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ARS Home » Southeast Area » Mississippi State, Mississippi » Crop Science Research Laboratory » Corn Host Plant Resistance Research » Research » Publications at this Location » Publication #208732
Title: Adventitious presence of herbicide resistant wheat in certified and farm-saved seed lots

Author
item GAINES, TODD - COLORADO STATE UNIVERSITY
item PRESTON, CHRIS - UNIVERSITY ADELAIDE
item BYRNE, PAT - COLORADO STATE UNIVERSITY
item Henry, William
item WESTRA, PHILIP - COLORADO STATE UNIVERSITY

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2007
Publication Date: 3/1/2007
Citation: Gaines, T., Preston, C., Byrne, P., Henry, W.B., Westra, P. 2007. Adventitious presence of herbicide resistant wheat in certified and farm-saved seed lots. Crop Science. 47:749-754.

Interpretive Summary: Varietal purity is an important subject to both consumers and producers of wheat. This study was conducted to determine how often wheat seed contamination occurs if herbicide resistant wheat is included in a farmer’s seed production operation. Because one variety of wheat is resistant to herbicides, it was possible to measure seed contamination by collecting seed from the non-resistant wheat, applying herbicide to the seeds in a dilute solution then measuring the number of plants that survived the application and germinate. The objectives of the study were to compare wheat seed purity based upon the type of seed producer and the history of herbicide resistant wheat use. Producers in the study were either certified seed growers or farm-saved seed growers. These designations represent varying levels of management practices to ensure seed purity. It was noted whether or not these farmers had ever grown or were currently growing the herbicide resistant wheat variety. Levels of seed contamination ranged from 0% to 11.28%. One certified sample and three farm-saved samples exceeded the 0.1% threshold for off-types in certified wheat seed. Based on grower interviews, higher levels of adventitious seed presence were associated with volunteer plants from previous crops of the resistant variety and mechanical mixture during harvesting. Production practices for certified seed address these factors and may need to be strengthened if more stringent purity criteria are adopted. In summary, this information is important for risk assessment and policy development for potential commercial release of transgenic wheat varieties.

Technical Abstract: Varietal purity in wheat (Triticum aestivum L.) seed production is necessary for agronomic uniformity and to enable potential market segregation. We conducted a survey of certified and farm-saved seed samples using a non-transgenic imidazolinone resistant (IR) wheat variety in 2004 and 2005 in eastern Colorado. The objective was to compare varietal purity based on type of seed producer and IR wheat history. Ninety-two samples of non-IR varieties were taken from certified and farm-saved seed growers, who either produced or had never produced IR wheat. Adventitious IR seeds were detected using a seed soaking technique in samples from each producer type and each IR production history. Levels of IR seed ranged from 0% to 11.28%. One certified sample and three farm-saved samples exceeded the 0.1% threshold for off-types in certified wheat seed. Using a two-factor analysis, farm-saved production class and positive IR history increased the estimated proportion of adventitious seed. Based on grower interviews, higher levels of adventitious seed presence were associated with volunteer plants from previous crops of the resistant variety and mechanical mixture during harvesting. Production practices for certified seed address these factors and may need to be strengthened if more stringent purity criteria are adopted. This information is important for risk assessment and policy development for potential commercial release of transgenic wheat varieties.