The miracles of science™

Select Industry


DuPont Biotechnology website

Gene Flow FAQs

Please select a question from the list below to jump to the answer.


Gene Flow - Crop to Crop


Gene Flow - Crop to Wild





Can cross-pollination between different crops occur?

No. Many factors naturally limit cross-pollination between different varieties, such as their tendency to self-pollinate and the limited length of time pollen is viable. Growers can further enhance these limitations by growing different varieties of a crop at recommended distances from each other and using border rows in those crops that have a greater capacity for cross-pollination, such as corn and canola.

What is the likelihood cross-pollination of biotech and non-biotech varieties will occur?

The answer varies with the crop and environmental conditions. If non-biotech varieties are growing in proximity to biotech varieties, then a number of crop-related factors influence the likelihood of cross-pollination, such as pollen size, which affects the distance pollen travels in wind-pollinated crops; pollen competition, which is a function of the relative amount of pollen the two varieties produce; and the mode of pollination - wind, insect or both. The relevant environmental factors include wind speed and direction, presence of barriers between fields, percent relative humidity and temperature.

Back to Top

If cross-pollination occurs, are negative agricultural or environmental impacts inevitable?

No. Specific impacts depend upon the crop, the function of the biotech genetic material and the commercial interests of the grower. Looking at the experience gained from growing conventionally bred crops for many decades, it seems that rarely, if ever, will cross-pollination of biotech and non-biotech crops have negative agricultural impacts. In a few instances, herbicide tolerance genes in conventional crops have made weed control more difficult, but manageable, in some crop rotation systems. On the other hand, there are no reports of insect resistance and disease resistance genes in conventionally bred crops causing problems for farmers. Trace amounts of cross-pollination between biotech and non-biotech crops could have negative economic impacts if regulatory agencies establish thresholds for genetic purity of non-biotech grain that exceed long-established standards.

Can herbicide tolerant genes move from crops derived through biotechnology into other crops and landraces and create invasive, persistent crops?

Herbicide tolerant genes can move from biotech to non-biotech crops and to some landraces, but this does not necessarily lead to the creation of "supercrops" with weed-like traits that make them difficult to control. Our experience with conventionally bred crops shows that if crops with invasive tendencies acquire resistance to certain herbicides either by cross-pollination or through natural evolutionary forces, these crops can be controlled with other herbicides on the market. In addition, only a handful of crops, such as canola, rice and sorghum, have potentially weedy traits in agricultural systems or persistence in natural environments. Modern-day corn and soybeans cannot persist outside of cultivated, agricultural settings.

Back to Top

Does pollination of a non-biotech crop by a biotech variety affect the safety of food derived from the non-biotech crop?

No. Scientists and regulatory authorities all over the world have deemed food derived through biotechnology to be as safe as other food on the market and have repeatedly stated that there is no risk in consuming biotech genetic material.

What is adventitious presence?

Adventitious presence is the presence of small amounts of genetic material or whole seeds from another variety, crop or weed in a seed or grain shipment. Virtually all seed and commercial grain shipments contain some adventitious material even though seed companies, farmers and the grain trade take many steps to minimize it. Recognizing its inevitability, national and international regulation of the seed and grain industries has taken adventitious presence into account for years by establishing thresholds for purity levels in seed shipments and that are slightly less than 100%.

Back to Top

What steps does DuPont take to minimize adventitious presence in seed products?

DuPont invests significant time and resources to maintain the highest possible level of seed variety purity so that our customers will enjoy the full genetic potential of a specific variety, whether we developed it with conventional breeding or biotechnology.

During seed production and harvesting, we meet or exceed the requirements of international, national and state regulatory authorities by using many strategies to prevent cross-pollination and seed mixing such as using required isolation distances between fields; planting border rows of a different variety that is not harvested for seed; staggering the planting dates of adjacent fields so that pollen shedding and receptivity are not in sync; and carefully cleaning the planting, harvesting, storage and conditioning equipment after each use. In addition, field inspectors monitor seed field operations to help ensure purity. Finally, we have a state-of-the-art genetic purity testing program and a detailed product identification and tracking system that is supported by ISO9000 and a complex information management system.

Can cross-pollination occur between crops derived through biotechnology and wild, native plants?

Cross-pollination can occur if the crop and wild plant are very closely related, whether the crop is derived through conventional breeding or biotechnology. However, many factors limit cross-pollination between crops and their wild relatives, such as the proximity of the crop and wild relative; compatibility of their reproductive cycles; tendency to self-fertilize; and the length of time pollen is viable.
Back to Top

If pollen from a crop derived through biotechnology is carried to a wild relative, are the genes automatically transferred to the wild relative?

 No. A number of factors determine whether pollen transfer leads to gene transfer, the most important being the degree of relatedness between the crop and wild relative. Gene transfer depends upon crop pollen fertilizing the egg of the wild plant. Cross-fertilization must lead to the production of hybrid seeds that are fertile and produce offspring for gene flow to occur. These are key examples of the barriers that nature provides to minimize the potential for interbreeding between different plants.

What is the likelihood the new genes in crops derived through biotechnology will be transferred to wild plants?

 The answer to this question varies with the crop, the location where it is grown and the wild plant. The one general statement that is true for all crops is that genes can potentially be transferred only in those locations where the crop has wild relatives. Therefore, to assess the likelihood of gene flow from any crop to its wild relative, first determine whether the crop is growing in a geographic region that contains wild relatives. If not, the likelihood of gene transfer is zero. If wild relatives are growing in close proximity to the crop, then a number of factors influence the likelihood of gene flow, such as the distance viable crop pollen can travel, the amount of crop pollen produced, the mode of pollination, and the number of wild plants in proximity to the crop.
Back to Top

If gene flow occurs, are negative ecological impacts inevitable?

 Looking at the experience gained from growing conventionally bred crops for many decades, it seems that very rarely, if ever, will gene flow from a crop to a wild relative have a significant ecological impact. Gene flow from a conventional crop to a wild, weedy relative has been documented. In a few instances, the new genes have had a negative impact on crop management because controlling the hybrid weed growing in fields of the conventional, related crop became more difficult. However, adverse effects on agricultural systems should be distinguished from negative impacts on natural ecosystems. Past gene flow from conventional crops to wild, native plants appears not to have had a noticeable impact on natural ecosystems. In order to have negative environmental effects, the gene must become widespread in the wild plant population and give the wild plants possessing the crop genes a competitive advantage over those without the crop genes.

Can herbicide tolerant genes move from crops derived through biotechnology into weeds and create "superweeds?"

 Herbicide tolerant genes can move from some crops to certain weedy relatives in some locations, but this will not necessarily lead to the creation of superweeds. Weedy relatives might acquire tolerance to a specific herbicide, but if the weedy relative is not treated with that herbicide, then having the new gene offers no competitive advantage. Even though the weed may no longer be susceptible to that herbicide, it can be controlled with a number of other herbicides.
Back to Top

Will gene flow from crops derived through biotechnology decrease the genetic diversity of wild plant species?

 Because fertilization of wild plants with crop pollen is relatively rare when compared to fertilization of a wild plant with wild plant pollen, gene flow from crops to wild plants will rarely, if ever, have a significant impact on the genetic diversity of wild plants.

Do regulatory agencies assess the potential for gene flow and its consequences during their review of crops derived through biotechnology?

 Yes. In the U.S., assessing the likelihood and impacts of gene flow is a component of the regulatory review process at both the U.S. Department of Agriculture (USDA) and the Environmental Protection Agency (EPA). Regulatory bodies in other countries also require the submission of data on gene flow probability and its potential impacts.

Back to top