Table of Contents

1. Introduction - Gene Flow from Crops to Wild Relatives
2. Gene Flow to Wild Relatives and DuPont Product Development
3. The Potential Impacts of Gene Flow to Wild Relatives
4. Current DuPont Products and Potential Impacts of Gene Flow
5. Future Steps

» More (FAQs)

Gene flow from a crop to a wild, native plant can occur with any crop, including those derived through biotechnology, as long as the crop and wild plant are very close relatives. The possibility that this gene flow will both occur and impact either the environment or agricultural practices is determined by a wide variety of factors. Generally, gene flow from crops to wild relatives is a rare event.  » More

For gene flow via cross-pollination to occur, viable pollen from the crop must reach the egg of the wild plant before other pollen fertilizes it. Many factors determine the likelihood of this happening:

• proximity of the crop to the wild relative;
• the wild plant's tendency to self-fertilize, which commonly occurs in plants;
• whether corn pollen sheds at a time when a wild relative is receptive to it;
• crop pollen longevity, which can be minutes to hours;
• relative amount of pollen produced by the crop and wild relative;
• number of plants in the wild relative population near the crop;
• wild relative's pollination vector - wind, insects or both; and
• weather.  » More

In addition to a number of barriers to pollen flow, a successful cross- pollination requires fertilization. There are a number of barriers to that as well. Because of these barriers, viable crop pollen may reach a receptive wild relative but not be capable of fertilizing the egg.  » More

Even if pollen transfer and fertilization are successful, they are not sufficient for gene flow. This is because the plants must survive and produce offspring. This is difficult because of post-fertilization barriers to hybridization between different plants.  » More

For hybridization to lead to gene flow, the hybrid seeds produced by the cross- fertilization of the crop and wild relative must germinate into plants (hybrids) that contain the gene and are capable of reproduction.  » More

Because so many factors influence gene flow, assessing its likelihood requires looking at each crop on a case-by-case basis. This assessment must take into account, first and foremost, the presence or absence of wild relatives. If wild relatives occur where the crop derived through biotechnology is being grown, then we assess the potential for gene flow by evaluating the many factors influencing cross-pollination, fertilization and viable seed production. To illustrate the importance of a case-by-case approach, consider the relevant differences in DuPont's currently marketed crops derived through biotechnology: corn, canola and soybean.

Gene flow from corn, or maize, to wild plants is not an issue in the U.S., Canada or Europe because close relatives of corn grow only in Mexico and Central America. To determine the likelihood of gene flow from corn developed through biotechnology, we focus our assessment on corn growing in Mexico and Central America. We review the literature and do controlled field studies to determine relevant factors, such as:

• corn pollen production, movement and longevity;
• proximity of wild relatives to cornfield;
• tendency of wild relative to self-fertilize;
• compatible timing of corn pollen shedding and wild relative receptivity; and
• fertility of seeds produced from cross-fertilizations of crop and wild relative.

Gene flow to wild relatives is also not an issue for soybeans growing in the U.S., Canada or Europe, but becomes potentially important for soy grown in certain parts of China and Siberia, Taiwan, Korea, Japan, and Australia. Unlike corn, the relatives of soybean self-pollinate, or fertilize themselves, before the flower even opens. This means that the chance of other pollen fertilizing a plant is nearly nonexistent. In addition, gene flow would depend on a number of other factors, though the factors that further determine the extent of gene flow are less relevant for soybean than corn.

Oilseed, Brassica species, including quality canola species, have many wild relatives, some of which occur in most Brassica production regions of the world. Extensive research has been conducted within the last decade to assess the potential of gene flow from cultivated Brassica to wild relatives. This research focused on the potential of hybrid seed formation after cross-pollination of cultivated Brassica and wild relatives. The ability of such hybrid seed to grow into fertile plants was also taken into consideration to determine the likelihood of gene flow.  » More

Cross-pollination between a crop and a wild relative, giving rise to fertile hybrids, does not necessarily lead to adverse impacts on the environment or agricultural practices. In order to pose a problem, the genes added through biotechnology must become established in the wild plant population and enhance the ability of the new hybrids to out compete wild plants lacking the genes.

Adverse impacts become much more likely if hybrid plants survive better and reproduce more than wild plants lacking the crop gene. Certain crop genes could enhance survival and reproduction of the hybrids, while others would have no effect. Still others, such as crop genes that limit seed dispersal, place the hybrid at a competitive disadvantage when compared to wild plants. Therefore, to assess potential environmental impacts of gene flow, crop genes providing a competitive advantage must be looked at in conjunction with other crop genes, as well as specific environmental conditions. For example, genes for drought resistance could offer a competitive advantage. But, they would only be an advantage in areas where drought impacts the wild plant population.

However, successful hybridization and introgression of crop genes into wild relatives may lead in very rare circumstances to the crop gene becoming established in the wild plant population, even in the absence of a hybrid competitive advantage, when

• hybridization and introgression occur at a high rate, and
• the wild relative is a locally rare species.  » More

DuPont currently markets three crop varieties developed using biotechnology: soybean and canola that are tolerant to the herbicide glyphosate; and corn that provides protection against specific insect larvae that feed on corn and against the herbicides glufosinate and glyphosate. These products, sold under the Pioneer® brand, provide farmers with new crop management options and increased productivity. Before marketed, these products were rigorously tested and reviewed by regulatory authorities for food and feed safety, environmental impacts and product performance.

Gene flow from soybean is virtually non-existent, even in the regions of Asia where its wild relatives occur, because self-fertilization usually occurs before the flower opens, providing no opportunity for crop pollen to fertilize the wild relative. Therefore, it is not surprising that there has been only one documented case of cross- pollination between a conventionally bred soybean variety and a wild relative under natural conditions.  » More

If gene flow did occur from glyphosate tolerant soybean to wild relatives, the hybrids would have a competitive advantage over wild plants lacking the herbicide tolerance gene only if the wild plants were being controlled with glyphosate. If a wild plant population becomes resistant to glyphosate, it could still be controlled with many other herbicides on the market.  » More

A number of field studies in Mexico have documented the existence of hybrids of cultivated corn and its wild relative, teosinte. However, it appears that genes from cultivated corn have not become widespread or well established in teosinte populations. This is probably due to the hybrids also having acquired corn genes that prevent seed (kernel) dispersal. In order for genes from corn to have negative environmental impacts, the competitive advantage they provide the hybrids must overcome the very large disadvantage of limited seed dispersal. In the case of DuPont corn derived through biotechnology, which contains a gene that makes corn resistant to specific insect larvae, that shift to an overall advantage could occur only if the teosinte population was kept in check by the insect feeding. There is no evidence that this is the case.  » More

Numerous researchers have investigated the potential for oilseed Brassica species to cross with wild relatives. Some have shown that such hybrids could be produced under field conditions, but at a very low frequency. In virtually all cases, the chance to obtain hybrids was much higher when pollen flow was from wild to crop than from crop to wild. In addition, hybrids between cultivated Brassica and wild relatives produced offspring's that were less viable and fertile than their wild parent. Therefore, the likelihood of successful gene flow via pollination from Brassica crops to wild relatives is extremely low.  » More

Extensive research is being done to determine effective methods for decreasing or preventing gene flow from crops derived through biotechnology to wild relatives. Some involve non-technical solutions, such as assessing required isolation distances or using border rows of non-crops derived through biotechnology. Others evaluate the use of biotechnology to manage gene flow.