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Question

Have any engineered crop genes ended up in wild, weedy, or otherwise freeliving populations of crop relatives?

Submitted by: Norman C Ellstrand


Answer

Expert response from Michael Horak

Former Weed Resistance Platform Lead, Monsanto Company

Friday, 23/01/2015 13:05

In order for genes to move from one plant to another, cross pollination must occur.  Cross pollination among plants is a natural biological process that can occur between closely related plants. Generally, the more closely related two plant species are, the greater the chance that they can cross pollinate and hybridize with one another.  In rare cases cross pollination can occur between plants that are more distantly related (such as between different species, but almost never between plants in different genera).  However, when two different species cross pollinate it usually occurs at a much lower level than if they are the same species.  Any time cross pollination occurs and results in a viable seed, genes are moved to the offspring, but those offspring may not be very well adapted to persist as a “freeliving” population.  In order for any crop gene to move to a crop relative, the two species need to occur in the same location, flower at the same time, and be compatible with one another so that a viable offspring is produced.  Crop species vary in their ability to cross-pollinate; soybean is mostly self-pollinated, corn and alfalfa are mostly cross-pollinated, and canola and cotton have varying levels of cross pollination.

 

So to answer your question, “Have any engineered crop genes ended up in a wild, weedy, or otherwise free living populations of crop relatives?”  The answer is yes, this has occurred in very limited cases and to a very limited extent.  There have not been any negative environmental consequences as a result of these events. 

 

In order to explore this question further let us consider several of the main crops and the crop relatives to which they can potentially cross.  The main crops that have GM traits and compatible relatives include corn, soybean, cotton, canola and alfalfa.

 

The center of origin for corn is Mexico and Central America.  The wild relative of corn is teosinte.  To date there are no reports that indicate a GM trait has been detected in teosinte.  This is in part because GM corn is not currently commercially cultivated in Mexico and thus the potential for crossing is very limited.  Here is a response from my colleague in Mexico on the biodiversity in Mexico.

 

The center of origin for soybean is Asia, China and parts of Russia.  The wild relative of soybean is Glycine soja.  To date there are no reports that indicate that a GM trait has been detected in this species.  This is in part because GM soybean is not currently sold in these countries / region, and regardless the potential for outcrossing in soybean is very limited.  Since GM soybean is only imported and is handled in a confined handling system, the likelihood that soybean would be released, be able to grow, be in an area where Glycine soja grows, cross and produce viable offspring is very, very low.

 

Wild cotton is the same species as the cotton that is typically grown by most farmers.  Wild cotton occurs along the coastline growing on the sandy beaches in a few small regions of Mexico and the Caribbean.  These populations occur far from cultivated cotton which would limit the possibility for cross pollination with GM cotton.  Similar to corn and soybean there have been no reports of crossing to wild relatives after extensive study by several researchers.   

 

The potential for cross pollination from GM canola and related species has been extensively studied.  From these studies it is clear that most of canola’s wild relatives cannot cross in nature with canola to form viable offspring and when they do, the hybrids are often not well adapted to grow, survive and reproduce.  There is one case where GM canola and wild relatives of canola did cross in nature that serves as an example. 

 

In eastern Canada, hybrids of GM canola (Brassica napus) with a related species bird rape (Brassica rapa) were found at the margin of two cultivated fields.  These hybrids did not persist within the cultivated fields because the farmer used typical practices to control weeds and these plants were as susceptible to these practices as other crops and weeds.  Persistence was monitored for a period of several years and the hybrid plants with the GM trait drastically declined in density over a five year period but persisted at low levels at one of the two sites.  A single plant individual with the GM trait was found on the fifth year of monitoring but it had reduced fitness and fertility.  Thus, although hybrids between canola and bird rape may occur they are limited within cultivated fields because farmer management (e.g. tillage) limits their survival and these hybrids are not as fit as their parental species and have limited ability to persist outside of cultivated fields.