purpose of this multi-year project is to not only evaluate potential sources of resistance (PI lines) to Asian soybean rust but to develop soybean rust resistant varieties for the Ontario and Canadian market. One of the benefits of working with the US in an integrated North American soybean rust approach has been access to germplasm and resources which would otherwise be unavailable.

This cooperation has provided Ontario public breeding programs at Agriculture and Agri-Food Canada (AAFC) in Harrow and Ottawa as well as the University of Guelph programs in Guelph and Ridgetown with access to the USDA soybean rust nursery and screening trials in Quincy, Florida. The ability to test Ontario soybean lines in the southern US under significant and consistent soybean rust disease pressure allows us to speed variety development.

This location was utilized first in 2007 and then again in 2008. By using the Quincy nursery, we were able to confirm and progress with Ontario breeding lines derived from crosses between Ontario adapted lines such as OAC Kent with soybean rust resistant plant introductions. Of the 296 lines sent to Florida for screening in 2008, 14 percent were resistant (rating 1 or 2), with 13 having a rating of 1 (“no rust”). Seed of resistant lines was distributed to the Canadian public soy breeder collaborators of this project and are available to other breeders on request.

The screening efforts also demonstrated one Ontario line with partial (rate-reducing) resistance or tolerance. With “rate-reducing resistance” the development of the disease is slowed and the lesions produce fewer spores. Varieties that express the “tolerant trait” have been demonstrated to have less yield loss due to soybean rust.