Abstract
In this review the primary strategies employed in compiling a risk assessment for gene flow from a GM crop to a wild crop relative are outlined. A risk is defined as the likelihood of harm resulting from exposure to the hazard. The spread of new genes and genetic exchange between crops and their wild relatives by introgressive hybridization has been a reality ever since the birth of agriculture. The significance of such gene flow has received little interest, however, until the advent of molecular biotechnology and the emergence of genetically modified (GM) crops. In principle, the scope for the transfer of certain, completely novel transgenes from GM crops into wild relatives means that there is an increased capacity for rapid jumps in the adaptation profile of the recipient. This capacity carries risks for the genetic integrity and evolutionary survival of the wild species, and of the survival of other species with which it coexists. In evaluating such potential problems, one must first define the unwanted outcomes (hazards) as clearly as possible, and then measure the likelihood of their occurrence (exposure). The assessment of risk can be compiled (Risk = hazard × exposure). Risk is estimated as the product of the probability of exposure, P ( E ), and the conditional probability of harm given that exposure has occurred, P ( H|E ). That is, R = P ( E ) x P ( H|E ). In measuring risks in this way, it is important to consider the management of the crop, the ecology, demography and population genetics of the wild species, the number, nature and location of the transgene(s) and the extent of introgression within the natural setting. Crucially, these assessments should be made against comparable risks posed by non-GM cultivars of the same crop (i.e. baseline data) so that judgements can be made concerning the significance of any change envisaged. Keywords: Conservation, Gene flow, Genetic resources, Hazards, Risks DOI : 10.7176/ALST/73-02 Publication date : April 30 th 2019
Highlights
Modern biotechnology has allowed the movement of genetic material across unrelated species, something impossible with the traditional breeding methods
Indirect hazards relate to the impact introgressed crop wild relatives (CWRs) have on other plants or animals that interact with the recipient species [2, 16]
The probability and consequences of gene flow to wild relatives is typically considered in the environmental risk assessment of genetically engineered crops
Summary
Modern biotechnology has allowed the movement of genetic material across unrelated species, something impossible with the traditional breeding methods. There are generally several possible unwanted ecological outcomes that require assessment from any particular GM cultivar whenever a cross-compatible wild relative is present [21, 22]. Direct hazards relate to the recipient itself and could include increased (or decreased) population size of the wild relative within its existing habitat, its invasion of a new habitat after acquisition of the crop gene(s) or a genetic sweep causing reduced allelic diversity in genes located around the transferred crop gene(s).
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