Apr 6, 2011

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Outcrossing wheat: Field trial

Outcrossing in wheat over long distances under field conditions

Crop Barley /wheat
Year 2007
Country Canada Canada
Execution Department of Plant Sciences and Crop Development Centre, University of Saskatchewan, Kanada

Experiment

Type of experiment:

Field trial, measuring GMO content Measuring the rate of gene flow in wheat in a two-year large-scale field study (trial years: 2002 and 2003). It is the first trial to investigate gene flow in wheat over long distances (between 300 m and 10 km) under commercial farming conditions.

Experimental design:

The field with the pollen donor wheat was of a commercial scale (33 hectares in 2002 and 20 hectares in 2003). The wheat variety used as the pollen donor contained a marker gene that colours the grains blue. Gene flow from the pollen donor was measured in commercial wheat fields within a radius of ten kilometres. Cross-pollination to this crop could be identified by the blue coloration of the grains.

Experimental procedure:

At maturity, an area of up to two square metres was harvested from each corner of the neighbouring wheat fields: 69 fields in 2002 and 76 in 2003. These fields all had flowering periods that overlapped with that of the pollen donor field. The blue grains were counted and sown in the greenhouse so they could be checked. This enabled ‘false blue’ seeds (e.g. those coloured by disease or weather conditions) to be identified.

Results

  • In 2002 no cases of gene flow were measured beyond a distance of 190 m. At 190 m there was one case of gene flow at a rate of 0.01 %.

  • The trials conducted in 2003 found a total of nine seeds in the recipient fields that could be attributed to gene flow from the central pollen donor field. The distances from the pollen donor field were 500 m, 630 m and 2.75 km. At these sampling points, the rate of gene flow was no more than 0.01 %. No cases of gene flow were found over distances greater than 2.75 km.

  • The average gene flow rate up to 2.75 km from the pollen donor field was found to be less than or equal to 0.01 %.

  • The gene flow rates measured in 2003 represent maximum rates because the humidity levels in this year (70-75 %) and air temperatures (16-20 °C) provided optimum conditions for the viability of the wheat pollen grains. In addition, outcrossing was encouraged by strong, prevailing winds (average 22 km/h).

The authors conclude that pollen-mediated gene flow over long distances does not play a significant role in the potential mixing of GM and conventional wheat.

Documentation: