Transgene introgression from genetically modified crops to their wild relatives

Abstract

Transgenes engineered into annual crops could be unintentionally introduced into the genomes of their free-living wild relatives. The fear is that these transgenes might persist in the environment and have negative ecological consequences. Are some crops or transgenic traits of more concern than others? Are there natural genetic barriers to minimize gene escape? Can the genetic transformation process be exploited to produce new barriers to gene flow? Questions abound, but luckily so do answers.

Ecological Impacts of Genetically Modified Crops: Ten Years of Field Research and Commercial Cultivation

“…It is generally agreed that the hazards related to gene flow from GM crops are linked to the introgression of transgenes into populations of wild relatives [1,3,[97][98][99]. There is little scientific support for the assertion that transgene dispersal is a hazard in itself.…”

“…The process of introgression, however, is not this simple, and actually occurs in many steps involving several hybrid generations [99]. Gene flow can roughly be separated into two processes: hybridization and introgression.…”

“…Successful fertilization of the embryo must then be followed by zygote and seed formation. Introgression requires the hybrid seed to germinate and the first filial generation (F 1 ) plant to establish and flower in order to further hybridize with members of the recipient population [99,100]. F 1 hybrids must therefore persist for at least one generation and be sufficiently fertile to produce backcross hybrids.…”

“…The relative fitness of hybrids is depending both on the genotype and on the environmental conditions the hybrids are encountering. Transgenes that produce insect resistance (IR) will vary in their fitness potential-the common conclusion is that the transgenes will only confer a selective advantage if the fitness of wild populations is influenced by insect herbivores [98,99]. Some studies were able to confirm this hypotheses, e.g., F 1 hybrids of oilseed rape and Brassica rapa containing Bt-genes were found to have a fecundity advantage under high insect herbivore pressure [103,104].…”

“…To date, no long-term introgression of transgenes into wild populations leading to the extinction of any wild taxa has been observed [96,98,99]. Hybridization-mediated environmental impacts from the currently commercialized GM crops seem not to be any different from those of traditionally bred crops.…”