The Effect of Crop-Weed Gene Flow on the Competitive Ability of Weedy Sunflower

The Effect of Crop-Weed Gene Flow on the Competitive Ability of Weedy Sunflower

Summary

This study compares the competitive ability of crop-weed hybrids under agricultural conditions to elucidate environmental effects of crop-weed gene flow. Weedy sunflower populations from nine locations were crossed with conventional and herbicide resistant sunflower crop lines to create a diversity of crop-weed hybrids. These hybrids and their weed counterparts were grown with and without wheat competition. The wheat treatment had an effect on the early growth and seed production of all of the sunflowers. However, the differential effect on weedy and crop-weed hybrid plants, and the differences between herbicide resistant and susceptible hybrids, will only be discerned with future analysis.

Objectives/Performance Targets

1. To quantify the competitive abilities of sunflower weeds and crop-weed hybrids under competition with wheat.
2. To investigate possible fitness differences between herbicide resistant and herbicide susceptible crop-weed hybrids.

Accomplishments/Milestones

The first major accomplishment of this project was to create the genetic materials needed for the experiments. All of the crosses were done by hand in the greenhouse and the field by myself and a student worker in the summer of 2002. The second major achievement was to carry out the experiment in the field in 2003. We had a successful field season without much lost to insects, disease or drought. The most time consuming data collected relates to the estimation of total number of seeds produced per plant. We have finished counting the seed samples and are entering the data from the entire experiment presently. Data analysis will commence as soon as the data sets are ready. At that point I will begin to explore the differences in effects of wheat competition on weeds and crop-weed hybrids (objective 1) and among herbicide resistant and herbicide susceptible hybrids (objective 2).

Impacts and Contributions/Outcomes

Gene flow from crop fields into weedy or wild plant populations is of environmental concern. This hybridization has the potential to cause increased invasibility in weed populations. The United States is the center of origin for sunflowers, which makes gene flow an even more pressing concern. This is especially true as crop varieties are being developed that have novel traits, such as herbicide resistance or pest resistance.

To date I have discussed this research and its implications with colleagues in the University of Minnesota, including a presentation to the Center for Community Genetics. I have also discussed the research with industry representatives interested in introducing sunflower crops with novel traits. I do all of this to increase awareness of potentially environmentally problematic effects of gene flow. The representatives have solicited my opinions regarding stewardship guidelines for these crops.

Additionally, I have employed nine students on this project. Through the experience, their awareness about the gene flow issue has been increased.

As we clarify the differences between normal weeds and crop-weed hybrids in their competitive ability, we will be able to contribute to the discussion about how to best regulate crops with novel traits to decrease the possibility of creating more weed problems for all farmers.

Collaborators: