The Use of GM Crops in Developing Countries
Is the introduction of GM crops in developing countries consistent with a precautionary approach to biodiversity and human health?
Gene flow and biodiversity
4.28 The possibility that genes from GM crops may be transferred by pollen to other cultivars or wild relatives of the same kind of crop has caused concern. This phenomenon, termed gene flow, occurs frequently in nature where many plant species cross with related species to produce new kinds of plants.27 Gene flow is in part responsible for the wide variety of plants which have evolved over many thousands of years. It may, however, be undesirable where it leads to the transfer of specific unwanted traits, or to the permanent and irreversible transformation of a species or variety. While the possibility for gene flow exists for both non-GM and GM crops, some fear that gene flow from GM crops could endanger biodiversity in a new way. In particular, this could occur where a GM crop has been modified to include a gene from another type of organism (see case study 1 on Bt cotton, and case study 8 on the production of biopharmaceuticals).
4.29 In the UK there are no indigenous close relatives of crops such as maize or wheat, reducing the chances of negative consequences of gene flow. However, the situation is different in other countries. For example, in Mexico, gene flow between modern cultivated maize varieties and ancient landraces or wild relatives is likely to occur. Mexico is home to many different kinds of maize, and is a centre of diversity for the crop. The different varieties are used as raw material to improve the quality of maize varieties by farmers and plant breeders around the world. It is feared that the introduction of genetic material from GM maize varieties may have a negative impact.
4.30 Considerable interest was therefore aroused when researchers at the University of California at Berkeley published findings in 2001 which claimed that genes from GM maize had crossed into native Mexican maize landraces and become permanently established in their genetic material (an event known as ‘introgression’). The researchers further claimed that the transgenes were unstable and ‘seemed to have become re-assorted and introduced into different genomic backgrounds’.28 There are fears that these events could lead to unpredictable alterations in native maize. For example, a truncated promoter sequence might activate other genes. Some groups engaged in the monitoring of GM crops interpreted this as an instance of ‘genetic pollution’29 claiming that the ‘well had been poisoned’.30
4.31 While it was unclear how the GM maize might have been introduced in Mexico, where a ban on GM crops has been in place since 1999, subsequent debate about the scientific validity of the research led the journal Nature to disavow the published paper.31 The question of whether or not gene flow from GM maize had actually occurred was not disputed by any of the critics of the original paper and was subsequently supported by independent research.32 Debate centred around methodological issues concerning the study design and data analysis, which were used to support the claim that the alleged introgression was a significant threat to biodiversity.33
4.32 The possibility of gene flow from GM crops may indeed require special attention. However, we need to be clear about the precise characteristics of gene flow. First, the fact that a crop has been genetically modified to express a particular trait does not automatically mean that this trait confers a selective advantage in the wild. A specific trait may be present for a generation or two in wild plants, and then disappear, because other plants are more suited to the specific environment.34 Nonetheless, in some instances, selective advantage has been reported, for example, in GM insect-resistant rape seed.35 Possible risks would therefore depend largely on the particular crop and trait.
Footnotes27 Ellstrand NC, Prentice HC and Hancock J (1999) Gene flow and introgression from domesticated plants into their wild relatives, Annu Rev Ecol Syst 30: 539–63.
28 Quist D and Chapela I (2001) Transgenic DNA introgressed into traditional maize landraces in Oaxaca, Mexico, Nature 414: 541–3.
29 ETC Group (2002) Genetic Pollution in Mexico’s Center of Maize Diversity, in Backgrounder (Food First Institute for Food and Development Policy) Spring 2002.
30 GRAIN (2003) Poisoning the well: the genetic pollution of maize, in Seedling 20 Jan 2003.
31 (2002) Editorial note, Nature 416: 600.
32 In 2001, scientists of the Mexican National Institute of Ecology (INE) and the National Biodiversity Council (CONABIO) took randomised samples from 22 locations in Oaxaca and Puebla. The samples were split into two groups and analysed at the National Autonomous University of Mexico and the Centre for Investigation and Advanced Studies (CINVESTAV). Findings suggested that approximately 12% of the analysed plants contained transgenic promoters. In some areas, it was reported that up to 35% of the grain contained foreign sequences, see Mann CC (2002) Has GM corn ‘invaded’ Mexico?, Science 295: 1617–9. It is assumed that gene flow occurred as a consequence of illegal planting of GM maize amidst conventional maize varieties, see Advisory Committee on Releases to the Environment (ACRE) (2002) Report on an article concerning gene flow from genetically modified maize to native landraces in Mexico. Available: http://www.defra.gov.uk/environment/acre/advice/advice14.htm. Accessed on: 21 Oct 2003. See also AgBioWorld.org: Mexican Maize Resource Library. http://www.agbioworld.org/biotech_info/articles/mexmaizeresource.html. Accessed on: 21 Oct 2003.
33 Two communications criticising the original findings of Quist and Chapela appeared in Nature, see Metz M and Fütterer J (2002) Suspect evidence of transgenic contamination, Nature 416: 600–1; Kaplinsky N et al. (2002) Maize transgene results in Mexico are artefacts, Nature 416: 601; together with a reply by Quist and Chapela on page 602 of the same volume. It was later alleged that the criticisms by Metz & Fütterer and Kaplinski et al. were lacking objectivity since the researchers received funding from the company Syngenta. The letter appeared in a later volume of Nature, see Worthy K, Strohman RC and Billings PR (2002) Nature 417: 897; the same volume (pages 897–898) also includes a response by the accused researchers, addressing the allegation.
34 Brookes M (1998) Running wild, New Scientist 160 (2158): 38–41; Masood E (1999) UK gets the green light on modified crops, Nature 397: 286.
35 Stewart C et al. (1997) Increased fitness of transgenic insecticidal rapeseed under insect selection pressure, Mol Ecol 6: 773–9.