Estimating Landscape-Level Gene Flow in Wheat and Jointed Goatgrass

Jointed goatgrass (L) and wheat (R)

A major concern with genetically engineered (GE) crops is that the introduced genes will spread via pollen to conventional varieties of that crop or to related wild species. This could potentially result in marketing problems for conventional wheat, or negative environmental effects if the genes spread to wild species. Because GE wheat cultivars may be released within the next few years, knowledge of landscape-level gene movement from GE wheat will be important information for regulatory agencies and for growers. We have undertaken a three-year project to estimate gene flow from landscape-level (i.e., commercial-scale) wheat fields, taking advantage of the 2002 first-time commercial planting of a CLEARFIELD* (imazamox herbicide tolerant) winter wheat variety in Colorado. To fund this work we were recently awarded a grant from USDA’s Biotechnology Risk Assessment Research Grants Program.

Our specific objectives are (1) to evaluate landscape-level crop-to-crop gene flow in wheat, using as a marker trait imazamox herbicide tolerance in the newly released wheat cultivar ‘Above’; (2) to evaluate landscape-level gene flow from ‘Above’ wheat to jointed goatgrass and to wheat x jointed goatgrass hybrids, based on imazamox herbicide tolerance; and (3) to compare gene movement in landscape-level evaluations to gene movement in smaller-scale research plots in similar environments.

In each of three years, we hope to identify 20 locations in eastern Colorado where ‘Above’ is planted next to non-CLEARFIELD* varieties. Heading dates will be monitored for ‘Above’ and the adjacent varieties to verify the likelihood of cross-pollination. At harvest, grain samples will be collected at four distances from the edge of the ‘Above’ field: 0 (or as close as possible), 30, 60, and 120 feet. Wherever possible, seeds of jointed goatgrass will be collected from the same fields and sampling distances as the wheat seed. After threshing, herbicide tolerance of the samples will be evaluated by germinating seeds in an imazamox solution. Surviving seedlings most likely received the herbicide tolerance trait through cross-pollination with ‘Above’. To confirm herbicide tolerance, seedlings that grow in the presence of imazamox will be transplanted into potting mix, grown in the greenhouse to the 3-4 leaf stage, and sprayed with imazamox. Percent imazamox tolerance (and therefore, percent cross-pollination) will be calculated as the number of survivors divided by the total number of germinated seeds.

We appreciate the excellent collaboration we received from growers and extension agents this past season, and hope to expand those collaborations in the coming years.

Pat Byrne and Phil Westra
Departments of Soil & Crop Sciences and Bioagricultural Sciences & Pest Management
Colorado State University