Pollen-Mediated Gene Flow in Commercial Fields of Spring Wheat in Western Canada

Crop intraspecific pollen-mediated gene flow (PMGF) can be scale dependent. In 2004-the first year imidazolinone (IMI)-resistant spring wheat (Triticum aestivum L.) was commercially available-a study was conducted in western Canada to examine PMGF in commercial fields. At each of two sites located 4 km apart in the semiarid grassland region of Saskatchewan, PMGF was measured from a 16-ha (400 x 400 m) field of IMI-resistant wheat (cultivar CDC Imagine) to an adjacent field of conventional (non-IMI-resistant) wheat (cultivar AC Barrie) with the same dimensions. Wheat grain samples of AC Barrie were collected at varying distances to 400 m along five equally-spaced transects oriented perpendicular to the common border with CDC Imagine. A total of 2000 seedlings per sample were screened for resistance to imazamox at 200 mu M in a 7-d soilless bioassay. Putative resistant hybrids were confirmed by polymerase chain reaction (PCR) analysis. Averaged across transects and sites, PMGF was 0.2% at the common border and declined exponentially with increasing distance; the maximum distance that PMGF was detected was 80 m from the donor field. Higher levels of PMGF were generally observed in this study compared with that of previous studies in western Canada. Results of this study provide a more complete assessment of PMGF in this crop under western Canadian climatic conditions. Together with previous studies, frequency and distance of PMGF can guide grower stewardship practices for identify preservation in wheat cultivars possessing different traits.