STUDENT INSTRUCTIONS

Figures 3A & 3B

In the early 1990’s, it was believed that hybridization between crops and their wild relatives occurred infrequently, even when plants grew in close proximity (Ellstrand 2001). Figure 3A is from a study in which researchers measured the spontaneous hybridization between wild radish, an important California weed, and cultivated radish (the same species), which is an important California crop. The experimenters attempted to replicate a true-life farmer scenario; they grew the crop as if multiplying commercial seed. They then surrounded the field with strands of wild radish weeds. The researchers harvested the seeds from the weeds and tested for hybrids in the progeny of the weed. In this system, the crop genes were clearly shown to enter natural populations. Then, persistence was tested by comparing the fitness (fruits and flowers) of the hybrids created in the first experiment with their non-hybrid siblings.

Figure 3B also depicts persistence of transgenes in wild populations. It looks at crop sorghum, one of the world’s most important crops, which is highly compatible with and readily hybridizes with Johnsongrass, one of the world’s most damaging weeds. A transgene introduced into crop sorghum could enter Johnsongrass populations because these species can spontaneously hybridize. If this transgene were herbicide resistant, Johnsongrass could become an even more problematic weed.


USDA hearing

Everyone will be assigned a group, each taking on a different role: farmers, environmentalists, or United States Department of Agriculture (USDA) employees. Within your group, study and interpret both figures.

Next, discuss with your group members the stance on crop biotechnology, with respect to weed-crop hybridization, that your role would take. Use information from both figures to support your point of view while explaining why the other side is wrong. Remember to discuss why your role has its bias (what is your motivation, etc.). You will have a maximum of 10 minutes to initially present your case.

The USDA will serve as the panel that the farmers and environmentalists are addressing. In response to each 10-minute presentation, there will be one-minute point and counter point arguments from each side. At the end of the debate, USDA will have 10 minutes to discuss the case in private and then will respond to the farmers and environmentalists’ concerns and thoughts, proposing a brief course of action that should be taken.


Literature cited:

Ellstrand, N. C. 2001. When transgenes wander, should we worry. Plant Physiology 125: 1543-1545.